Ancient people teach us a thing or two about energy when they laid siege to an enemy town. Although we won’t do this today, we will explore some of the important physics concepts about energy that they have to teach us by making a simple catapult. We’re utilizing the “springy-ness” in the popsicle stick, spoon, and the torsion spring to fling the ball around the room. By moving the fulcrum as far from the ball launch pad as possible (on the catapult), you get a greater distance to press down and release the projectile.
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Materials
- tongue-depressor size popsicle stick
- clothespin
- plastic spoon
- scrap of cardboard of wood
- ping pong ball or wadded-up ball of aluminum foil (or something lightweight to toss, like a marshmallow)
- hot glue gun with glue sticks
Observations:
- What part of the catapult stores the most potential energy? Why is this?
- Where is the kinetic energy transferred to in this catapult?
- How would you make a catapult’s projectile travel farther?
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We're going to make a quick and easy drawing machine that will teach your kids about the conservation of energy! By storing energy in the rubber band (called "elastic potential energy"), you can see for yourself how this transforms into movement (called "kinetic energy") while making a picture on your paper.
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Materials:
- Rubber band
- Thread spool
- Marker or pen
- Large sheet of paper
- 3 paperclips or large washers
- First, thread your rubber band around a washer and secure it to the washer (or paperclip).
- Thread the rubber band through the thread spool.
- Insert the rubber band through two washers on the other end.
- Loop the rubber band around the marker so it sits flat against the two washers.
- Spin the marker around to wind up your machine and watch it draw!
Observations:
- What part of the drawing machine stores the potential energy?
- Where is the energy transferred in this machine?
- How would you make the drawing machine draw circles?
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Everything in the universe takes one of two forms: energy and matter. This experiment explores the idea that energy can never be created or destroyed, but it can transform. All the different forms of energy (heat, electrical, nuclear, sound etc.) can be broken down into two categories, potential and kinetic energy.
Think of potential energy the “could” energy. The battery “could” power the flashlight. The light “could” turn on. I “could” make a sound. That ball “could” fall off the wall. That candy bar “could” give me energy. Potential energy is the energy that something has that can be released. For example, the battery has the potential energy to light the bulb of the flashlight if the flashlight is turned on and the energy is released from the battery. Your legs have the potential energy to make you hop up and down if you want to release that energy (like you do whenever it’s time to do science!). The fuel in a gas tank has the potential energy to make the car move.
Kinetic energy is the energy of motion. Kinetic energy is an expression of the fact that a moving object can do work on anything it hits; it describes the amount of work the object could do as a result of its motion. Whether something is zooming, racing, spinning, rotating, speeding, flying, or diving… if it’s moving, it has kinetic energy. How much energy it has depends on two important things: how fast it’s going and how much it weighs.
We’re utilizing the elasticity of the rubber band to store potential energy to fling the ball around the room. The potential energy in the rubber band is transformed into kinetic energy of the moving ball when you hit the trigger to release the rubber band.
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Materials:
- two rubber bands
- one marshmallow
- one plastic ruler with a groove down the middle
- four brass fasteners
- five popsicle sticks
- wood clothespin
- two pegs (see video)
But what happens after you toss the ball?
When you simply drop a ball, it falls 16 feet the first second you release it. If you throw the ball using your marshmallow launcher, it will also fall 16 feet in the first second. The ball (or marshmallow) moves both away from you and down toward the ground once it’s released.
What if you throw it faster, and faster? Think about a bullet shot horizontally. It travels a lot faster than you can throw (about 2,000 feet each second). But it will still fall 16 feet during that first second, no matter how fast you fire it.
It’s because gravity pulls on all objects (like the ball and the bullet) the same way, no matter how fast they go. Catapults and marshmallow launchers like the one we just made are a nifty way to fire things both vertically and horizontally so you can get a better feel for how objects fly through the air. Notice when you launch how the balls always fall at the same rate.
After you have your launcher working, it’s time to measure some data and look at the physics behind this projectile motion. Let’s calculate the horizontal speed that your ball is traveling at, if you measured that it traveled 54 inches (4.5 ft), in 1.25 seconds.
To calculate the horizontal speed, we will use the following equation, where v is the horizontal speed, d is the horizontal distance, and t is time:
v = d / t
so if the ball traveled 20 feet in 4 seconds:
v = (20 ft) / 4 sec or
v = 5 ft/s
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Nothing says summer time fun than a home-built go-kart that can race down the driveway with just as much thrill as two story roller coasters.
A go-karts (also called "go-cart") can be gravity powered (without a motor) or include electric or gas powered motors. The gravity powered kind are also known as Soap Box Derby racers, and are the simplest kind to make since all you need is wheels, a frame, and a good hill (and a helmet!).
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Materials:
Hardware Bits and Pieces:
The go-kart we're going to make is long enough to hold two passengers, so feel free to shorten it up a bit if you're only needing it for one passenger. You'll need only a couple of tools like a drill and a saw, and also some experienced adult help and you'll be off and riding this vehicle in under two hours, from start to finish.
After you've got this working, you're probably going to be more than a little popular, especially with younger kids that might be too small to ride safely. Here's a smaller version you can build them with only a few parts. You'll not only get points for making something really cool, but it'll keep them busy so you can ride your new go-kart!
And yes, you must INSIST that everyone wears helmets, or you'll take the wheels off. Helmet hair is way more fashionable than squashed brain cells.
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- 4-6" wheels that do NOT swivel
- 3-5' rope
- two door hinges
- One 4-1/2" threaded hex head bolt with 4 washers and 2 nuts
- 2 heavy duty eye hooks
- Box of 1-1/2" long coarse threaded wood or drywall screws
- Six 3" long coarse threaded wood or drywall screws
-
- one piece that is 4" x 1" x 24"
- one piece that is 6" x 2" x 8 feet cut into three pieces (one 4' long piece and two pieces that are 2' long each)
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- Crescent wrench, open end wrenches, or socket wrench
- Saw for cutting wood to size
- Drill and drill bits (also a 1/2" bit)
- Measuring tape
- Pencil
If you’ve ever wondered how glow in the dark toys stay bright even in the dark, this activity is just for you! When light hits a material, it’s either reflected, transmitted, or absorbed as we discovered with the gummy bear activity earlier. However, certain materials will absorb one wavelength and emit an entirely different wavelength, and when this happens it’s called “fluorescence”. Let’s do an experiment first, and then we’ll go over why it does what it does.
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Materials
- Laser (green)
- Highlighter (pink or orange)
- Diffraction grating
- White paper
- Point your laser at the wall, making a bright green dot. (Red lasers won’t work with this experiment.)
- Look at the dot through the diffraction grating. What do you see? How many different colors are there? (If you don’t have a diffraction grating, then simply shine your laser onto a CD and look at the reflected beams.)
We’ll do more on diffraction another time, but just note that a diffraction grating is made up of a lot of tiny prisms that un-mix light into its different colors. That’s why you see several different dots coming from the laser when you pass it through the diffraction grating. If you look at a candle flame through a diffraction grating, you’ll see a whole rainbow, since the white light from a candle is made up of the rainbow. (Image below is a laser through a diffraction grating.) A laser is one color, monochromatic , so you should expect to see only one color through the diffraction grating.
Now let’s try something else…
- On your white sheet of paper, color an area with your marker.
- Hold the paper against the wall. You can tape it into place if that makes it easier.
- Turn off the lights and point a green laser at the highlighter area you colored in.
- Look at the dot next to the main dot through the diffraction grating.
- Do you see more than one color now? Whoa!
This is a fantastic experiment because it gives you totally unexpected results! Where did the colors come from when you shined your laser on the highlighter area? And why weren’t they present when you just used a plain white wall?
It has to do with something called fluorescence. When the green laser hits the orange square, the electrons are excited by the laser and jump up to a higher energy state, and then relax back down. When they relax down, they release photons (light particles) that are made up of several different wavelengths. The diffraction grating makes it possible to see those wavelengths individually as a spectrum.
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This lab is a physical model of what happens on Mercury when two magnetic fields collide and form magnetic tornadoes.
You’ll get to investigate what an invisible magnetic tornado looks like when it sweeps across Mercury.
Materials
- Two clear plastic bottles (2 liter soda bottles work well)
- Steel washer with a 3/8 inch hole
- Ruler and stopwatch
- Glitter or confetti (optional)
- Duct tape (optional)
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Download Student Worksheet & Exercises
- Determine the different water conditions, such as: changing the temperature, changing the volume (height of water), adding another molecule such as oil, isopropyl alcohol, vinegar, and dish soap, adding solid pieces such as glitter, salt, sugar, or small grains. The different mixtures will give different vortex rotation speeds and different drain times. This is equivalent to changing the atmosphere on Earth and seeing how it affects weather (not magnetic) tornadoes. Write the conditions you wish to test in the data table before you start.
- Fill one of the soda bottles with water using the data table. Set the bottle upright on the table.
- Set the washer on top of the bottle opening. Make sure there’s no cap on the bottle.
- Invert the empty bottle over the water‐filled bottle and line up the openings so they can be easily taped together. You want to tape them before they get wet with the washer between them.
- Place the two bottles on a table and watch the water drip from the top to the lower bottle as air bubbles move from bottom to top.
- Invert so the water is in the top bottle and circle it a couple of times to start a whirlpool in the bottle. You should see a vortex form inside as the top drains into the lower bottle. The hole in the vortex lets the airfrom the lower bottle flow easily into the upper bottle, so the upper drains easily.
- When you’ve finished, empty your bottle and add a different solution and repeat the experiment.
What's Going On?
Mercury looks peaceful at first glance. However, when you measure the surface with scientific instruments, you’ll see how the Sun blasts away any hope Mercury has of a thin atmosphere with its radiation and solar wind. Not only that, Mercury is ravaged by invisible magnetic tornadoes that start from the planet’s interior magnetic field. If you’ve ever experienced a tornado, you know how terrifying they can be. Now imagine they are the diameter of your entire planet.
These tornadoes are different from the Earth’s, which form when two weather systems smack into each other, creating instability in the atmosphere. The magnetic tornadoes on Mercury form when two magnetic fields collide. These monstrous cyclones form without warning and disappear within minutes.
Magnetic fields, like the Earth’s, are invisible shields that constantly protect us from the Sun. Our Earth is constantly being bombarded with high energy particles that are deflected off the magnetosphere of our planet. Mercury’s magnetic field is weak and it’s constantly being blasted by solar wind, which also carries a magnetic field. When these two fields collide, the magnetic fields spiral and twist to form a magnetic tornado. (Solar wind is a stream of high energy particles from the Sun’s outer atmosphere.)
Exercises
- Define an atmosphere.
- What is a magnetic field?
- Where do magnetic fields come from in planets?
- Which planets do not have a magnetic field?
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Using the position of the Sun, you can tell what time it us by making one of these sundials. The Sun will cast a shadow onto a surface marked with the hours, and the time-telling gnomon edge will align with the proper time.
In general, sundials are susceptible to different kinds of errors. If the sundial isn’t pointed north, it’s not going to work. If the sundial’s gnomon isn’t perpendicular, it’s going to give errors when you read the time. Latitude and longitude corrections may also need to be made. Some designs need to be aligned with the latitude they reside at (in effect, they need to be tipped toward the Sun at an angle). To correct for longitude, simply shift the sundial to read exactly noon when indicated on your clock. This is especially important for sundials that lie between longitudinal standardized time zones. If daylight savings time is in effect, then the sundial timeline must be shifted to accommodate for this. Most shifts are one hour.
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Download Student Worksheet & Exercises for ALL Sundials
Simple Sundial
- Index card
- Scissors
- Tape
- This sundial takes only a couple minutes to make, and reads easily for beginner students.
- Cut the template.
- Cut your index card into two triangles by cutting from one corner to the opposite diagonal corner. Stack the two triangles and tape together. This is called your gnomon.
- Tape the triangle to your 12-hour line, putting tape on both sides of the gnomon as you stick it to the paper.
- Put the sundial in a sunny place where it won’t be disturbed (like inside of a sunny window or on a table outdoors).
- Point the sundial so that the gnomon is pointing north. This is most easily done if you orient your sundial at exactly noon in your location. Line up the sundial with the Sun so that the shadow the gnomon makes lines up exactly with the 12.
- Tape the sundial down so it won’t move or get blown away.
- The gnomon must be exactly perpendicular to the hour markers. Use a ruler or a book edge to help you line this up.
Intermediate Sundial
- 2 yardsticks or metersticks
- Protractor
- Chalk
- Clock
- Find a sunny spot that has concrete and grassy area right next to each other. You’re going to poke the yardstick into the grass and draw on the concrete with chalk, so be sure that the concrete goes in an approximately east-west direction.
- First thing in the morning, stick one of the yardsticks into the dirt, right at the edge of the concrete.
- At the top of the hour (like at 8 a.m. or 9 a.m.), go out to your yardstick to mark a position.
- Lay the second yardstick down along the shadow that the upright yardstick makes on the ground. Use chalk to draw the shadow, and use the yardstick to make your line straight.
- Label this line with the hour.
- Set your timer and run back out at the top of the next hour.
- Repeat steps 3-6 until you finish marking your sundial.
- When you’ve completed your sundial, fill out the table.
Advanced Sundial
- Old CD (this can also be the transparent CD at the top of DVD/CD spindles)
- Empty CD Case
- Skewer
- Sticky tape
- Cardboard or small piece of clay
- Protractor
- Scissors
- Tape
- Hot glue
This sundial will work for all longitudes, but has a limited range of latitudes. If you live in the far north or far south, you’ll need to get creative about how to mount the CD so that the gnomon is pointed at the correct angle. For example, at the equator, the CD will lie flat (which is easy!), but near the north and south poles, the CD will be upside down.
- Cut out the timeline.
- Put a line of double-sided sticky tape along the back of the timeline. Extend the tape about ¼” (on the bottom edge) so it’s hanging off a paper a little.
- Flip the timeline over and roll the CD along this bottom edge, sticking the timeline to the edge of the CD. The timeline should be facing inward toward the center of the CD, perpendicular to the CD surface.
- Now it’s time to plug up the center hole. You can cut out circles from a CD and attach with tape, or use a small piece of clay.
- Push the skewer through the exact middle of the CD.
- Open up the CD case.
- Position the noon marker at the bottom and stick it using a piece of double-sided sticky tape or hot glue.
- The other side of the CD is glued to the CD case at the same angle as your latitude. For example, if I live at 43o north, I would use my protractor on the ground along the base of the CD case and lift the CD until the gnomon reads at 43o. Put a dab of hot glue to attach the CD to the lid of the case.
- Go outside and point the gnomon north (you may want to use a compass for this if it’s not noon.)
- The dial will have a shadow that falls on the timeline. You can read the time right off the timeline.
- For advanced students: Timeline correction: Do you remember how the Sun was fast or slow in the Stargazer’s Wall Chart from the lesson entitled: What’s in the Sky? That wavy line is called the Equation of Time, and you’ll need it to correct your sundial if you want to be completely accurate. This is a great demonstration for a Science Fair project, especially when you add a model of the Sun and Earth to help you explain what’s going on.
What’s Going On?
Sundials have been used for centuries to keep track of the Sun. There are different types of sundials. Some use a line of light to indicate what time it is, while others use a shadow.
Here are a couple of different models that, although they look a lot different from each other, actually all work to give the same results! Your sundial will work all days of the year when the Sun is out.
You’ll notice that north is the direction that your shadow’s length is the shortest. However, if you don’t know where east and west are, all you can do is know where north is. The equinox is a special time of year because the Sun rises in the exact east and sets in the exact west, making these two points exactly perpendicular with the north for your location (which they usually aren’t). At sunset, you can view your shadow (quickly before it disappears) and draw it with chalk on the ground, making a line that runs east-west. 90o CCW from the line is north.
In general, sundials are susceptible to different kinds of errors. If the sundial isn’t pointed north, it’s not going to work. If the sundial’s gnomon isn’t perpendicular, it’s going to give errors when you read the time. Latitude and longitude corrections may also need to be made. Some designs need to be aligned with the latitude they reside at (in effect, they need to be tipped toward the Sun at an angle). To correct for longitude, simply shift the sundial to read exactly noon when indicated on your clock. This is especially important for sundials that lie between longitudinal standardized time zones. The Equation of Time from the advanced lesson entitled: What’s in the Sky? can be used to correct for the Sun running slow or fast. Remember, this effect is due to both the Earth’s orbit not being a perfect circle and the fact that the tilt axis is not perpendicular to the orbit path. If daylight savings time is in effect, then the sundial timeline must be shifted to accommodate for this. Most shifts are one hour.
Exercises
- What kinds of corrections need to be made for your sundial?
- When wouldn’t your sundial work?
- How can you improve your sundial to be more accurate?
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Today you get to learn how to read an astronomical chart to find out when the Sun sets, when twilight ends, which planets are visible, when the next full moon occurs, and much more. This is an excellent way to impress your friends.
The patterns of stars and planets stay the same, although they appear to move across the sky nightly, and different stars and planets can be seen in different seasons.
Materials:
- Printout of Stargazer’s Almanac
- Pencil
- Tape and scissors (optional)
- Ruler
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Download Student Worksheet & Exercises
- If your chart comes on two pages, you’ll need to cut the borders off at the top and bottom and tape them together so they fit perfectly.
- Use your ruler as a straight edge to help locate items as you read the chart.
- Print out copies of the almanac by clicking the image of the Skygazer’s Almanac. You can print it full-size on two pages, or size it to fit onto a single page. Since there’s a ton of information on it, it’s best read over two pages. This is an expired calendar to practice with.
- First, note the “hourglass” shape of the chart. Do you see how it’s skinnier in the middle and wider near the ends? Since it’s an astronomical chart that shows what’s up in the sky at night, the nights are shorter during the summer months, so the number of hours the stars are visible is a lot less than during the winter. You’ll find the hours of the night printed across the top and bottom of the chart (find it now) and the months and days of the year printed on the right and left side.
- Can you find the summer solstice on June 20? Use your finger and start on the left side between June 17 and June 24. The 20th is between those two dates somewhere. Here’s how you tell exactly…
- Look at the entire chart – do you see the little dots that make up little squares all over the chart, like a grid? Each dot in the vertical direction represents one day. There are eight dots on the vertical side of the box.
- Let’s say you want to find out what time Neptune rises on June 17. Go back to June 17, which has its own little set of dots. Follow the dots with your finger until you hit the line that says Neptune Rises. Stop and trace it up vertically to the top scale to read just after 11 p.m.
- Look again at the dot boxes. Each horizontal dot is 5 minutes apart, and every six dots there is a vertical line representing the half-hour. The line crosses between the second and third dot, so if you lived in a place where you can clearly see the eastern horizon and looked out at 11:07, you’d see Neptune just rising. Since Uranus and Neptune are so far away, though, you’d need a telescope to see them. So let’s try something you can find with your naked eye.
- Look at Oct 21. What time does Saturn set? (5:30p.m.).
- What other two planets set right afterward? (Mercury at 6:03 p.m. and Mars sets at 7:12 p.m.).
- When does Jupiter rise? (7:32 p.m.).
- What is Neptune doing that night of Oct. 21? (Neptune transits, or is directly overhead, at 8:07 p.m. and sets at 1:30 a.m.)
- What other interesting things happen on Oct. 21? (Betelgeuse, one of the bright stars in the constellation Orion, rises at 9:23 p.m. Sirius, the dog star, rises at 11:06 p.m. The Pleiades, also known as the Seven Sisters, are overhead at 1:42 a.m.)
- Let’s find out when the Moon rises on Oct. 21. You’ll find a half circle representing the Moon centered on 11:05 p.m. Which phase is the Moon at? First or third quarter? (First. You can tell if you look at the next couple of days to see if the Moon waxes or wanes. Large circles indicate one of the four main phases of the Moon.)
- When does the Sun rise and set for Oct. 21? First, find the nearest vertical set of dots and read the time (5:30 p.m.). Now subtract out the 5-minute dots until you get to the edge. You should read three dots plus a little extra, which we estimate to be 17 minutes. Sunset is at 5:13 p.m. on Oct 21.
- Note the fuzzy, lighter areas on both sides of the hourglass. That represents the twilight time when it’s not quite dark, but it’s not daylight either. There’s a thin dashed line that runs up and down the vertical, following the curve of the hourglass offset by about an hour and 35 minutes. That’s the official time that twilight ends and the night begins.
- Can you find a meteor shower? Look for a starburst symbol and find the date right in the center. Those are the peak times to view the shower, and it’s usually in the wee morning hours. The very best meteor showers are when there’s also a new Moon nearby.
- Notice how Mercury and Venus stay close by the edges of the twilight. You’ll find a half-circle symbol representing the day that they are furthest from the Sun as viewed from the Earth, which is the best date to view it. For Venus, the * indicates the day that it’s the brightest.
- What do you think the open circle means at sunset on May 20? (New Moon)
- Students that spot the “Sun slow” or “Sun fast” marks on the chart always ask about it. It’s actually rather complicated to explain, but here’s the best way to think about it. Imagine that the vertical timeline running down the center means noon, not midnight. Do you see a second line weaving back and forth across the noon line throughout the year? That’s the line that shows the when the Sun crosses the meridian. On Feb 5, the Sun crosses that meridian at 12:14, so it’s “running slow,” because it “should have” crossed the meridian at noon. This small variation is due to the axis tilt of the Earth. Note that it never gets much more than 15 minutes fast or slow. The wavy line that represents this effect is called the Equation of Time. We’ll be using that later when we make our own sundials and have to correct for the Sun not being where it’s supposed to be.
- Look at Mars and Saturn both setting around the same time on Aug. 14. When two event lines cross, you’ll find nearby an open circle with a line coming from the top right side, accompanied by a set of arrows pointing toward each other. This means conjunction, and is a time when you can see two objects at once. Usually the symbol isn’t right at the intersection, because one of the objects is rising or setting and isn’t clearly visible. On Aug. 14, you’ll want to view them a little before they set, so the symbol is moved to a time where you can see them both more clearly.
- Important to note: If your area uses daylight savings time, you’ll need to add one hour to the times shown on the chart.
- Time corrections for advanced students: This chart was made for folks living on the 40o north latitude and 90o west longitude lines (which is Peoria, Ill.).
- If you live near the standardized longitudes for Eastern Time (75o), Central (90o), Mountain (105o) or Pacific (120o), then you don’t have to correct the chart times you read. However, if you live a little west or east of these standardized locations, you need a correction, which looks like this:
- For every degree west, add four minutes to the time you read off the chart.
- For every degree east, subtract four minutes from the time.
- For example, if you lived in Washington, D.C. (which is 77o longitude), note that this is 2o west of the Eastern Time, so you’d add 8 minutes to the time you read off the chart. Memorize your particular adjustment and always use it.
- If your latitude isn’t 40o north, then you need to adjust the rise and set times like this:
- If you live north of 40o, then the object you are viewing will be in the sky for longer than the chart shows, as it will rise earlier and set later.
- If you live south of 40o, then the object you are viewing will be in the sky for less time than the chart shows, as it will rise later and set earlier.
- The easiest way to calculate this is to note what time an object should rise, and then watch to see when it actually appears against a level horizon. This is your correction for your location.
What’s Going On?
This is one of the finest charts I’ve ever used as an astronomer, as it has so much information all in one place. You’ll find the rise and set times for all eight planets, peak times for annual meteor showers, moon phases, sunrise and set times, and it gives an overall picture of what the evening looks like over the entire year. Kids can clearly see the planetary movement patterns and quickly find what they need each night. I keep one of these posted right by the door for everyone to view all year long.
- If you live near the standardized longitudes for Eastern Time (75o), Central (90o), Mountain (105o) or Pacific (120o), then you don’t have to correct the chart times you read. However, if you live a little west or east of these standardized locations, you need a correction, which looks like this:
Exercises
- Is Mercury visible during the entire year?
- In general, when and where should you look for Venus?
- When is the best time to view a meteor shower?
- Which date has the most planets visible in the sky?
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Kepler’s Laws of planetary orbits explain why the planets move at the speeds they do. You’ll be making a scale model of the solar system and tracking orbital speeds.
Kepler’s 1st Law states that planetary orbits about the Sun are not circles, but rather ellipses. The Sun lies at one of the foci of the ellipse. Kepler’s 2nd Law states that a line connecting the Sun and an orbiting planet will sweep out equal areas in for a given amount of time. Translation: the further away a planet is from the Sun, the slower it goes.
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Download Student Worksheet & Exercises
What are the planets in our solar system starting closest to the Sun? On a sheet of paper, write down a planet and label it with the name. Do this for each of the eight planets.
- Mercury is 0.39 AU (in a rocket it would take 2.7 months to go straight to Mercury from the Sun)
- Venus is 0.72 AU
- Earth is 1 AU (in a rocket it would take 7 months to go straight to Earth from the Sun)
- Mars is 1.5 AU
- Jupiter is 5.2 AU
- Saturn is 9.6 AU
- Uranus is 19.2 AU
- Neptune is 30.1 AU (in a rocket it would take 18 years to go straight to Neptune from the Sun)
Of course, we don’t travel to planets in straight lines – we use curved paths to make use of the gravitational pull of nearby objects to slingshot us forward and save on fuel.
- Now draw the location of the asteroid belt.
- Draw the position of the Kuiper Belt” and ask a student to draw and label it (beyond Neptune).
- Where are the five dwarf planets? They are in the Kuiper belt and the asteroid belt:
- Ceres (in the Asteroid belt, closer to Jupiter than Mars)
- Pluto (is 39.44 AU from the Sun)
- Haumea (43.3 AU)
- Makemake (45.8 AU)
- Eris. (67.7 AU)
Now for the fun part! You’ll need a group of friends to work together for this lab, so you have at least one student for each planet, one for the Sun, and two for the asteroid belts, and five for the dwarf planets. You can assign additional students to be moons of Earth (Moon), Mars (Phobos and Deimos), Jupiter (assign only 4 for the largest ones: Ganymede, Callisto, Io, and Europa), Saturn (again, assign only 4: Titan, Rhea, Iapetus, and Dione), Uranus (Oberon, Titania), and Neptune (Triton). If you still have extra students, assign one to Charon (Pluto’s binary companion) and one each to Hydra and Nix, which orbit Pluto and Charon. While you ask the students to walk around in a later step, the moons can circle while they orbit.
- First, walk outside to a very large area.
- Hand the Sun student the measuring tape.
- Ask Kuiper Belt student(s) to take the end of the measuring tape and begin walking slowly away from the Sun.
- With each student assigned to the distance shown, grab the measuring tape and walk along with it. Please be careful – measuring tapes can have sharp edges! You can use gloves when you grab the tape if you’ve got a sharp steel measuring tape to protect your hands. Ask the Sun to call out the distances periodically so the students know when it’s time to come up.
- What do you notice about the distances between the planets? The nearest star is 114.5 miles away!
- Ask the students to let go of the measuring tape, except for Neptune and the Sun. Everyone else gathers around you (a safe distance away, as Neptune is going to orbit the Sun).
- Using a stopwatch, notice how much time it takes Neptune to walk around the Sun while holding the measuring tape taut. How long did it take for one revolution?
- Now ask Mercury to take their position on the tape at the appropriate distance. Time their revolution as they walk around the Sun. How long did it take?
- How does this relate to the data you just recorded for Neptune and Mercury? You should notice that the speeds the kids were walking at were probably nearly the same, but the time was much shorter for Mercury. If you could swing them around (instead of having them walk), can you imagine how this would make Mercury orbit at a faster speed than Neptune?
- If you have it, you can illustrate how Kepler’s 2nd law works and relate it back to this experiment. Tie a ball to the end of a string and whirling it around in a circle. After a few revolutions, let the string wind itself up around your finger. As the string length shortens, the ball speeds up. As the planet moves inward, the planet’s orbital speed increases. The planet’s speed decreases the further from the Sun it is located.
- Ask one of the bigger students to take their position with the measuring tape, reminding them to keep the tape taut no matter what happens. When they start to walk around the Sun, have the Sun move with them a bit (a couple of feet is good). Let the students know that the planet also yanks on the Sun just as hard as the Sun yanks on the planet. Since the planet is much smaller than the Sun, you won’t see as much motion with the Sun.
- Optional demonstration to illustrate this idea: take a heavy bag (I like to use oranges) and spin it around as you whirl around in a circle. Do you notice the student leans back a bit to balance themselves as they swing around and around? This is the same principle, just on a smaller scale. The two objects (the bag and the student) are orbiting around a common point, called the center of mass. In our real solar system, the Sun has 99.85% of the mass, so the center of mass lies inside the Sun (although not at the exact center).
- Look at the length of your measuring tape. Find the data table you need to use in the tables. Circle the one you’re going to use or cross out the ones you’re not.
- Using a stopwatch, time Venus as they walk around the Sun while holding the measuring tape taut. How long did it take for one revolution? (Make sure the Sun doesn’t move much during this process like they did for the demonstration. We’re assuming the Sun is at the center.)
- Continue this for all the planets.
What’s Going On?
Johannes Kepler, a German mathematician and astronomer in the 1600s, was one of the key players of his time in astronomy. Among his best discoveries was the development of three laws of planetary orbits. He worked for Tycho Brahe, who had logged huge volumes of astronomical data, which was later passed onto to Kepler. Kepler took this information to design and develop his ideas about the movements of the planets around the Sun.
Kepler’s 1st Law states that planetary orbits about the Sun are not circles, but rather ellipses. The Sun lies at one of the foci of the ellipse. Well, almost. Newton’s Laws of Motion state that the Sun can’t be stationary, because the Sun is pulling on the planet just as hard as the planet is pulling on the Sun. They are yanking on each other. The planet will move more due to this pulling because it is less massive. The real trick to understanding this law is that both objects orbit around a common point that is the center of mass for both objects. If you’ve ever swung a heavy bag of oranges around in a circle, you know that you have to lean back a bit to balance yourself as you swing around and around. It’s the same principle, just on a smaller scale.
In our solar system the Sun has 99.85% of the mass, so the center of mass between the Sun and any other object actually lies inside the Sun (although not at the center).
Kepler’s 2nd Law states that a line connecting the Sun and an orbiting planet will sweep out equal areas in for a given amount of time. The planet’s speed decreases the further from the Sun it is located (actually, the speed varies inversely with the square‐root of the distance, but you needn’t worry about that). You can demonstrate this to the students by tying a ball to the end of a string and whirl it around in a circle. After a few revolutions, let the string wind itself up around your finger. As the string length shortens, the ball speeds up. As the planet moves inward, the planet’s orbital speed increases.
Embedded in the second law are two very important laws: conservation of angular moment and conservation of energy. Although those laws might sound scary, they are not difficult to understand. Angular momentum is distance multiplied by mass multiplied by speed. The angular momentum for one case must be the same for the second case (otherwise it wouldn’t be conserved). As the planet moves in closer to the Sun, the distance decreases. The speed it orbits the Sun must increase because the mass doesn’t change. Just like you saw when you wound the ball around your finger.
Energy is the sum of both the kinetic (moving) energy and the potential energy (this is the “could” energy, as in a
ball dropped from a tower has more potential energy than a ball on the ground, because it “could” move if released). For conservation of energy, as the planet’s distance from the Sun increases, so does the gravitational potential energy. Again, since the energy for the first case must equal the energy from the second case (that’s what conservation means), the kinetic energy must decrease in order to keep the total energy sum a constant value.
Kepler’s 3rd Law is an equation that relates the revolution period with the average orbit speed. The important thing to note here is that mass was not originally in this equation. Newton came along shortly after and did add in the total mass of the system, which fixed the small error with the equation. This makes sense, as you might imagine a Sun twice the size would cause the Earth to orbit faster. However, if we double the mass of the Earth, it does not affect the speed with which it orbits the Sun. Why not? Because the Earth is soooo much smaller than the Sun that increasing a planet’s size generally doesn’t make a difference in the orbital speed. If you’re working with two objects about the same size, of course, then changing one of the masses absolutely has an effect on the other.
Exercises
- If the Sun is not stationary in the center but rather gets tugged a couple of feet as the planet yanks on it, how do you think this will affect the planet’s orbit?
- If we double the mass of Mars, how do you think this will affects the orbital speed?
- If Mercury’s orbit is normally 88 Earth days, how long do you estimate Neptune’s orbit to be?
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How do astronomers find planets around distant stars? If you look at a star through binoculars or a telescope, you’ll quickly notice how bright the star is, and how difficult it is to see anything other than the star, especially a small planet that doesn’t generate any light of its own! Astronomers look for a shift, or wobble, of the star as it gets gravitationally “yanked” around by the orbiting planets. By measuring this wobble, astronomers can estimate the size and distance of larger orbiting objects.
Doppler spectroscopy is one way astronomers find planets around distant stars. If you recall the lesson where we created our own solar system in a computer simulation, you remember how the star could be influenced by a smaller planet enough to have a tiny orbit of its own. This tiny orbit is what astronomers are trying to detect with this method.
Materials
- Several bouncy balls of different sizes and weights, soft enough to stab with a toothpick
- Toothpicks
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- Does your ball have a number written on it? If so, that’s the weight, and you can skip measuring the weight with a scale.
- If not, weigh each one and make a note in the data table.
- Take the heaviest ball and spin it on the table. Can you get it to spin in place? That’s like a Sun without any planets around it.
- Insert a toothpick into the ball. Now insert the end of the toothpick into the smallest weight ball. Now spin the original ball. What happened?
What’s Going On?
Nearly half of the extrasolar (outside our solar system) planets discovered were found by using this method of detection. It’s very hard to detect planets from Earth because planets are so dim, and the light they do emit tends to be infrared radiation. Our Sun outshines all the planets in our solar system by one billion times.
This method uses the idea that an orbiting planet exerts a gravitational force on the Sun that yanks the Sun around in a tiny orbit. When this is viewed from a distance, the star appears to wobble. Not only that, this small orbit also affects the color of the light we receive from the star. This method requires that scientists make very precise measurements of its position in the sky.
Exercises
- For homework tonight, find out how many extrasolar planets scientists have detected so far.
- Also for homework, find out the names (they will probably be a string of numbers and letters together) of the 3 most recent extrasolar planet discoveries.
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It just so happens that the Sun’s diameter is about 400 times larger than the Moon, but the Moon is 400 times closer than the Sun. This makes the Sun and Moon appear to be about the same size in the sky as viewed from Earth. This is also why the eclipse thing is such a big deal for our planet.
You’re about to make your own eclipses as you learn about syzygy. A total eclipse happens about once every year when the Moon blocks the Sun’s light. Lunar eclipses occur when the Sun, Moon, and Earth are lined up in a straight line with the Earth in the. Lunar eclipses last hours, whereas solar eclipses last only minutes.
Materials
- 2 index cards
- Flashlight or Sunlight
- Tack or needle
- Black paper
- Scissors
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- Trace the circle of your flashlight on the black paper and cut out the circle with paper. This is your Moon. If you are using the Sun instead, cut out a circle about the size of your fist.
- Make a tiny hole in one of the index cards by pushing a tack through the middle of the card.
- Hold the punched index card a couple inches above the plain one and shine your light through the hole so that a small disk appears on the lower card. Move the cards closer or further until it comes into focus. The disk of light is the Sun.
- Ask your lab partner to slowly move the black paper disk in front of your light as you watch what happens to the Sun on the bottom index card.
- Continue moving the black paper until you can see the Sun again.
- Where does your circle need to be in order to create an annular eclipse? A partial eclipse?
- How would you simulate Mercury transiting the Sun? What would you use?
- Fill out the table.
What’s Going On?
An eclipse is when one object completely blocks another. If you’re big on vocabulary words, then let the students know that eclipses are one type of syzygy (a straight line of three objects in a gravitational system, like the Earth, Moon, and Sun). A lunar eclipse is when the Moon moves into the Earth’s shadow, making the Moon appear copper-red.
A solar eclipse is when the Moon’s shadow crawls over the Earth, blocking out the Sun partially or completely. There are three kinds of solar eclipses. A total eclipse blocks the entire Sun, whereas in a partial eclipse the Moon appears to block part, but not all of the Sun’s disk. An annular eclipse is when the Moon is too far from Earth to completely cover the Sun, so there’s a bright ring around the Moon when it moves in front of the Sun. It just so happens that the Sun’s diameter is about 400 times larger than the Moon, but the Moon is 400 times closer than the Sun. This makes the Sun and Moon appear to be about the same size in the sky as viewed from Earth. This is also why the eclipse thing is such a big deal for our planet. Transits are where the disk of a planet (like Venus) passes like a small shadow across the Sun. Io transits the surface of Jupiter. In rare cases, one planet will transit another. These are rare because all three objects must align in a straight line.
Astronomers use this method to detect large planets around distant bright stars. If a large planet passes in front of its star, the star will appear to dim slightly. Note: A transit is not an occultation, which completely hides the smaller object behind a larger one. Exercises
- What other planets can have eclipses?
- Which planets transit the Sun?
- How is a solar eclipse different from a lunar eclipse?
- What phase can a lunar eclipse occur?
- Can a solar eclipse occur at night?
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A meteoroid is a small rock that zooms around outer space. When the meteoroid zips into the Earth’s atmosphere, it’s now called a meteor or “shooting star”. If the rock doesn’t vaporize en route, it’s called a meteorite as soon as it whacks into the ground. The word meteor comes from the Greek word for “high in the air.”
Meteorites are black, heavy (almost twice the normal rock density), and magnetic. However, there is an Earth-made rock that is also black, heavy, and magnetic (magnetite) that is not a meteorite. To tell the difference, scratch a line from both rocks onto an unglazed tile. Magnetite will leave a mark whereas the real meteorite will not.
Materials
- White paper
- Strong magnet
- Handheld magnifying glass (optional)
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- Imagine you are going on a rock hunt. You are to find which rocks are meteorites and which are Earth rocks. If you don’t have access to rock samples, just watch the experiment video of the different rock samples. If you’d like to make your own sample collection, here are some ideas:
- 8-10 different rocks, including pumice (from a volcano), lodestone (a naturally magnetized piece of magnetite, and often mistaken for meteorites), a fossil, tektite (dry fused glass), pyrite (also known as fool’s gold), marble (calcite or dolomite), and a couple of different kinds of real meteorites (iron meteorite, stony meteorite, etc.) Also add to your bag an unglazed tile and a magnet.
- As you watch the experiment video, record your observations on your data sheet.
- Since nearly all meteorites have lots of iron, they are usually attracted to a magnet. However, lodestone is an Earth rock that also has a lot of iron. Iron is heavy, and meteorites contain a lot of iron. When looking through the possibilities, remove any lightweight rocks, as they are not usually meteorites.
- Meteorites are small. Most never get big enough or hot enough for metal to sink into the core, so the majority are mixed with rock and dust (stony meteorites). The few that do get big and form metal cores are called iron meteorites.
- Most meteorites come from the Asteroid Belt. Some meteorites get a dark crust. While others look like splashed metal. They are all dark, at least on the outside. Remove any light-colored rocks.
- Rocks that have holes vaporize or explode when they go through the atmosphere, they don’t burn up. Only strong space rocks without holes make it to the ground. Remove any porous rocks.
- The ones you have left are either meteorites or lodestone. To tell the difference, scratch a line from both rocks onto an unglazed tile. Magnetite (lodestone) will leave a mark whereas the real meteorite will not.
Finding Meteorites
- Place a sheet of white paper outside on the ground. Do this in the morning when you first start up class.
- After a few hours (like just before lunchtime), your paper starts to show signs of “dust.”
- Carefully place a magnet underneath the paper, and see if any of the particles move as you wiggle the magnet. If so, you’ve got yourself a few bits of space dust.
- Use a magnifying lens to look at your space meteorites up close.
What’s Going On?
94% of all meteorites that fall to the Earth are stony meteorites. Stony meteorites will have metal grains mixed with the stone that are clearly visible when you look at a slice.
Iron meteorites make up only 5% of the meteorites that hit the Earth. However, since they are stronger, most of them survive the trip through the atmosphere and are easier to find since they are more resistant to weathering. More than half the meteorites we find are iron meteorites. They are the one of the densest materials on Earth. They stick strongly to magnets and are twice as heavy as most Earth rocks. The Hoba meteorite in Namibia weighs 50 tons.
Since nearly all meteorites have lots of iron, they are usually attracted to a magnet. However, lodestone is an Earth rock that also has a lot of iron. Iron is heavy, and meteorites contain a lot of iron. When looking through the possibilities, remove any lightweight rocks, as they are not usually meteorites.
Meteorites are small. Most never get big enough or hot enough for metal to sink into the core, so the majority are mixed with rock and dust (stony meteorites). The few that do get big and form metal cores are called iron meteorites.
Most meteorites come from the Asteroid Belt. Some meteorites get a dark crust, while others look like splashed metal. They are all dark, at least on the outside.
Rocks that have holes vaporize or explode when they go through the atmosphere, they don’t burn up. Only strong space rocks without holes make it to the ground.
Every year, the Earth passes through the debris left behind by comets. Comets are dirty snowballs that leave a trail of particles as they orbit the Sun. When the Earth passes through one of these trails, the tiny particles enter the Earth’s atmosphere and burn up, leaving spectacular meteor showers for us to watch on a regular basis. The best meteor showers occur when the moon is new and the sky is very dark.
Meteorites are black, heavy (almost twice the normal rock density), and magnetic. However, there is an Earth-made rock that is also black, heavy, and magnetic (magnetite) that is not a meteorite. To tell the difference, scratch a line from both rocks onto an unglazed tile (or the bottom of a coffee mug or the underside of the toilet tank). Magnetite will leave a mark, whereas the real meteorite will not.
If you find a meteorite, head to your nearest geology department at a local university or college and let them know what you’ve found. In the USA, if you find a meteorite, you get to keep it… but you might want to let the experts in the geology department have a thin slice of it to see what they can figure out about your particular specimen.
Exercises
- Are meteors members of the solar system?
- How big are meteors?
- Why do we have meteor showers at predictable times of the year?
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You are going to start observing the Sun and tracking sunspots across the Sun using one of two different kinds of viewers so you can figure out how fast the Sun rotates. Sunspots are dark, cool areas with highly active magnetic fields on the Sun’s surface that last from hours to months. They are dark because they aren’t as bright as the areas around them, and they extend down into the Sun as well as up into the magnetic loops.
Materials
- Tack and 2 index cards OR a Baader film (this works better than the tacks and card)
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We’re going to learn two different ways to view the Sun. First is the pinhole projector and the second is using a special film called a Baader filter. The quickest and simplest way to do this is to build a super-easy pinhole camera that projects an image of the Sun onto an index card for you to view.
If the Sun is not available, you can use images from a satellite that’s pointed right at the Sun while orbiting around the Earth called “SOHO.” SOHO gets clear, unobstructed views of the Sun 24 hours a day, since it’s above the atmosphere of the Earth. Download the very latest image of the Sun from NASA’s SOHO page (choose the SDO/HMI Continuum filter for the best sunspot visibility) and hand them out to the students to track the sunspots.
Solar Pinhole Projector
- With your tack, make a small hole in the center of one of the cards.
- Stack one card about 12″ above the other and go out into the Sun.
- Adjust the spacing between the cards so a sharp image of the Sun is projected onto the lower paper.
- The Sun will be about the size of a pea.
- You can experiment with the size of the hole you use to project your image.
- What happens if your hole is really big? Too small?
- What if you bend the lower card while viewing? What if you punch two holes? Or three?
Baader Filter
- Using a Baader filter, you’re going to look straight through the filter right at the Sun. Put the filter between you and the Sun, right up close to your eye and look through it. It takes a little while to get the hang of seeing the Sun through this filter, but it’s totally worth it.
Taking Data:
- Using either the Baader filter or the solar pinhole projector (or both), you will track the sunspot activity using the mapping grid. You will be charting the Sun for two weeks using the mapping grid.
- Each day, step outside at the same time each day and look at the Sun using one of the two filter methods.
- Draw what you see on the mapping grid.
- Draw the sunspot(s) with the date of the month next to it. For example, on March 13, write a “13” right next to the sunspot picture you drew. If there’s more than one sunspot, pick the largest one to track. If you’d like to track all of them, label them A-13, B-13, C-13…etc. The next day, label the set A-14, B-14, C-14. For multiple sunspots, use one mapping grid per day.
What’s Going On?
The Sun rotates differentially, since it’s not solid but rather a ball of hot gas and plasma. The equator rotates faster than the poles, and in one of the experiments in this section, you’ll actually get to measure the Sun’s rotation. This differential rotation causes the magnetic fields to twist and stretch. The Sun has two magnetic poles (north and south) that swap every 11 years as the magnetic fields reach their breaking point, like a spinning top that’s getting tangled up in its own string. When they flip, it’s called “solar maximum,” and you’ll find the most sunspots dotting the Sun at this time.
You know you’re not supposed to look at the Sun, so how can you study it safely? I’m going to show you how to observe the Sun safely using a very inexpensive filter. I actually keep one of these in the glove box of my car so I can keep track of certain interesting sunspots during the week!
The visible surface of the Sun is called the photosphere, and is made mostly of plasma (electrified gas) that bubbles up hot and cold regions of gas. When an area cools down, it becomes darker (called sunspots). Solar flares (massive explosions on the surface), sunspots, and loops are all related the Sun’s magnetic field. While scientists are still trying to figure this stuff out, here’s the latest of what they do know…
The Sun is a large ball of really hot gas – which means there are lots of naked charged particles zipping around. And the Sun also rotates, but the poles and the equator move and different speeds (don’t forget – it’s not a solid ball but more like a cloud of gas). When charged particles move, they make magnetic fields (that’s one of the basic laws of physics). And the different rotation rates allow the magnetic fields to “wind up” and cause massive magnetic loops to eject from the surface, growing stronger and stronger until they wind up flipping the north and south poles of the Sun (called ‘solar maximum’). The poles flip every 11 years.
The Sun rotates, but because it’s not a solid body but a big ball of gas, different parts of the Sun rotate at different speeds. The equator (once every 27 days) spins faster than the poles (once every 31 days). Sunspots are a great way to estimate the rotation speed.
Sunspots usually appear in groups and can grow to several times the size of the Earth. Galileo was the first to record solar activity in 1613, and was amazed how spotty the Sun appeared when he looked at the projected image on his table.
There have been several satellites especially created to observe the Sun, including Ulysses (launched 1990, studied solar wind and magnetic fields at the poles), Yohkoh (1991-2001, studied X-rays and gamma radiation from solar flares), SOHO (launched 1995, studies interior and surface), and TRACE (launched 1998, studies the corona and magnetic field). And as of August 2017, Astronomers have figured out that the surface of the sun rotates slower than its core (by about four times as much!) by studying surface acoustic waves in the sun’s atmosphere.
Exercises
- How many longitude degrees per day does the sunspot move?
- Do all sunspots move at the same rate?
- Did some of the sunspots change size or shape, appear or disappear?
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Have you ever wondered why the sky is blue? Or why the sunset is red? Or what color our sunset would be if we had a blue giant instead of a white star? This lab will answer those questions by showing how light is scattered by the atmosphere.
Particles in the atmosphere determine the color of the planet and the colors we see on its surface. The color of the star also affects the color of the sunset and of the planet.
Materials
- Glass jar
- Flashlight
- Fingernail polish (red, yellow, green, blue)
- Clear tape
- Water
- Dark room
- Few drops of milk
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- Make your room as dark as possible for this experiment to work.
- Make sure your label is removed from the glass jar or you won’t be able to see what’s going on.
- Fill the clear glass jar with water.
- Add a teaspoon or two of milk (or cornstarch) and swirl.
- Shine the flashlight down from the top and look from the side – the water should have a bluish hue. The small milk droplets scatter the light the same way our atmosphere’s dust particles scatter sunlight.
- Try shining the light up from the base – where do you need to look in order to see a faint red/pink tint? If not, it’s because you are looking for hues that match our real atmosphere, and the jar just isn’t that big, nor is your flashlight strong enough! Instead, look for a very slight color shift. If you do this experiment after being in the dark for about 10 minutes (letting your eyes adjust to the lack of light), it is easier to see the subtle color changes. Just be careful that you don’t let the brilliant flashlight ruin your newly acquired night-vision, or you’ll have to start the 10 minutes all over again.
- If you are still having trouble seeing the color changes, shine your light through the jar and onto an index card on the other side. You should see slight color changes on the white card.
- Cover the flashlight lens with clear tape.
- Paint on the tape (not the lens) the fingernail polish you need to complete the table.
- Repeat steps 7-9 and record your data.
What’s Going On?
Why is the sunset red? The colors you see in the sky depends on how light bounces around. The red/orange colors of sunset and sunrise happen because of the low angle the Sun makes with the atmosphere, skipping the light off dust and dirt (not to mention solid aerosols, soot, and smog). Sunsets are usually more spectacular than sunrises, as more “stuff” floats around at the end of the day (there are less particles present in the mornings). Sometimes just after sunset, a green flash can be seen ejecting from the setting Sun.
The Earth appears blue to the astronauts in space because the shorter, faster wavelengths are reflected off the upper atmosphere. The sunsets appear red because the slower, longer wavelengths bounce off the clouds.Sunsets on other planets are different because they are farther (or closer) to the Sun, and also because they have a different atmosphere than planet Earth. The image shown here is a sunset on Mars. Uranus and Neptune appear blue because the methane in the upper atmosphere reflects the Sun’s light and the methane absorbs the red light, allowing blue to bounce back out.
Exercises
- What colors does the sunset go through?
- Does the color of the light source matter?
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One common misconception is that the seasons are caused by how close the Earth is to the Sun. Today you get to do an experiment that shows how seasons are affected by axis tilt, not by distance from the Sun. And you also find out which planet doesn’t have sunlight for 42 years.
The seasons are caused by the Earth’s axis tilt of 23.4o from the ecliptic plane.
Materials
- Bright light source (not fluorescent)
- Balloon
- Protractor
- Masking tape
- 2 liquid crystal thermometers (optional)
- Ruler, yardstick or meter stick
- Marker
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- For a light source, try lamps with 100W bulbs (without lamp shades). Make sure there’s room to walk all the way around it. You’ll want to circle the lamp at a distance of about 2 feet away.
- Mark on the floor with tape and label the four positions: winter, spring, summer, and fall. They should be at the 12, 3, 6, and 9 o’clock positions. Winter is directly across from summer. The Earth rotates counterclockwise around the Sun when viewed from above.
- Blow up your balloon so it’s roughly round-shaped (don’t blow it up all the way). Mark and label the north and south poles with your marker. Draw an equator around the middle circumference.
- The Earth doesn’t point its north pole straight up as it goes around the Sun. It’s tilted over 23.4o. here’s how you find this point on your balloon:
- Put the South Pole mark on the table, with north pointing straight up. Find the midway point between the equator and the North Pole and make a tiny mark. This is the 45o latitude point. You’ll need this to find the 23o mark.
- Find the midway point between the 45o and the North Pole and make another mark, larger this time and label it with 23o. When this mark is pointing up, the Earth is tilted over the right amount.
- You’ll need to do this three more times so you can draw a line connecting the dots. You want to draw the latitude line at 23o so you can rotate the balloon as you move around to the different seasons. The line will always be pointed up.
- Place the thermometers on the balloon at these locations:
- Find the halfway point between the South Pole and the equator. Put one thermometer on this mark.
- Put the other thermometer on the northern hemisphere’s 45o mark from above.
- Make sure your lamp is facing the balloon as you stand on summer. Let the balloon be heated by the lamp for a couple of minutes and then record the temperature in the data table.
- Rotate the lamp to point to fall. Move your balloon to fall, rotating the balloon so that the thermometers are facing the lamp. Wait a few more minutes and take another reading.
- Rotate the lamp to point to winter. Move your balloon to winter, rotating the balloon so that the thermometers are facing the lamp. Wait a few more minutes and take another reading.
- Rotate the lamp to point to spring. Move your balloon to spring, rotating the balloon so that the thermometers are facing the lamp. Wait a few more minutes and take another reading. You’ve completed a data set for planets with an axis tilt of about 23o, which includes the Earth, Mars, Saturn and Neptune.
- Repeat steps 1-9 for Mercury. Note that Mercury does not have an axis tilt, so the North Pole really points straight up. Jupiter (3.1o axis tilt) and Venus (2.7o) are very similar. The Moon’s axis tilt is 6.7o, so you can approximate these four objects with a 0o axis tilt.
- Repeat steps 1-9 for Uranus. Since the axis tilt is 97.8o, you can approximate this by pointing the north pole straight at the Sun during summer (90o axis tilt). The orbit for Uranus is 84 years, which means 21 years passes between each season. The north pole will experience continued sunlight for 42 years from spring through fall, then darkness for 42 years.
What’s Going On?
The north and south poles only experience two seasons: winter and summer. During a South Pole winter, the Sun will not rise for several months, and also the Sun does not set for several months in the summer. We go into more detail about how this works in a later lesson entitled: Star Trails and Planet Patterns.
At the equator, there’s a wet season and a dry season due to the tropical rain belt. Since the equator is always oriented at the same position to the Sun, it receives the same amount of sunlight and always feels like summer.
The changing of the seasons is caused by the angle of the Sun. For example, in June during summer solstice, the Sun is high in the sky for longer periods of time, which makes warmer temperatures for the Northern Hemisphere. During the December winter solstice, the Sun spends less time in the sky and is positioned much lower. This makes the winters colder. (Don’t forget that seasons are also affected by oceans and winds, though this is out of the scope of this particular activity.)
Exercises
- What is the main reason we have seasons on Earth?
- Why are there no sunsets on Uranus for decades?
- Are there seasons on Venus?
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On a clear night when Jupiter is up, you’ll be able to view the four moons of Jupiter (Europa, Ganymede, Io, and Callisto) and the largest moon of Saturn (Titan) with only a pair of binoculars. The question is: Which moon is which? This lab will let you in on the secret to figuring it out.
You get to learn how to locate a planet in the sky with a pair of binoculars, and also be able to tell which moon is which in the view.
Materials
- Printout of corkscrew graph
- Pencil
- Binoculars (optional)
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Download Student Worksheet & Exercises
- Look at your corkscrew satellite graph. These are common among astronomers for both Saturn and Jupiter. Notice how Saturn has a lot more wavy lines than Jupiter. We’re going to focus on Jupiter for the first part of this lab. Jupiter’s graph is the one on the left with Ganymede as one of the moons.
- The wavy lines represent four of Jupiter’s biggest moons: Ganymede, Callisto, Europa, and Io. The central two lines for a band is the width of Jupiter itself. If you see any gaps in the wavy lines, those are times when the moon is behind Jupiter. Each bar across that corresponds to a number is an entire day. The width of the column represents how far away each moon is from Jupiter. Notice at the top it says East and West.
- Draw a circle that represents Jupiter.
- Notice the largest waves are made by Callisto. Who makes the smallest waves? (Io.)
- Look at Dec 4th. Which moons are on which side of Jupiter? (Ganymede is the furthest east, and Io is closer to the planet, still on the east side. On the west, Europa is closer to Jupiter than Callisto.)
What’s Going On?
Jupiter’s Rings and Moons
Jupiter’s moons are threadlike when compared with Saturn’s. Also, unlike Saturn’s rings, Jupiter’s rings come from ash spewed out from the active volcanoes of its moons. Since Jupiter is so large, its gravity likes to catch things. When a volcano shoots its ash-snow up, Jupiter grabs it and swirls it in on itself. The moons are constantly replenishing the rings, which is why they are so much smaller than Saturn’s and much harder to detect (you won’t see them with binoculars or a backyard telescope).
If you’re doing the binocular portion of this lab in the evening, the numbers on binoculars refer to the magnification and the lens at the end. For example, 7×50 means you’re viewing the sky at 7X, and the lenses are at 50mm. Most people can easily hold up to 10x50s before their arms get tired. Remember, you’re looking up, not out or down as in normal terrestrial daytime viewing.
Saturn’s Rings and Moons
Galileo Galilei was the first to point a telescope at the sky, and the first to glance at the rings of Saturn in 1610. In the 1980s, the Voyager 1 and Voyager 2 spacecraft flew by, giving us our first real images of the rings of Saturn. Some of the biggest mysteries in our solar system are: What are the rings made up of, and why?
The Cassini-Huygens Mission answered the first question: The rings are made of billions of particles ranging from dust-sized icy grains to a couple of mountain-sized chunks. Actually, Saturn’s rings are an optical illusion. They are not solid, but rather a blizzard of water-ice particles mixed with dust and rock fragments, and each piece orbits Saturn like a little a moon. These billions of particles race around Saturn in tracks, and are herded into position by moons that also orbit within the rings (“shepherd” moons). Shepherd moon Pan orbits in the Encke gap, Daphnis orbits in the Keeler gap, Atlas orbits in the A ring, Prometheus in the F ring, and Pandora in the F ring. These moons keep the gaps open with their gravity.
The second question is harder to answer, but the latest news is that the rings are pieces of comets, asteroids or shattered moons that broke apart before they ever reached Saturn. Although each ring orbits at a different speed around the planet, the Cassini spacecraft had to slow down to 75,000 mph before it dropped into the rings to orbit around the planet.
While the rings are wide enough to see with a backyard telescope, the main rings (A, B and C) are paper-thin, only 10 meters (33 feet) thick.
Uranus and Neptune are called ice giants because of the amounts of ice in their atmospheres. Their atmospheres are also made of mostly hydrogen and helium.
Cassini found that a great plume of icy material blasting from the moon Enceladus is a major source of material for the expansive E ring. Additionally, Cassini has found that most of the planet’s small, inner moons appear to orbit within partial or complete rings formed from particles blasted off their surfaces by impacts of micrometeoroids.
Exercises
- Find a date that has all four moons on one side of Jupiter.
- When is Callisto in front of Jupiter and Io behind Jupiter at the same time?
- Are the images you’ve drawn in the table what you’d expect to see in binoculars, or are they upside down, mirrored, or inverted?
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If you want to get from New York to Los Angeles by car, you’d pull out a map. If you want to find the nearest gas station, you’d pull out a smaller map. What if you wanted to find our nearest neighbor outside our solar system? A star chart is a map of the night sky, divided into smaller parts (grids) so you don’t get too overwhelmed. Astronomers use these star charts to locate stars, planets, moons, comets, asteroids, clusters, groups, binary stars, black holes, pulsars, galaxies, planetary nebulae, supernovae, quasars, and more wild things in the intergalactic zoo.
How to find two constellations in the sky tonight, and how to get those constellations down on paper with some degree of accuracy.
Materials
- Dark, cloud-free night
- Two friends
- String
- Rocks
- Pencil
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Download Student Worksheet & Exercises
- Tape your string to the pencil.
- Loosely wrap the string around your finger several times so that the tip of the pencil is about an inch above the ground.
- Find a constellation. Point to a star in the constellation.
- Have a second person place a rock under the pencil tip.
- When they’ve placed the rock in position, point to another star.
- Have a second person place a rock under the pencil tip again.
- Repeat this process until all the stars have rocks under their positions.
- You should see a small version of the constellation on your paper.
What’s Going On?
People have been charting stars since long before paper was invented. In fact, we’ve found star charts on rocks, inside buildings, and even on ivory tusks. Celestial cartography is the science of mapping the stars, galaxies, and astronomical objects on a celestial sphere.
Celestial navigation (astronavigation) made it possible for sailors to cross oceans by sighting the Sun, moon, planets, or one of the 57 pre-selected navigational stars along with the visible horizon.
Watch the video that shows how the stars appear to move differently, depending on which part of the Earth you’re viewing from. What’s the difference between living on the equator or in Antarctica (explained in video)?
The first thing to star chart is the Big Dipper, or other easy-to-find constellation (alternates: Cassiopeia for northern hemisphere or the Southern Cross for the southern hemisphere). The Big Dipper is always visible in the northern hemisphere all year long, so this makes for a good target.
Use glow–in-the-dark stars instead of rocks, and charge them with a quick flash from a camera (or a flashlight). Keep your hand as still as you can while the second person lines the rock into position. You can also unroll a large sheet of (butcher or craft) paper and use markers to create a more permanent star chart.
Exercises:
- If you have constellations on your class ceiling, chart them on a separate page marking the positions of the rocks with X’s.
- Tonight, find two constellations that you will chart. Bring them with you tomorrow using the technique outlined above in Experiment.
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When high energy radiation strikes the Earth from space, it’s called cosmic rays. To be accurate, a cosmic ray is not like a ray of sunshine, but rather is a super-fast particle slinging through space. Think of throwing a grain of sand at a 100 mph… and that’s what we call a ‘cosmic ray’. Build your own electroscope with this video!
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Materials:
- Clean glass jar with a lid
- Wire coat hanger and sand paper
- Aluminum foil
- Vice grips or a hacksaw
- Scissors
- Balloon or other object to create a static charge
- Hot glue gun (optional)
Download Student Worksheet & Exercises
Troubleshooting: This device is also known as an electroscope, and its job is to detect static charges, whether positive or negative. The easiest way to make sure your electroscope is working is to rub your head with a balloon and bring it near the foil ball on top – the foil “leaves” inside the jar should spread apart into a V-shape.
Exercises
- How does this detector work?
- Do all particles leave the same trail?
- What happens when the magnet is brought close to the jar?
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The stars rise and set just like our sun, and for people in the northern hemisphere, the Big Dipper circles the north star Polaris once every 24 hours. Would you like to learn how to tell time by the stars?
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From the northern hemisphere, the Big Dipper is above the horizon for most of the year. In the spring time (especially in March), it’s fun and easy to learn how to tell time by the stars!
First, go outside after sunset and find the Big Dipper. Use a compass if you need to to find NORTH, then tilt your head back and look up from the horizon for seven bright stars.
Draw a line through two bowl stars (furthest from the handle) and extend that line so it hits the north “pole” star Polaris.
The “sky clock” is a 24-hour clock, not a 12-our clock like the one in your house. Polaris is the center of the clock, and the hour hand is the line you drew from the Big Dipper to Polaris.
Now use this simple formula: The current TIME = the clock reading MINUS twice the number of months after March 6. (You can use March 1 to make it easier to figure out.) Imagine we’re in March right now, so that “number of months past March” is ZERO. (See why it’s easy in March?) So go look up at the sky clock and read what time it is!
Notice how we read the sky clock COUNTERCLOCKWISE. This is opposite of the clock in your kitchen.
Let’s take another example. Suppose it’s Dec. 1st.
Dec 1 is close to Dec 6, so let’s figure about 9 months (to be exact, it would be 8.75 months, but let’s make it easy to calculate this time through). The night sky looks like the second image (without the clock superimposed over it). Can you tell me what time it is?
ANSWER:
The clock reads 2PM. The correction is 2 x 9 = 18. That is 18 hours we will need to SUBTRACT from 2PM.
So the time I read on the clock is about 2am (you could say 1:30am, but I am trying to make it easier here).
Now subtract 12 hours to make that PM into AM.
Now we only need to subtract 6 more hours.
Subtract 6 hours from 2AM to get 8PM!
The more you practice this, the easier it will be!
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The Moon appears to change in the sky. One moment it’s a big white circle, and next week it’s shaped like a sideways bike helmet. There’s even a day where it disappears altogether. So what gives?
The Sun illuminates half of the Moon all the time. Imagine shining a flashlight on a beach ball. The half that faces the light is lit up. There’s no light on the far side, right? For the Moon, which half is lit up depends on the rotation of the Moon. And which part of the illuminated side we can see depends on where we are when looking at the Moon. Sound complicated? This lab will straighten everything out so it makes sense.
Materials
- ball
- flashlight
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This first video will show you how the moon changes it’s appearance over the course of its cycle:
This video will show you how to demonstrate why the moon changes it’s appearance over the course of its cycle:
Download Student Worksheet & Exercises
- This lab works best if your room is very dark. Button down those shades and make it as dark as you can.
- Assign one person to be the Sun and hand them the flashlight. Stay standing up about four feet away from the group. The Sun doesn’t move at all for this activity.
- Assign one person to be the Moon and hand them the ball. Stay standing up, as you’ll be circling the Earth.
- The rest of the people are the Earth, and they stand or sit right the middle (so they don’t get a flashlight in their eyes as the Moon orbits).
- Start with a new Moon. Shine the flashlight above the heads of the Earth. Move the Moon (ball) into position so that the ball blocks all the light from the flashlight. Ask the Earth kids how much light they can see on their side of the Moon (should be none). Which phase of the Moon is this?
- Now the Moon moves around to the opposite side of the Earth so that the Earth kids can see the entire half of the ball lit up by the flashlight. Ask the Earth kids how much light they can see on their side of the Moon (should be half the ball). Which phase of the Moon is this?
- Now find the positions for first quarter. Where does the Moon need to stand so that the Earth kids can see the first quarter Moon?
- Continue around in a complete circle and fill out the diagram. Color in the circles to indicate the dark half of the Moon. For example, the new Moon should be completely darkened.
- Now it’s time to investigate why Venus and Mercury have phases. Put the Sun in the center and assign a student to be Venus. Venus gets the ball.
- Venus should be walking slowly around the Sun. The Sun is going to have to rotate to always face Venus, since the Sun normally gives off light in every direction.
- The Earth kids need to move further out from the Sun than Venus, so they will be watching Venus orbit the Sun from a distance of a couple of feet.
- Earth kids: What do you notice about how the Sun lights up Venus from your point of view? Is there a time when you get to see Venus completely illuminated, and other times when it’s completely dark?
- Draw a diagram of what’s going on, labeling Venus’s full phase, new phase, half phases, crescent, and gibbous phases. Label the Sun, Earth, and all eight phases of Venus.
Reading
The Sun illuminates half of the Moon all the time. Imagine shining a flashlight on a beach ball. The half that faces the light is lit up. There’s no light on the far side, right? So for the Moon, which half is lit up depends on the rotation of the Moon. And which part of the illuminated side we can see depends on where we are when looking at the Moon. Sound complicated? This lab will straighten everything out so it makes sense.
One question you’ll hear is: Why don’t we have eclipses every month when there’s a new Moon? The next lesson is all about eclipses, but you can quickly answer their questions by reminding them that the Moon’s orbit around the Earth is not in the same plane as the Earth’s orbit around the Sun (called the ecliptic). It’s actually off by about 5o. In fact, only twice per month does the Moon pass through the ecliptic.
The lunar cycle is approximately 28 days. To be exact, it takes on average 29.53 days (29 days, 12 hours, 44 minutes) between two full moons. The average calendar month is 1/12 of a year, which is 30.44 days. Since the Moon’s phases repeat every 29.53 days, they don’t quite match up. That’s why on Moon phase calendars, you’ll see a skipped day to account for the mismatch.
A second full Moon in the same month is called a blue Moon. It’s also a blue Moon if it’s the third full Moon out of four in a three-month season, which happens once every two or three years.
The Moon isn’t the only object that has phases. Mercury and Venus undergo phases because they are closer to the Sun than the Earth. If we lived on Mars, then the Earth would also have phases.
Exercises
- Does the sun always light up half the Moon?
- How many phases does the Moon have?
- What is it called when the Moon appears to grow?
- What is it called when you see more light than dark on the Moon?
- How long does it take for a complete lunar cycle?
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Do you have thick or thin hair? Let’s find out using a laser to measure the width of your hair and a little knowledge about diffraction properties of light. (Since were using lasers, make sure you’re not pointing a laser at anyone, any animal, or at a reflective surface.)
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Light is also called “electromagnetic radiation”, and it can move through space as a wave, which makes it possible for light to interact in surprising ways through interference and diffraction. This is especially amazing to watch when we use a concentrated beam of light, like a laser.
If we shine a flashlight on the wall, you’ll see the flashlight doesn’t light up the wall evenly. In fact, you’ll probably see lots of light with a scattering of dark spots, showing some parts of the wall more illuminated than the rest. What happens if you shine a laser on the wall? You’ll see a single dot on the wall.
In this experiment, we used a laser to discover how interference and diffraction work. We can use diffraction to accurately measure very small objects, like the spacing between tracks on a CD, the size of bacteria, and also the thickness of human hair.
Here’s what you need:
- a strand of hair
- laser pointer
- tape
- calculator
- ruler
- paper
- clothespin
WARNING! The beam of laser pointers is so concentrated that it can cause real damage to your retina if you look into the beam either directly or by reflection from a shiny object. Do NOT shine them at others or yourself.
Download Student Worksheet & Exercises
- Tape the hair across the open end of the laser pointer (the side where the beam emits from)
- Measure 1 meter (3.28 feet) from the wall and put your laser right at the 1 meter mark.
- Clip the clothespin onto the laser so that it keeps the laser on.
- Where the mark shows up on the wall, tape a sheet of paper.
- Mark on the sheet of paper the distance between the first two black lines on either side of the center of the beam.
- Use your ruler to measure (in centimeters) to measure the distance between the two marks you made on the paper. Convert your number from centimeters to meters (For me, 8 cm = 0.08 meters.)
- Read the wavelength from your laser and write it down. It will be in “nm” for nanometers. My laser was 650 nm, which means 0.000 000 650 meters.
- Calculate the hair width by multiplying the laser wavelength by the distance to the wall (1 meter), and divide that number by the distance between the dark lines. Multiply your answer by 2 to get your final answer. Here’s the equation:
Hair width = [(Laser Wavelength) x (Distance to Wall)] / [ (Distance between dark lines) x 0.5 ]
In the video:
- wavelength was 650 nm = 0.000 000 650 meters
- distance from the wall was 1 meter
- the distance between the dark lines was 8 cm = 0.08 m
Using a calculator, this gives a hair width of 0.000 0162 5meters, or 16.25 micrometers (or 0.000 629 921 26 inches). Now you try!
What’s Going On?
The image here shows how two different waves of light interact with each other. When a single light wave hits a wall, it shows up as a bright spot (you wouldn’t see a “wave”, because we’re talking about light).
When both waves hit the wall, if they are “in phase”, they add together (called constructive interference), and you see an even brighter spot on the wall.
If the waves are “out of phase”, then they subtract from each other (called “destructive interference”) and you’d see a dark spot. In advanced labs, like in college, you’ll learn how to create a phase shift between two waves by adding extra travel length to one of the waves along its path.
So why are there dark lines along the light line when you shine your laser on the hair in this experiment? It has to do with something called “interference”.
One kind of interference happens when light goes through a small and narrow opening, called a slit. When light travels through a single slit, it can interfere with itself. This is called diffraction.
When light travels through one of two slits, it can interfere with light traveling through the other slit, a lot like how water ripples can interfere with each other as they travel over the surface of water.
If you’re wondering where the slit is in this experiment, you’re right! There’s no narrow opening that light it traveling through. in fact, light appears to be traveling around something, doesn’t it? Light from the laser must travel around the hair to get to the wall. The way that light does this has to do with Babinet’s Principle, which relates the opposite of a slit (a small object the size of a slit) to the slit itself.
It turns out amazingly enough that when light hits a small solid object, like a piece of hair, it creates the same interference pattern as if the hair were replaced with a hole of the same size. This idea is called Babinet’s Principle.
By measuring the diffraction pattern on the wall, we can measure the width of a small object that the light had to travel around by measuring the dark lanes in the spot on the wall. In our lab, the small object is a piece of your hair!
Questions to Ask:
- What would happen to the diffraction pattern if the hair width was smaller?
- Using this experiment, how can you tell if the hair is round or oval?
- If we redid these experiments with a different color laser instead of red, what changes would you have needed to make?
- How can you modify this experiment to measure the width of a track on a CD? Does the track width change as a function of location on the CD? If so, is it larger or smaller near the outside?
Exercises
- Which light source gave the most interesting results?
- What happens when you aim a laser beam through the diffraction grating?
- How is a CD different and the same as a diffraction grating?
- Why does the feather work?
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Many wonders are visible when flying over the Earth at night, especially if you are an astronaut on the International Space Station (ISS)! Passing below are white clouds, orange city lights, lightning flashes in thunderstorms, and dark blue seas. On the horizon is the golden haze of Earth’s thin atmosphere, frequently decorated by dancing auroras as the video progresses. The green parts of auroras typically remain below the space station, but the station flies right through the red and purple auroral peaks. You’ll also see solar panels of the ISS around the frame edges. The wave of approaching brightness at the end of each sequence is just the dawn of the sunlit half of Earth, a dawn that occurs every 90 minutes, as the ISS travels at 5 miles per second to keep from crashing into the earth.
Video Credit: Gateway to Astronaut Photography, NASA
Did you know that you can use a laser to see tiny paramecia in pond water? We’re going to build a simple laser microscope that will shine through a single drop of water and project shadows on a wall or ceiling for us to study.
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Here’s how it works: by shining a laser though a drop of water, we can see the shadows of objects inside the water. It’s like playing shadow puppets, only we’re using a highly concentrated laser beam instead of a flashlight.
If you’re wondering how a narrow laser beam spreads out to cover a wall, it has to do with the shape of the water droplet. Water has surface tension, which makes the water want to curl into a ball shape. But because water’s heavy, the ball stretches a little. This makes the water a tear-drop shape, which makes it act like a convex lens, which magnifies the light and spreads it out:
Here’s how to make your own laser microscope:
Materials:
- red or green laser (watch video for laser tips)
- large paperclip
- rubber band
- stack of books
- white wall
- pond water sample (or make your own from a cup of water with dead grass that’s been sitting for a week on the windowsill)
Download Student Worksheet & Exercises
Exercises
- Does this work with other clear liquids?
- What kind of lens occurs if you change the amount of surface tension by using soapy water instead?
- Does the temperature of the water matter? What about a piece of ice?
- Does this work with a flashlight instead of a laser?
- Do lasers hurt your eyes? How?
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Being able to predict tomorrow's weather is one of the most challenging and frequently requested bits of information to provide. Do you need a coat tomorrow? Will soccer practice be canceled? Will the crops freeze tonight?
Scientists use different instruments to record the current weather conditions, like temperature, barometric pressure, wind speed, humidity, etc. The real work comes in when they spend time looking over their data over days, months, even years and search for patterns.
But where does the weather station get its weather from?
One of the greatest leaps in meteorology was using numbers to predict the flow of the atmosphere. The math equations needed for these (using fluid dynamics and thermodynamics) are enough to make even a graduate student quiver with fear. Even today's most powerful computers cannot solve these complex equations! The best they can do is make a guess at the solution and then adjust it until it fits well enough in a given range. How do the computers know what to guess?
Several weather stations around the world work together to report the current weather every hour. These stations can be land-based, mounted on buoys in the ocean, or launched on radiosondes and report back to a home station as they rise through the different layers of the atmosphere. Pilots will also give weather reports en route to their destination, which get recorded and added to the database of weather knowledge.
We're going to build our own homemade weather station and start keeping track of weather right in your own home town. By keeping a written record (even if it's just pen marks on the wall), you'll be able to see how the weather changes and even predict what it will do, once you get the hang of the pattern in your local area. For example, if you live in Florida, what happens to the pressure before the daily afternoon thunderstorm? Or if you live in the deserts of Arizona, what does a sudden increase in humidity tell you?
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This is an introductory video that will get you started making your own weather station:
Once you have your weather station up and working, you can make another and send set it up at a friend's house or a distant relative. Ask them to read you the instruments when you call them so you can have more than one weather tracking station!
By understanding how the atmosphere moves and changes, scientists can guess on what it will do tomorrow based on what it's done in the past. Even with our massive super-computers today, people are still required to make certain calculations and decisions as to which set of math equations best fit (model) what the weather's currently doing. Maybe one day computers will be able to do this, but we're not there yet.
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One of the most remarkable images of our planet has always been how dynamic the atmosphere is a photo of the Earth taken from space usually shows swirling masses of white wispy clouds, circling and moving constantly. So what are these graceful puffs that can both frustrate astronomers and excite photographers simultaneously?
Clouds are frozen ice crystals or white liquid water that you can see with your eyes. Scientists who study clouds go into a field of science called nephology, which is a specialized area of meteorology. Clouds don’t have to be made up of water – they can be any visible puff and can have all three states of matter (solid, liquid, and gas) existing within the cloud formation. For example, Jupiter has two cloud decks: the upper are water clouds, and the lower deck are ammonia clouds.
We’re going to learn how to build a weather instrument that will record whether (weather?) the day was sunny or cloudy using a very sensitive piece of paper. Are you ready?
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Materials:
- Sun print paper or other paper sensitive to light
- Film canister or soup can
- Drill with drill bit
- Scissors
- Sunlight
The paper from a sun print kit has a very special coating that makes the paper react to light. Most sun print kits use set of light-sensitive chemicals such as potassium ferricyanide and ferric ammonium citrate to make a cyanotype solution. The paper changes color when exposed to UV light. In fact, you can try exposing the paper to different colors and see which changes the paper the most over a set amount of time!
The last step of this chemical process is to ‘set’ the reaction by washing it in plain water – this keeps the image on the paper so it doesn’t all disappear when you hang it on the wall. After the paper dries, the area exposed to UV light turns blue, and everything shaded turns white.
You can use sun print paper to test how well your sunblock works – just smear your favorite sunscreen over a sheet (or put a couple dabs of each kind) and see how well the paper stays protected: if it turns white, the light is getting through. If it stays blue, the sunscreen blocked the light!
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First invented in the 1600s, thermometers measure temperature using a sensor (the bulb tip) and a scale. Temperature is a way of talking about, measuring, and comparing the thermal energy of objects. We use three different kinds of scales to measure temperature. Fahrenheit, Celsius, and Kelvin. (The fourth, Rankine, which is the absolute scale for Fahrenheit, is the one you’ll learn about in college.)
Mr. Fahrenheit, way back when (18th century) created a scale using a mercury thermometer to measure temperature. He marked 0° as the temperature ice melts in a tub of salt. (Ice melts at lower temperatures when it sits in salt. This is why we salt our driveways to get rid of ice). To standardize the higher point of his scale, he used the body temperature of his wife, 96°.
As you can tell, this wasn’t the most precise or useful measuring device. I can just imagine Mr. Fahrenheit, “Hmmm, something cold…something cold. I got it! Ice in salt. Good, okay there’s zero, excellent. Now, for something hot. Ummm, my wife! She always feels warm. Perfect, 96°. ” I hope he never tried to make a thermometer when she had a fever.
Just kidding, I’m sure he was very precise and careful, but it does seem kind of weird. Over time, the scale was made more precise and today body temperature is usually around 98.6°F.
Later, (still 18th century) Mr. Celsius came along and created his scale. He decided that he was going to use water as his standard. He chose the temperature that water freezes at as his 0° mark. He chose the temperature that water boils at as his 100° mark. From there, he put in 100 evenly spaced lines and a thermometer was born.
Last but not least Mr. Kelvin came along and wanted to create another scale. He said, I want my zero to be ZERO! So he chose absolute zero to be the zero on his scale.
Absolute zero is the theoretical temperature where molecules and atoms stop moving. They do not vibrate, jiggle or anything at absolute zero. In Celsius, absolute zero is -273 ° C. In Fahrenheit, absolute zero is -459°F (or 0°R). It doesn’t get colder than that!
As you can see, creating the temperature scales was really rather arbitrary:
“I think 0° is when water freezes with salt.”
“I think it’s just when water freezes.”
“Oh, yea, well I think it’s when atoms stop!”
Many of our measuring systems started rather arbitrarily and then, due to standardization over time, became the systems we use today. So that’s how temperature is measured, but what is temperature measuring?
Temperature is measuring thermal energy which is how fast the molecules in something are vibrating and moving. The higher the temperature something has, the faster the molecules are moving. Water at 34°F has molecules moving much more slowly than water at 150°F. Temperature is really a molecular speedometer.
Let’s make a quick thermometer so you can see how a thermometer actually works:
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Materials:
- plastic bottle
- straw
- hot glue or clay
- water
- food coloring
- rubbing alcohol
- index card and pen
When something feels hot to you, the molecules in that something are moving very fast. When something feels cool to you, the molecules in that object aren’t moving quite so fast. Believe it or not, your body perceives how fast molecules are moving by how hot or cold something feels. Your body has a variety of antennae to detect energy. Your eyes perceive certain frequencies of electromagnetic waves as light. Your ears perceive certain frequencies of longitudinal waves as sound. Your skin, mouth and tongue can perceive thermal energy as hot or cold. What a magnificent energy sensing instrument you are!
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Hygrometers measure how much water is in the air, called humidity. If it's raining, it's 100% humidity. Deserts and arid climates have low humidity and dry skin. Humidity is very hard to measure accurately, but scientists have figured out ways to measure how much moisture is absorbed by measuring the change in temperature (as with a sling psychrometer), pressure, or change in electrical resistance (most common).
The dewpoint is the temperature when moist air hits the water vapor saturation point. If the temperature goes below this point, the water in the air will condense and you have fog. Pilots look for temperature and dewpoint in their weather reports to tell them if the airport is clear, or if it''s going to be 'socked in'. If the temperature stays above the dewpoint, then the airport will be clear enough to land by sight. However, if the temperature falls below the dewpoint, then they need to land by instruments, and this takes preparation ahead of time.
A sling psychrometer uses two thermometers (image above), side by side. By keeping one thermometer wet and the other dry, you can figure out the humidity using a humidity chart. Such as the one on page two of this document. The psychrometer works because it measures wet-bulb and dry-bulb temperatures by slinging the thermometers around your head. While this sounds like an odd thing to do, there's a little sock on the bottom end of one of the thermometers which gets dipped in water. When air flows over the wet sock, it measures the evaporation temperature, which is lower than the ambient temperature, measured by the dry thermometer.
Scientists use the difference between these two to figure out the relative humidity. For example, when there's no difference between the two, it's raining (which is 100% humidity). But when there's a 9oC temperature difference between wet and dry bulb, the relative humidity is 44%. If there's 18oC difference, then it's only 5% humidity.
You can even make your own by taping two identical thermometers to cardboard, leaving the ends exposed to the air. Wrap a wet piece of cloth or tissue around the end of one and use a fan to blow across both to see the temperature difference!
One of the most precise are chilled mirror dewpoint hygrometers, which uses a chilled mirror to detect condensation on the mirror's surface. The mirror's temperature is controlled to match the evaporation and condensation points of the water, and scientists use this temperature to figure out the humidity.
We're going to make a very simple hygrometer so you get the hand of how humidity can change daily. Be sure to check this instrument right before it rains. This is a good instrument to read once a day and log it in your weather data book.
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Materials:
- single hair
- index card
- tack
- cardboard
- tape
- scissors
- dime
This device works because human hair changes length with humidity, albeit small. We magnify this change by using a lever arm (the arrow and mark the different places on the cardboard to indicate levels of humidity. Does all hair behave the same way? Does it matter if you use curly or straight hair, or even the color of the hair? Does gray work better than blonde?
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Most weather stations have anemometers to measure wind speed or wind pressure. The kind of anemometer we’re going to make is the same one invented back in 1846 that measures wind speed. Most anemometers use three cups, which is not only more accurate but also responds to wind gusts more quickly than a four-cup model.
Some anemometers also have an aerovane attached, which enables scientists to get both speed and direction information. It looks like an airplane without wings – with a propeller at the front and a vane at the back.
Other amemometers don’t have any moving parts – instead they measure the resistance of a very short, thin piece of tungsten wire. (Resistance is how much a substance resists the flow of electrical current. Copper has a low electrical resistance, whereas rubber has a very high resistance.) Resistance changes with the material’s temperature, so the tungsten wire is heated and placed in the airflow. The wind flowing over the wire cools it down and increases the resistance of the wire, and scientists can figure out the wind speed.
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Scientists also use sonic anemometers, which use ultrasonic waves to detect wind speed. The great thing about sonic anemometers is that they can measure speed in all three directions, which is great for studying wind that is not all moving in the same direction (like gusts and hurricanes).
Sonic anemometers send a sound wave from one side to the other and measure the time it takes to travel. Which means that these can also be used as thermometers, as temperature will also change the speed of sound. Since there are no moving parts, you’ll find these types of anemometers in harsh conditions, like on a buoy or in the desert, where salt disintegrates and dust gets in the way of the cup-style anemometer. The big drawback to sonic anemometers is water (like dew or rain): if the transducers get wet, it changes the speed of sound and gives an error in the reading.
The quickest anemometer to make is to attach the end of a string (about 12″ long) to a ping pong ball. Suspend the string in the wind, like from a fan or hair dryer (use the ‘cool’ setting). Since the ball is so lightweight, it’s quite responsive to wind speed.
Add a protractor flipped upside down (so you can measure the angle of the string). Use the measurements below to figure out the wind speed. For example, mark the 90o angle with “0 mph”. This is your ping pong ball at rest in no wind. Use the numbers below to make the rest:
| Angle | Wind Speed |
| degrees | mph |
| 90 | 0 |
| 80 | 8 |
| 70 | 12 |
| 60 | 15 |
| 50 | 18 |
| 40 | 21 |
| 30 | 26 |
| 20 | 33 |
Now let’s make a four-cup anemometer. Here’s what you need to do:
Materials:
- four lightweight cups
- two sticks or popsicle sticks
- tape or hot glue
- tack or pin
- pencil with eraser on top
- block of foam (optional)
How steady was the wind that you measured? If you place your anemometer next to a door or a window, is there wind? How fast? Where could you place your anemometer so you can quickly read it each day?
By making two anemometers, one that you already know what the wind speed is, you can easily figure out how to calibrate the other. For example, how fast do the cups fly around when the ping pong ball anemometer indicates 12 mph? Can you see each cup, or are they a blur? You’ll get a feel for how to read the four-cup model by eye once you’ve had practice.
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A barometer uses either a gas (like air) or a liquid (like water or mercury) to measure pressure of the atmosphere. Scientists use barometers a lot when they predict the weather, because it’s usually a very accurate way to predict quick changes in the weather.
Barometers have been around for centuries – the first one was in the 1640s!
At any given momen, you can tell how high you are above sea level by measure the pressure of the air. If you measure the pressure at sea level using a barometer, and then go up a thousand feet in an airplane, it will always indicate exactly 3.6 kPa lower than it did at sea level.
Scientists measure pressure in “kPa” which stands for “kilo-Pascals”. The standard pressure is 101.3 kPa at sea level, and 97.7 kPa 1,000 feet above sea level. In fact, every thousand feet you go up, pressure decreases by 4%. In airplanes, pilots use this fact to tell how high they are. For 2,000 feet, the standard pressure will be 94.2 kPa. However, if you’re in a low front, the sea level pressure reading might be 99.8 kPa, but 1000 feet up it will always read 3.6 kPa lower, or 96.2 kPa.
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Materials:
- balloon
- straw or stick
- water glass or clean jam jar
- index card
- tape
At standard pressure, depending on the kind of barometer you have, you’ll find they all read one of these: 101.3 kPa; 760 mmHg (millimeters of mercury, or “torr”); 29.92 inHg (inches of mercury); 14.7 psi (pounds per square inch); 1013.25 millibars/hectopascal. They are all different unit systems that all say the same thing.
Just like you can have 1 dollar or four quarters or ten dimes or 20 nickels or a hundred pennies, it’s still the same thing.
Why does water boil differently at sea level than it does on a mountain top?
It takes longer to cook food at high altitude because water boils at a lower temperature. Water boils at 212oF at standard atmospheric pressure. But at elevations higher than 3,500 feet, the boiling point of water is decreased.
The boiling point is defined when the temperature of the vapor pressure is equal to the atmospheric pressure. Think of vapor pressure as the pressure made by the water molecules hitting the inside of the container above the liquid level. But since the saucepan of water is not sealed, but rather open to the atmosphere, the vapor simply expands to the atmosphere and equals out. Since the pressure is lower on a mountaintop than at sea level, this pressure is lower, and hence the boiling point is lowered as well.
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Also known as an udometer or pluviometer or ombrometer, or just plan old ‘rain cup’, this device will let you know how much water came down from the skies. Folks in India used bowls to record rainfall and used to estimate how many crops they would grow and thus how much tax to collect!
These devices reports in “millimeters of rain” or “”centimeters of rain” or even inches of rain”. Sometimes a weather station will collect the rain and send in a sample for testing levels of pollutants.
While collecting rain may seem simple and straightforward, it does have its challenges! Imagine trying to collect rainfall in high wind areas, like during a hurricane. There are other problems, like trying to detect tiny amounts of rainfall, which either stick to the side of the container or evaporate before they can be read on the instrument. And what happens if it rains and then the temperature drops below freezing, before you’ve had a chance to read your gauge? Rain gauges can also get clogged by snow, leaves, and bugs, not to mention used as a water source for birds.
So what’s a scientist to do?
Press onward, like all great scientists! And invent a type of rain gauge that will work for your area. We’re going to make a standard cylinder-type rain gauge, but I am sure you can figure out how to modify it into a weighing precipitation type (where you weigh the amount in the bottle instead of reading a scale on the side), or a tipping bucket type (where a funnel channels the rain to a see-saw that tips when it gets full with a set amount of water) , or even a buried-pit bucket (to keep the animals out).
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Materials:
- two water bottles
- scissors
- rainy day (or use water)
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How many of these items do you already have? We’ve tried to keep it simple for you by making the majority of the items things most people have within reach (both physically and budget-wise).
This particular shopping list has many different projects on it, so we’ve broken the list into sections based on the projects. For example, the roller coaster activities are all in one area, the weather station in another, etc. You might want to view the videos before gathering your supplies.
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Materials
Materials for Sonic Vibrations Experiments
- 3 popsicle sticks (tongue depressor size)
- 2 index cards
- Scissors, tape, hot glue gun
- 2 film canisters (or plastic snap-lid M&M containers)
- Straw
- Three 7-9” balloons
- 2 water balloons
- 3’ string
- Rubber bands (at least two are ¼” thick)
- Disposable cup (plastic, foam, or paper)
- Hexnut (1/4” or smaller)
- Razor or drill to make holes in the film canister
- Scissors, tape
Weather Station Project
- 2 popsicle sticks
- 1 long strand of hair
- 1 index card
- 12” piece of cardboard (scraps are great)
- 4 foam cups
- 2 popsicle sticks
- 1 pencil with built-in eraser on top
- 2 tacks
- 1 nickel
- Scissors
- Tape
- 7-9” balloon
- Water glass
- Straw or wooden skewer
- Empty water bottle
- Funnel
- Rubbing alcohol
- Clay
- Straw
- Food coloring
- Optional: Sunprint Paper and soup can
Magic Tricks
- Dollar bill
- 2 small paperclips
- 6’ of rope
- 1 rubber band
- 1 toilet paper tube
- 1 egg (hard boiled) OR ball that sits on the end of the toilet paper tube without falling in
- Aluminum pie plate or plastic dish (something not breakable)
- Broom handle or ruler
- Shoe with laces
- Four bracelets (optional)
Materials for Roller Coasters Experiments
- ¾” foam pipe insulation
- Masking tape
- A handful of marbles
- Chairs and tables
Materials for Clothespin Catapult Project
- Popsicle sticks
- Plastic spoon
- 3 rubber bands
- Wood clothespin
- Straw
- Wood dowel that fits inside the straw
- Scissors
- Hot glue gun
Materials for Mousetrap RaceCar
- Mousetrap (NOT a rat trap)
- Foam block or piece of cardboard
- Four old CDs
- Thin string or fishing line
- Wood dowel or long, straight piece from a wire coat hanger (use pliers to straighten it)
- Straw
- Two wood skewers (that fit inside straw)
- Hot glue gun
- Duct tape
- Scissors
- Four caps to water bottles
- Drill
- Razor with adult help
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Objective You will learn about force, acceleration, velocity, and what scientist really mean when they say, “Try it again…and again…and again… until you get the result you want.” This lab uses the Iteration Technique to solving a problem, which is different than the Scientific Method, and actually much more widely used by engineers in the science field.
About the Experiment This lab is an excellent opportunity for kids to practice their resilience, because we guarantee this experiment will not work the first several times they try it. While you can certainly help the kids out, it’s important that you help them figure it out on their own. You can do this by asking questions instead of rushing in to solve their problems. For instance, when the marble flies off the track, you can step back and say:
“Hmmm… did the marble go to fast or too slow?”
“Where did it fly off?”
“Wow – I’ll bet you didn’t expect that to happen. Now what are you going to try?”
Become their biggest fan by cheering them on, encouraging them to make mistakes, and try something new (even if they aren’t sure if it will work out). One of the greatest gifts you can give your child is the expectation of their success.
The How and Why To make the roller coasters, you’ll need foam pipe insulation, which is sold by the six-foot increments at the hardware store. You’ll be slicing them in half lengthwise, so each piece makes twelve feet of track. It comes in all sizes, so bring your marbles when you select the size. The ¾” size fits most marbles, but if you’re using ball bearings or shooter marbles, try those out at the store. (At the very least you’ll get smiles and interest from the hardware store sales people.) Cut most of the track lengthwise (the hard way) with scissors. You’ll find it is already sliced on one side, so this makes your task easier. Leave a few pieces uncut to become “tunnels” for later roller coasters.
The next step is to join your track together before adding all the features like loops and curves. Join two tracks together in butt-joint fashion and press a piece of masking tape lengthwise along both the inside and the underside of the track. A third piece of tape should go around the entire joint circumferentially. Make this connection as smooth as possible, as your high-speed marble roller coaster will tend to fly off the track at the slightest bump.
Loops Swing the track around in a complete circle and attach the outside of the track to chairs, table legs, and hard floors with tape to secure in place. Loops take a bit of speed to make it through, so have your partner hold it while you test it out before taping. Start with smaller loops and increase in size to match your entrance velocity into the loop. Loops can be used to slow a marble down if speed is a problem.
Camel-Backs Make a hill out of track in an upside-down U-shape. Good for show, especially if you get the hill height just right so the marble comes off the track slightly, then back on without missing a beat.
Whirly-Birds Take a loop and make it horizontal. Great around poles and posts, but just keep the bank angle steep enough and the marble speed fast enough so it doesn’t fly off track.
Corkscrew Start with a basic loop, then spread apart the entrance and exit points. The further apart they get, the more fun it becomes. Corkscrews usually require more speed than loops of the same size.
Jump Track A major show-off feature that requires very rigid entrance and exit points on the track. Use a lot of tape and incline the entrance (end of the track) slightly while declining the exit (beginning of new track piece).
Pretzel The cream of the crop in maneuvers! Make a very loose knot that resembles a pretzel. Bank angles and speed are the most critical, with rigid track positioning a close second. If you’re having trouble, make the pretzel smaller and try again. You can bank the track at any angle because the foam is so soft. Use lots of tape and a firm surface (bookcases, chairs, etc).
Troubleshooting Marbles will fly everywhere, so make sure you have a lot of extras! If your marble is not following your track, look very carefully for the point of departure – where it flies off.
- Does the track change position with the weight of the marble, making it fly off course? Make the track more rigid by taping it to a surface.
- Is the marble jumping over the track wall? Increase your bank angle (the amount of twist the track makes along its length).
- Does your marble just fall out of the loop? Increase your marble speed by starting at a higher position. When all else fails and your marble still won’t stay on the track, make it a tunnel section by taping another piece on top the main track. Spiral-wrap the tape along the length of both pieces to secure them together.
Why does the marble stick to the track? The faster the marble travels in a loop, the more it sticks to the track. This is the same pancake feeling you get when your body gets pulled into a tight turn (whether in a car or on a roller coaster). The faster and tighter the turn, the more the “pancake feeling”. That pancake thing is called acceleration. You’re feeling a pull away from the center of the loop, which will vary depending on how fast you are going, called centrifugal force.
That’s usually enough for kids. But if you really want to be thoroughly confused, keep reading about how centripetal and centrifugal forces are NOT the same thing:
What about centripetal force? Ah, yes… these two words constantly throw college students into a frenzy, partially because there is no clear definition in most textbooks. As I best understand it, centripetal (translation = “center-seeking”) force is the force needed to keep an object following a curved path. Remember how objects will travel in a straight line unless they bump into something or have another force acting on it (gravity, drag force, etc.)? Well, when you swing a bucket of water around, the force to keep the bucket of water swinging in a curved arc is the centripetal force, which can be felt in the tension experienced by the handle (or your arm, in our case). Swinging an object around on a string will cause the rope to undergo tension (centripetal force), and if your rope isn’t strong enough, it will snap and break, sending the mass flying off in a tangent (straight) line until gravity and drag force pull the object to a stop. This force is proportional to the square of the speed… the faster you swing the object, the higher the force.
Centrifugal (translation = “center-fleeing”) force has two different definitions, which also causes confusion. The inertial centrifugal force is the most widely referred to, and is purely mathematical, having to do with calculating kinetic forces using reference frames, and is used with Newton’s laws of motion. It’s often referred to as the ‘fictitious force’.
The other kind, reactive centrifugal force, happens when objects move in a curved path. This force is actually the same magnitude as centripetal force, but in the opposite direction, and you can think of it as the reaction force to the centripetal force. Think of how you stand on the Earth… your weight pushes down on the Earth, and a reaction force (called the “normal” force) pushes up in reaction to your weight, keeping you from falling to the center of the Earth. A centrifugal governor (spinning masses that regulate the speed of an engine) and a centrifugal clutch (spinning disk with two masses separated by a spring inside) are examples of this kind of force in action.
One more example: Imagine driving a car along a banked turn. The road exerts a centripetal force on the car, keeping the car moving in a curved path (the “banked” turn). If you neglected to buckle your seat belt and the seats have a fresh coat of Armor-All (making them slippery), then as the car turns along the banked curve, you get “shoved” toward the door. But who pushed you? No one – your body wanted to continue in a straight line but the car keeps moving in your path, turning your body in a curve. The push of your weight on the door is the reactive centrifugal force, and the car pushing on you is the centripetal force.
What about the fictitious (inertial) centrifugal force? Well, if you imagine being inside the car as it is banking with the windows blacked out, you suddenly feel a magical ‘push’ toward the door away from the center of the bend. This “push” is the fictitious force invoked because the car’s motion and acceleration is hidden from you (the observer) in the reference frame moving within the car.
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Objective This noisy lab lets you experiment with the idea that sound is a vibration. By making over a dozen different noisemakers, you can explore how to change the sound speed and use everyday materials to annoy your parents.
About the Experiments Instead of starting with an explanation of how sound works, mystify your kids with it instead by picking one of the experiments that you know your kids will like. After they’ve build the project (you might want ear muffs for this lab), you can start asking them how they think it works. Give them the opportunity to figure it out by changing different things on their noisemaker (stretch the rubber band, increase the tube length, etc) to allow them a chance to hone their skills at figuring things out.
The How and Why Explanation Sound is everywhere. It can travel through solids, liquids, and gases, but it does so at different speeds. It can rustle through trees at 770 MPH (miles per hour), echo through the ocean at 3,270 MPH, and resonate through solid rock at 8,600 MPH. Sound is made by things vibrating back and forth, whether it’s a guitar string, drum head, or clarinet. The back and forth motion of an object (like the drum head) creates a sound wave in the air that looks a lot like a ripple in a pond after you throw a rock in. It radiates outward, vibrating it’s neighboring air molecules until they are moving around, too. This chain reaction keeps happening until it reaches your ears, where your “sound detectors” pick up the vibration and works with your brain to turn it into sound.
Your voice is a vibration, and you can feel it when you place a hand on your throat when you speak. As long as there are molecules around, sound will be traveling though them by smacking into each other. That’s why if you put an alarm clock inside a glass jar and remove the air, there’s no sound from the clock. There’s nothing to transfer the vibrational energy to – nothing to smack into to transfer the sound. It’s like trying to grab hold of fog – there’s nothing to hold on to.
Sound can change according to the speed at which it travels. Another word for sound speed is pitch. When the sound speed slows, the pitch lowers. With clarinet reeds, it’s high. Guitar strings can do both, as they are adjustable. If you look carefully, you can actually see the low pitch strings vibrate back and forth, but the high pitch strings move so quickly it’s hard to see. But you can detect the effects of both with your ears.
The range of your ears is about 20 – 20,000 Hz (cycles per second). Bats and dogs can hear a lot higher than we can. The image (right) is a real picture of an aircraft as it breaks the sound barrier – meaning that the aircraft is passing the speed that sounds travels at (about 700 mph). The white cloud you see in the photo is related to the shock waves that are forming around the craft as it moves into supersonic speeds. You can think of a shock wave as big pressure front, which creates clouds. In this photo, the pressure from the shock waves is condensing the water vapor in the air.
There are lots of things on earth that break the sound barrier – bullets and bullwhips, for example. The loud crack from a whip is the tip zipping faster than the speed of sound. Your air horn is a loud example of how sound waves travel through the air.
Questions to Ask When you’ve worked through most of the experiments ask your kids these questions and see how they do:
- Sound travels fastest in (a) air (b) the ocean (c) rock (d) outer space
- The hornet works because (a) the rubber band vibrates when the wind flies over it (b) you’ve trapped a real wasp in there (c) the string vibrates when you twirl it around (d) the card vibrates with the wind
- An old-fashioned telephone made from cups and string work great because (a) no batteries are required (b) the cup vibrates (c) the string vibrates (d) your voice vibrates (e) all of the above
- Knowing what you do know about sound and cups, which way do you think you would hold a cup up to your ear (open end or closed end?) to hear the conversation on the other side of a door?
- When you replaced the string with a slinky, why can’t you talk or hear voices through it anymore? What can you hear instead?
- What would you use to completely block out the sound of an alarm clock?
- Does the pitch increase or decrease when you fill a glass bottle while tapping the side with a fork?
- List out the different kinds of strings tested with the String Test, and number them in order of best to worst.
Did you know you can create a compound microscope and a refractor telescope using the same materials? It’s all in how you use them to bend the light. These two experiments cover the fundamental basics of how two double-convex lenses can be used to make objects appear larger when right up close or farther away.
Things like lenses and mirrors can bend and bounce light to make interesting things, like compound microscopes and reflector telescopes. Telescopes magnify the appearance of some distant objects in the sky, including the moon and the planets. The number of stars that can be seen through telescopes is dramatically greater than can be seen by the unaided eye.
Materials
- A window
- Dollar bill
- Penny
- Two hand-held magnifying lenses
- Ruler
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Download Student Worksheet & Exercises
- Place a penny on the table.
- Hold one magnifier above the penny and look through it.
- Bring the second magnifying lens above the first so now you’re looking through both. Move the second lens closer and/or further from the penny until the penny comes into sharp focus. You’ve just made a compound microscope.
- Who’s inside the building on an older penny?
- Try finding the spider/owl on the dollar bill. (Hint: It’s in a corner next to the “1”.)
- Keeping the distance between the magnifiers about the same, slowly lift up the magnifiers until you’re now looking through both to a window.
- Adjust the distance until your image comes into sharp (and upside-down) focus. You’ve just made a refractor telescope, just like Galileo used 400 years ago.
- Find eight different items to look at through your magnifiers. Make four of them up-close so you use the magnifiers as a microscope, and four of them far-away objects so you use the magnifiers like a telescope. Complete the data table.
What’s Going On?
What I like best about this activity is how easily we can break down the basic ideas of something that seems much more complex and intimidating, like a telescope or microscope, in a way that kids really understand.
When a beam of light hits a different substance (like a window pane or a lens), the speed at which the light travels changes. (Sound waves do this, too!) In some cases, this change turns into a change in the direction of the beam.
For example, if you stick a pencil is a glass of water and look through the side of the glass, you’ll notice that the pencil appears shifted. The speed of light is slower in the water (140,000 miles per second) than in the air (186,282 miles per second). This is called optical density, and the result is bent light beams and broken pencils.
You’ll notice that the pencil doesn’t always appear broken. Depending on where your eyeballs are, you can see an intact or broken pencil. When light enters a new substance (like going from air to water) perpendicular to the surface (looking straight on), refractions do not occur.
However, if you look at the glass at an angle, then depending on your sight angle, you’ll see a different amount of shift in the pencil. Where do you need to look to see the greatest shift in the two halves of the pencil?
Why does the pencil appear bent? Is it always bent? Does the temperature of the water affect how bent the pencil looks? What if you put two pencils in there?
Depending on if the light is going from a lighter to an optically denser material (or vice versa), it will bend different amounts. Glass is optically denser than water, which is denser than air.
Not only can you change the shape of objects by bending light (broken pencil or whole?), but you can also change the size. Magnifying lenses, telescopes, and microscopes use this idea to make objects appear different sizes.
Exercises
- Can light change speeds?
- Can you see ALL light with your eyes?
- Give three examples of a light source.
- What’s the difference between a microscope and a telescope?
- Why is the telescope image upside-down?
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If you’ve never made a paperclips jump together and link up by themselves, turned water into ink, or made metal rings pass through solid rope, you’re missing out. Big time. We’re going to show you our set of incredible magic-show-style tricks that will make you truly amazing.
But, there is something you should know about magic…
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Magic is not something you do, it’s something you perform. Any one of the following activities can become part of a first-rate magic show, or just a way to entertain your brain while waiting for the bus. It’s all a matter of how you deliver it.
Just like reading words is not singing, pulling a rabbit out of your hand is not magic. You need to pack as much ‘show’ into your act as you work to create the illusion and make it as believable as you can. This is called your ‘performance’, and you’ll be spending most of your time with this step… and that’s not the step we’re going to be doing here!
In this set of experiments, we’re going to show you several science experiments and a few hand trick secrets that you can develop into a magic show. You’ll need to figure out the ‘story’ to use – what you’re going to say to the audience and how you’re going to say it. Practice your presentation over and over, in front of the dog, mirror, friends, or team of stuffed animals until it’s smooth enough so you’re comfortable with doing it.
Most experiments require nothing more than a few household items. You’ll find materials listed separately for each magic trick. Before we start, though, there are two things I really want you to remember, now that you’re entering into the Magician’s World:
1. Never repeat a magic trick. Ever. Period.
2. Never give away your secret. Never, ever, ever in a million years.
If you find you’re being hounded by the audience to give it away, shrug and turn away. Don’t cave in, don’t give in. Keep your mouth shut and smile. (That alone will drive them nuts, which can be fun to watch, too.) Just smile and move onto something else. Another magic trick, perhaps?
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This trick is one of my favorites, because it's super-easy and quick... you'll have a hard time describing to yourself how it even happened. Most scientists can't explain it either. Are you ready?
Materials: dollar bill, two paperclips, and a rubber band.
Here's what you do:
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This particular trick kept me tied up for hours as a kid. I was so determined to figure this out that I eventually had a rope-impression rubbed into my skin when I finally did slide out. I’ll bet it doesn’t take you nearly as long, and you can substitute bracelets for the rope to make it more comfortable as you work. You need two kids for this trick to work. And a camera to capture the moment.
Materials: 6 feet of rope, two kids, and 4 bracelets (optional)
Here’s what you do:
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You might be curious about how to observe the sun safely without losing your eyeballs. There are many different ways to observe the sun without damaging your eyesight. In fact, the quickest and simplest way to do this is to build a super-easy pinhole camera that projects an image of the sun onto an index card for you to view.
CAUTION: DO NOT LOOK AT THE SUN THROUGH ANYTHING WITH LENSES!!
This simple activity requires only these materials:
- tack
- 2 index cards (any size)
- sunlight
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Here’s what you do:
Download Student Worksheet & Exercises
With your tack, make a small hole in the center of one of the cards. Stack one card about 12″ above the over and go out into the sun. Adjust the spacing between the cards so a sharp image of the sun is projected onto the lower paper. The sun will be about the size of a pea.
You can experiment with the size of the hole you use to project your image. What happens if your hole is really big? Too small? What if you bend the lower card while viewing? What if you punch two holes? Or three?
Exercises
- How many longitude degrees per day does the sunspot move?
- Do all sunspots move at the same rate?
- Did some of the sunspots change size or shape, appear or disappear?
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Objective You will learn about light waves and optics in this Laser Lab. Kids will play with their lasers and see what happens when they shine it on and through different objects.
Laser Safety Before we start our laser experiments, you’ll need eye protection – tinted UV ski goggles are great to use, as are large-framed sunglasses, but understand that these methods of eye protection will not protect your eyes from a direct beam. They are intended as a general safety precaution against laser beam scatter. (If you’re using a Class I or II laser, you don’t need to wear the goggles – but it is a good habit to get the kids into, so it’s up to you.)
About the Experiment This lab is an excellent opportunity for kids to practice asking better questions. Don’t worry too much about academics at this point – just give them a box of materials and let them figure these things out on their own. One of the neat things you can do is ask the kids some questions about what they are doing.
For example, when they shine their laser on a window, you’ll see part of the beam pass through while another part gets reflected back… now why is that? And why does the CD produce so many different reflections? Sometimes these reflections are hard to find actually seeing the beam itself. While red lasers are impossible to see with the naked eye, you can make your beam visible by doing your experiments in a steamy dark bathroom (after a hot shower).
The How and Why The word “LASER” stands for Light Amplification by Stimulated Emission of Radiation. A laser is an optical light source that emits a concentrated beam of photons. Lasers are usually monochromatic – the light that shoots out is usually one wavelength and color, and is in a narrow beam.
By contrast, light from a regular incandescent light bulb covers the entire spectrum as well as scatters all over the room. (Which is good, because could you light up a room with a narrow beam of light?)
There are about a hundred different types of atoms in the entire universe, and they are always vibrating, moving, and rotating. When you add energy to an atom, it vibrates faster and moves around a lot more. When the atoms relax back down to their “normal” state, they emit a photon (a light particle). A laser controls the way energized atoms release photons.
Imagine kids zooming all over the playground, a mixture of joy and chaos. Light from an incandescent light bulb works the same way – the bulb emits high energy photons that bounce all over the place. Can you round up the kids and get them to jumping in unison? Sure you can – just hit the play button on a song, and they’ll be clapping and stamping together. You can do the same with light – when you focus the energy into a narrow beam, it’s much more powerful than having it scattered all over the place. That’s just what a laser is – a high-energy, highly-focused beam of light.
Questions to Ask When you’ve worked through most of the experiments ask your kids these questions and see how they do:
- What does LASER stand for?
- How is a laser different from an incandescent bulb?
- What are two things that can split a laser beam?
- How do you make a laser beam visible?
- What’s the secret behind the laser light show?
- How do lasers damage things?
How many of these items do you already have? We’ve tried to keep it simple for you by making the majority of the items things most people have within reach (both physically and budget-wise).
You do not need to do ALL the experiments – just pick the ones you want to do! Look over the experiments and note which items are needed, and off you go!
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NOTE: Radio Shack part numbers have been replaced. Click here for full chart.
Materials
Materials for the Laser Light Show
- Red laser pointer
- Old CD you can scratch
- 5-6 small mirrors (like mosaic mirrors from a craft store)
- Ice cube
- Window
- Feather
- 3 large paper clips
- 10 brass fasteners
- Index card
- Cardboard
- Rubber band or zip tie
- Scissors
- Tape
- Two 3V DC motors
- Two AA battery packs
- Four AA batteries
- Three alligator wires
- Optional: plastic gem pieces
Materials for the Flashlight-Laser Tag, Laser Burglar Alarm, Door Alarm
- Red laser pointer (NOT GREEN!)
- 2 AA batteries
- Old pair of headphones (you need the plug section)
- Computer OR laptop OR portable amplifier
- CdS Cell
- One AA battery holder
- PNP Transistor 2N3906 or 2N4403
- NPN Transistor 2N3904 or 2N222A
- LED
- 4.7k-ohm resistor
- Soldering equipment or breadboard
- Optional: NC (normally-closed) switch
Materials for Crystal Radio Project: (This is a battery-free radio!)
- Toilet paper tube
- Magnet wire
- Germanium diode: 1N34A
- 4.7k-ohm resistor
- Alligator clip test leads
- 100’ stranded insulated wire (for the antenna)
- Scrap of cardboard
- Brass fasteners (3-4)
- Telephone handset or get a crystal earphone
Where’s the pressure difference in this trick?
At the opening of the glass. The water inside the glass weighs a pound at best, and, depending on the size of the opening of the glass, the air pressure is exerting 15-30 pounds upward on the bottom of the card. Guess who wins? Tip, when you get good at this experiment, try doing it over a friend’s head!
Materials: a glass, and an index card large enough to completely cover the mouth of the glass.
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Fill a glass one-third with water. Cover the mouth with an index card and over a sink invert the glass while holding the card in place. Remove your hand from the card. Voila! Because atmospheric air pressure is pushing on all sides of both the glass and the card, the card defies gravity and “sticks” to the bottom of the glass. Recall that higher pressure pushes and when you have a difference in pressure, things move. This same pressure difference causes storms, winds, and the index card to stay in place.
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This catapult requires a little more time, materials, and effort than the Fast Catapult, but it's totally worth it. This device is what most folks think of when you say 'catapult'. I've shown you how to make a small model - how large can you make yours?
This project builds on the ideas from Unit 5: Lesson 2: Kinetic Energy.
Materials:
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Try different ball weights (ping pong, foil crumpled into a ball, whiffle balls, marshmallows, etc) and chart out the results: make a data table that shows what ball you tried and how far it went. You can also use a stopwatch to time how long your ball was in the air.
You can also graph your results: make a chart where you plot each data point on a graph that has distance on the vertical axis and time on the horizontal axis.
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This project builds on the ideas from Unit 5: Lesson 2: Kinetic Energy.
Materials:
- plastic spoon
- 14 popsicle sticks
- 3 rubber bands
- wooden clothespin
- straw
- wood skewer or dowel
- scissors
- hot glue gun
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Try different ball weights (ping pong, foil crumpled into a ball, whiffle balls, marshmallows, etc) and chart out the results: make a data table that shows what ball you tried and how far it went. You can also use a stopwatch to time how long your ball was in the air.
You can also graph your results: make a chart where you plot each data point on a graph that has distance on the vertical axis and time on the horizontal axis.
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A super-fast, super-cool car that uses the pent-up energy inside a mouse trap spring to propel a homemade car forward. While normally this is reserved for high school physics classes, it really is a fun and inexpensive experiment to do with kids of all ages.
This is a great demonstration of how energy changes form. At first, the energy was stored in the spring of the mousetrap as elastic potential energy, but after the trap is triggered, the energy is transformed into kinetic energy as rotation of the wheels.
Remember with the First Law of Thermodynamics: energy can’t be created or destroyed, but it CAN change forms. And in this case, it goes from elastic potential energy to kinetic energy.
There’s enough variation in design to really see the difference in the performance of your vehicle. If you change the size of the wheels for example, you’ll really see a difference in how far it travels. If you change the size of the wheel axle, your speed is going to change. If you alter the size of the lever arm, both your speed and distance will change. It's fun to play with the different variables to find the best vehicle you can build with your materials!
Here's what you need to do this project:
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Materials:
Since the directions for this project are complex, it’s really best to watch the instructions on the video. Here are the highlights:
1. Tape the dowel to the outside of the wire on the mousetrap car (see image below). When the mousetrap spans closed, the dowel whips through the air along with it in an arc.
2. Attach a length of fishing line to the other end of the dowel. Don’t cut the fishing line yet.
3. Attach one straw near each end of a block of foam using hot glue.
4. Insert a skewer into each straw. Insert a wheel onto each end of the skewer. This is your wheel-axel assembly.
5. The wheels on one side should be close to the straw, the wheels on the other end should have a 1/2” gap.
6. Thread the end of the fishing line around the wheels with the gap as shown in the video.
7. Load the mousetrap car by spinning the back wheels as you set the trap.
8. Trigger the mousetrap with a pen (never use your fingers!). The dowel pulls the fishing line, unrolling it from the axel and spinning the wheels as it opens.
Energy has a number of different forms; kinetic, potential, thermal, chemical, electrical, electrochemical, electromagnetic, sound and nuclear. All of which measure the ability of an object or system to do work on another object or system.
In the physics books, energy is the ability to do work. Work is the exertion of force over a distance. A force is a push or a pull.
So, work is when something gets pushed or pulled over a distance against a force. Mathematically:
Work = Force x Distance or W = F d
Let me give you a few examples: If I was to lift an apple up a flight of stairs, I would be doing work. I would be moving the apple against the force of gravity over a distance. However, if I were to push against a wall with all my might, and if the wall never moved, I would be doing no work because the wall never moved. (There was a force, but no distance.)
Another way to look at this, is to say that work is done if energy is changed. By pushing on the non-moving wall, no energy is changed in the wall. If I lift the apple up a flight of stairs however, the apple now has more potential energy then it had when it started. The apple’s energy has changed, so work has been done.
All the different forms of energy can be broken down into two categories: potential and kinetic energy.
My students have nicknamed potential energy the “could” energy. The battery “could” power the flashlight. The light “could” turn on. I “could” make a sound. That ball “could” fall off the wall. That candy bar “could” give me energy.
Potential energy is the energy that something has that can be released. For example, the battery has the potential energy to light the bulb of the flashlight if the flashlight is turned on and the energy is released from the battery. Your legs have the potential energy to make you hop up and down if you want to release that energy (like you do whenever it’s time to do science!). The fuel in a gas tank has the potential energy to make the car move.
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This is a great demonstration of how energy changes form. At first, the energy was stored in the spring of the mousetrap as elastic potential energy, but after the trap is triggered, the energy is transformed into kinetic energy as rotation of the wheels.
Remember with the First Law of Thermodynamics: energy can’t be created or destroyed, but it CAN change forms. And in this case, it goes from elastic potential energy to kinetic energy.
There’s enough variation in design to really see the difference in the performance of your vehicle. If you change the size of the wheels for example, you’ll really see a difference in how far it travels. If you change the size of the wheel axle, your speed is going to change. If you alter the size of the lever arm, both your speed and distance will change. It's fun to play with the different variables to find the best vehicle you can build with your materials!
Here's what you need to do this project:
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Materials:
- Mousetrap (NOT a rat trap)
- Foam block or piece of cardboard
- Four old CDs
- Thin string or fishing line
- Wood dowel or long, straight piece from a wire coat hanger (use pliers to straighten it)
- Straw
- Two wood skewers (that fit inside straw)
- Hot glue gun
- Duct tape
- Scissors
- Four caps to water bottles
- Drill
- Razor with adult help
Since the directions for this project are complex, it’s really best to watch the instructions on the video. Here are the highlights:
1. Tape the dowel to the outside of the wire on the mousetrap car (see image below). When the mousetrap spans closed, the dowel whips through the air along with it in an arc.
2. Attach a length of fishing line to the other end of the dowel. Don’t cut the fishing line yet.
3. Attach one straw near each end of a block of foam using hot glue.
4. Insert a skewer into each straw. Insert a wheel onto each end of the skewer. This is your wheel-axel assembly.
5. The wheels on one side should be close to the straw, the wheels on the other end should have a 1/2” gap.
6. Thread the end of the fishing line around the wheels with the gap as shown in the video.
7. Load the mousetrap car by spinning the back wheels as you set the trap.
8. Trigger the mousetrap with a pen (never use your fingers!). The dowel pulls the fishing line, unrolling it from the axel and spinning the wheels as it opens.
What’s Going On?
Energy has a number of different forms; kinetic, potential, thermal, chemical, electrical, electrochemical, electromagnetic, sound and nuclear. All of which measure the ability of an object or system to do work on another object or system.
In the physics books, energy is the ability to do work. Work is the exertion of force over a distance. A force is a push or a pull.
So, work is when something gets pushed or pulled over a distance against a force. Mathematically:
Work = Force x Distance or W = F d
Let me give you a few examples: If I was to lift an apple up a flight of stairs, I would be doing work. I would be moving the apple against the force of gravity over a distance. However, if I were to push against a wall with all my might, and if the wall never moved, I would be doing no work because the wall never moved. (There was a force, but no distance.)
Another way to look at this, is to say that work is done if energy is changed. By pushing on the non-moving wall, no energy is changed in the wall. If I lift the apple up a flight of stairs however, the apple now has more potential energy then it had when it started. The apple’s energy has changed, so work has been done.
All the different forms of energy can be broken down into two categories: potential and kinetic energy.
My students have nicknamed potential energy the “could” energy. The battery “could” power the flashlight. The light “could” turn on. I “could” make a sound. That ball “could” fall off the wall. That candy bar “could” give me energy.
Potential energy is the energy that something has that can be released. For example, the battery has the potential energy to light the bulb of the flashlight if the flashlight is turned on and the energy is released from the battery. Your legs have the potential energy to make you hop up and down if you want to release that energy (like you do whenever it’s time to do science!). The fuel in a gas tank has the potential energy to make the car move.
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Did you know that the word LASER stands for Light Amplification by Stimulated Emission of Radiation? And that a MASER is a laser beam with wavelengths in the microwave part of the spectrum? Most lasers fire a monochromatic (one color) narrow, focused beam of light, but more complex lasers emit a broad range of wavelengths at the same time.
In 1917, Einstein figured out the basic principles for the LASER and MASER by building on Max Planck’s work on light. It wasn’t until 1960, though when the first laser actually emitted light at Hughes Research Lab. Today, there are several different kinds of lasers, including gas lasers, chemical lasers, semiconductor lasers, and solid state lasers. One of the most powerful lasers ever conceived are gamma ray lasers (which can replace hundreds of lasers with only one) and the space-based x-ray lasers (which use the energy from a nuclear explosion) – neither of these have been built yet!
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Gas lasers pump different types of gases to get different laser colors such as the red HeNe (Helium-Neon laser), the high-powered CO2 lasers that they can melt through metal, the blue-green argon-ion, the UV lasers that use nitrogen, and the metallic-gas combination such as He-Ag lasers (helium and silver) and Ne-Cu (neon and copper) which emit a deep violet beam.
But what about lasers used everyday? The lasers we’re going to be using are semiconductor lasers that use a small laser diode to emit a beam. They are the same lasers that are in the grocery store scanners, pen laser pointers and key chain lasers. Usually a class I or II laser, these pose minimal safety risk and are safe to use in our experiments. Here’s what you need to know:
Materials:
- laser (A key-chain laser works great. Do NOT use green lasers, which can only be used outdoors.)
- dark room
- old CD
- cut-crystal (wine glasses, fancy vases, etc) with adult help
- microscope slide or window
- cellophane and nail polish (red, green, and blue are optimal and used again in the Light Wave experiments)
- feather
- two pairs of polarized sunglasses
- frosted incandescent light bulb
Before we start building our laser projects, just play with it first. Turn off the lights at night and take your laser on a hunt around the house to see what happens when you shine it on or through different things. Here are some ideas to try:
1. Shatter the Beam: Shine your beam over the surface of an old CD. Does it work better with a scratched or smoother surface? You should see between 5-13 reflections off the surface of the CD, depending on where you shine it and how well the “seeing” conditions are.
2. Beam Scatter: Pass the laser beam through several cut-crystal objects such as wine glasses or clear glass vases. Is there a difference between clear plastic or glass, smooth or multi-faceted? Try an ice cube, both frosted and wet (clear).
3. Split the Beam: Shine the laser beam through a flat piece of glass, such as a window. Can you find the pass-through beam as well as a reflected beam? Windows and clear plastic containers will split your beam in two.
What’s going on? When you shine your laser beam through glass (like a window) or plastic (like a soda bottle filled with water and a tiny bit of cornstarch), it splits into two beams – one that passes through, and the other that internally reflects back. You can see these reflections in a darkened fog-filled room.
4. Colored Filters: Paint a piece of cellophane or stiff clear plastic with nail polish (or use colored filters) to put in the laser beam.
5. Diffraction Grating: You can make a quick diffraction grating by using a feather in the beam.
6. Polarization: If you have polarizer filters, use two. You can substitute two pairs of sunglasses. Just make sure they are polarized lenses (most UV sunglasses are). Place both lenses in the beam and rotate one 90 degrees. The lenses should block the light completely in one configuration and allow it to pass-through the other way.
Why does this happen? Polarization is a way of filtering light. Try this: in a shallow pan filled with water, make a few waves and notice how they travel from one side of the pan to the other. Now add a plastic comb, and notice how the waves stop when they hit the comb – not many pass through to the other side (watch out for the waves that creep around the edges – we’re focusing on the pass-through waves only). The comb are the sunglasses, and the water waves are the light waves.
Add a second comb at 90 degrees from the first (as you did with the sunglasses) so it resembles a mesh screen, and notice now how NONE of the waves make it through the comb array. Polarization can filter out various amounts of light, depending on the angle the combs make with each other (90 degrees apart equals total block-out).
7. Light Bulbs: In the dark, aim your laser at a frosted incandescent light bulb. The bulb will glow and have several internal reflections! What other types of light bulbs work well?
Learn more! Read up about lasers here.
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By using lenses and mirrors, you can bounce, shift, reflect, shatter, and split a laser beam. Since the laser beam is so narrow and focused, you’ll be able to see several reflections before it fades away from scatter. Make sure you complete the Laser Basics experiment first before working with this experiment.
You’ll need to make your beam visible for this experiment to really work. There are several different ways you can do this:
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1. Take your laser with you into a steamy bathroom (which has mirrors!) after a hot shower. The tiny droplets of water in the steam will illuminate your beam. (Psst! Don’t get the laser wet!)
2. If you have carpet, shine your laser under the bed while stomping the floor with your hand. The small particles (dust bunnies?) float up so you can see the beam. Some parents aren’t going to like this idea, sooo….
3. Drop a chunk of dry ice (use gloves!) into a bowl of water and use the fog to illuminate the beam. The drawback to this is that you need to keep adding more dry ice as it sublimates (goes from solid to gas) and replacing the water (when it gets too cold to produce fog).
Materials:
- large paper clips
- brass fastener
- index card
- small mirrors (mosaic-type work well)
Download Student Worksheet & Exercises
Here’s what you do: Open up each paper clip into the “L” shape. Insert a brass fastener into one U-shape leg and punch it through the card. Hot glue (or tape) one square mirror to the other end of the L-bracket. Your mirror should be upright and able to rotate. Do this with each mirror. (You can alternatively mount each mirror to a one-inch wooden cube as shown in the video.)
Turn on the laser adjust the mirrors to aim the beam onto the next mirror, and the next! Turn down the lights first and use any one of the methods mentioned above to make your laser beam visible.
What’s happening? The mirrors are bouncing the laser beam to each other, and the effect shows up when you dim the lights and add fog or dust particles to help illuminate the beam. A laser beam is a highly focused beam of light, and you can direct that light and bounce it off mirrors!
Why can’t I see the beam normally? The reason you can’t see the laser beam without the help of a steamy room, dirty carpet, or fog machine is that your eyes are tuned for green light, not red (which is why you can see the beam from a green laser at night).
Exercises
- The word LASER is actually an acronym. What does it stand for?
- What type of laser did we use in our experiment?
- Why can’t we see the laser beams without the help of steam, dirty carpet, etc.?
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Lasers are cool, but what can you do with one? This is a great introductory activity into what lasers are, how they work, and how different mediums (like glass, feathers, mirrors, etc.) can change the direction of the beam.
Lasers are a monochromatic (one color) concentrated beam of light. This means that when compared with a flashlight, the laser delivers more punch on a light detector. The alignment is more critical (as you’ll find out when you zig-zag a laser through several mirrors), so take your time and do these experiments in a steamy, dark bathroom after a hot shower. That way, you’ll be able to see the beam and align your optics easily.
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Are you ready to build your own laser theater? Here’s what you need:
- Red laser pointer (NOT GREEN!)
- 2-3 small mirrors (like mosaic mirrors)
- Feather
- 3 large paper clips
- 10 brass fasteners
- Index card
- Cardboard
- Rubber band or zip tie
- Steamy dark bathroom room (like after a hot shower with the windows covered)
- Two 3V DC motors
- Two AA battery packs
- Four AA batteries
- Three alligator wires
- Optional: plastic gem pieces
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This is a super-cool and ultra-simple circuit experiment that shows you how a CdS (cadmium sulfide cell) works. A CdS cell is a special kind of resistor called a photoresistor, which is sensitive to light.
A resistor limits the amount of current (electricity) that flows through it, and since this one is light-sensitive, it will allow different amounts of current through depends on how much light it "sees".
Photoresistors are very inexpensive light detectors, and you'll find them in cameras, street lights, clock radios, robotics, and more. We're going to play with one and find out how to detect light using a simple series circuit.
Materials:
- AA battery case with batteries
- one CdS cell
- three alligator wires
- LED (any color and type)
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Download Student Worksheet & Exercises
Turn this into a super-cool burglar alarm!
Exercises
- How is a CdS cell like a switch? How is it not like a switch?
- When is the LED the brightest?
- How could you use this as a burglar alarm?
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This is a super-cool and ultra-simple circuit experiment that shows you how a CdS (cadmium sulfide cell) works. A CdS cell is a special kind of resistor called a photoresistor, which is sensitive to light.
A resistor limits the amount of current (electricity) that flows through it, and since this one is light-sensitive, it will allow different amounts of current through depends on how much light it "sees".
Photoresistors are very inexpensive light detectors, and you'll find them in cameras, street lights, clock radios, robotics, and more. We're going to play with one and find out how to detect light using a simple series circuit.
Materials:
- AA battery case with batteries
- one CdS cell
- three alligator wires
- LED (any color and type)
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Download Student Worksheet & Exercises
Turn this into a super-cool burglar alarm!
Exercises
- How is a CdS cell like a switch? How is it not like a switch?
- When is the LED the brightest?
- How could you use this as a burglar alarm?
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This is a beefier-version of the Electric Eye that will be able to turn on a buzzer instead of a LED by increasing the voltage in the circuit. This type of circuit is a light-actuated circuit. When a beam of light hits the sensor (the "eye"), a buzzer sounds. Use this to indicate when a door closes or drawer closes... your suspect will never know what got triggered.
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Materials:
- Red laser (cheap dollar store kind works well)
- 9V Battery
- Three alligator clip leads
- Buzzer (3-6V)
- CdS Cell
Download Student Worksheet & Exercises
Exercises
- How is this circuit different from the Electric Eye experiment we did previously?
- Name three other light sources that work to activate your circuit.
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If you've already made the Laser Burglar Alarm (which is highly recommend doing FIRST), then you're probably wondering how to make the circuit act in the opposite way... meaning how do you make it so that the buzzer sounds when the light is turned off?
This circuit requires more patience and parts, but it's totally worth it. It uses the same parts as the previous experiment (plus a few more) with a couple of extra twists and turns in the circuit to let the buzzer know when it's time to turn off. Use this in doorways or as an invisible trip wire trigger across hallways.
Materials:
- Red laser pointer
- 9V battery or two AA's in a AA battery pack
- 7 alligator clip leads
- CdS Cell
- 9V Battery OR 2 AA's in a battery holder
- NPN Transistor 2N3904 or 2N222A
- 4.7k-ohm resistor
- Buzzer (3-6V)
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Why bother with the transistor? The Electric Eye & the Burglar Alarm didn't have one! The reason you can't simply substitute a buzzer for the LED in the electric eye is that the buzzer draws much more current than the CdS cell supplies. We overcame this issue in the Burglar Alarm by increasing the voltage from 3V to 9V. But how do you make the circuit detect darkness instead of light?
By using a transistor as a switch, we can make two circuits: one that triggers the transistor to turn on and off when we want it (when it sees dark, for example), and the other circuit to make the buzzer sound. We connect the two circuits by joining them together in such a way that the transistor switches the buzzer on when the CdS cell sees darkness. The transistor is our switch for the buzzer!
For younger kids, you might want to try making the trip wire alarm or the pressure sensor burglar alarm.
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What happens when you shine a laser beam onto a spinning mirror? In the Laser Maze experiment, the mirrors stayed put. What happens if you took one of those mirrors and moved it really fast?
It turns out that a slightly off-set spinning mirror will make the laser dot on the wall spin in a circle. Or ellipse. Or oval. And the more mirrors you add, the more spiro-graph-looking your projected laser dot gets.
Why does it work? This experiment works because of imperfections: the mirrors are mounted off-center, the motors wobble, the shafts do not spin true, and a hundred other reasons why our mechanics and optics are not dead-on straight. And that’s exactly what we want – the wobbling mirrors and shaky motors make the pretty pictures on the wall! If everything were absolutely perfectly aligned, all you would see is a dot.
Here’s how to do this experiment:
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Materials:
- AA battery pack with AA batteries
- two 1.5-3V DC motors OR rip them off old toys or personal fans sold in the summertime
- keychain laser pointer
- clothespin
- two round mirrors (mosaic mirrors from the craft store work great)
- two alligator clip leads
- gear that fits onto the motor and has a flat side to attach to the mirror
- 5-minute epoxy (don’t use hot glue – it’s not strong enough to hold the mirrors on at high motor speeds)
**Note – if this is your very first time wiring up an electrical circuit, I highly recommend doing this Easy Laser Light Show first. It uses a lot of the same parts, but it’s easier to build.**
Here’s what you do:
1. Insert the batteries into their case.
2. Use 5-minute epoxy to secure the gear onto the round mirror.
3. Press-fit the gear-mirror onto the shaft when the epoxy is dry.
4. Make the motor spin using the alligator clips and the battery case.
5. Turn down the lights and fire up the laser, aiming the beam onto the motor.
6. Shine the reflection somewhere easy to see, like the ceiling.
7. Once you’ve got this working, add a second mirror like you did in the laser maze.
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Advanced Two-Axis Laser Light Show
The second part of this experiment is for advanced students. What shapes can you make? Is it tough to hold it all in place? Then here’s how to create a portable laser light show:
Materials:
- Red laser pointer
- 3VDC motors
- 2 gears or corks (you’ll need a solid way to attach the mirror to the motor shaft tip)
- two 1” round mirrors (use mosaic mirrors)
- 2 DPDT switches with center off
- 20 alligator clip leads OR insulated wire if you already know how to solder
- 2 AA battery packs with 4 AA’s
- Two 1K potentiometers
- Zip-tie (from the hardware store)
- ½ ” or ¾ ” metal conduit hangers (size to fit your motors from the hardware store)
- 3 sets of ¼ ” x 2″ bolts, nuts, and washers
- 1 project container (at least 7” x 5”) with lid
- Basic tools (scissors, hot glue gun, drill, wire strippers, pliers, screwdriver)
Click here to download the Schematic Wiring Diagram for the Advanced Laser Light Show.
Download Student Worksheet & Exercises
Exercises
- How does the mirror turn a laser dot into an image?
- What happens when you add a second motor? Third?
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This super-cool project lets kids have the fun of playing tag in the dark on a warm summer evening, without the "gun" aspect traditionally found in laser tag. Kids not only get to enjoy the sport but also have the pride that they build the tag system themselves - something you simply can't get from opening up a laser tag game box.
While real laser tag games actually never use lasers, but rather infrared beams, this laser tag uses real lasers, so you'll want to arm the kids with the "no-lasers-on-the-face" with a 10-minute time-out penalty to ensure everyone has a good time. You can alternatively use flashlights instead of lasers, which makes the game a lot easier to tag someone out.
This game uses a simple two-transistor latching circuit design, so there's no programming or overly complicated circuitry to worry about. If you've never built this kind of circuit before, it's a perfect first step into the world of electronics.
I've provided you with three videos below. This first video is an introduction to what we are going to make and how it works. Here's what you need:
NOTE: We updated this circuit in 2023 to reflect "best practices" when using transistors.
Be sure to build this project as shown in the schematic and breadboard diagrams, and not as shown in the video.
The material list below is based on the new design as shown in the schematic and breadboard diagrams on this page.
The videos show how to build the old circuit, but are still very useful.
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Materials (the list below builds one complete set per kid):
Materials (the list below builds one complete set per kid):
- Two AA battery packs with batteries
- LED (any color)
- 51Ω resistor
- 10KΩ resistor
- 1KΩ resistor
- 470Ω resistor
- NPN transistor (2N3904 or 2N2222)
- PNP transistor (2N3906 or 2N4403)
- CdS Cell
- Optional: N/O pushbutton switch
- Breadboard OR soldering equipment (including wire strippers, diagonal cutters, solder...)
- Flashlight or red (NOT green!!) laser
Flashlight Laser Tag Schematic:
Flashlight laser tag breadboard diagram:
Introduction to the Circuit
The next two videos below show you how to build the circuit, first on a breadboard, and then how to solder the circuit together, so you can opt to watch either one. If you have someone who's handy with tools and soldering irons, invite them to build this with you.
Building the Circuit on a Breadboard
Soldering the Circuit Together
You'll need one of these circuits for every player, although you can get by with one kid having a flashlight (this is the "it" person) and the other running around wearing the circuit trying not to get "tagged". You can mount these circuits inside a soapbox or cardboard box with the sensor and light peeking out. Add a belt or wrist strap and you're ready for action!
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Wouldn't it be nice to wake up your brother or sister using an alarm you build yourself, triggered by natural sunlight? The happy news is now you can, using your Flashlight Laser Tag circuit you already built!
Since your circuit is already sensitive to light, you can transform it easily into an alarm clock that will buzz or light up when hit by the sun's rays.
Note - you can also use your Laser Door Alarm for this as well, since it's also triggered by light. However, the Burglar Alarm will not work, because it gets triggered by darkness, so unless you want your alarm to sound just as your drifting off to sleep, you'll want to use the Laser Door Alarm or the Flashlight Laser Tag circuit. Here's what you need to know (it's really simple...):
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Materials:
- Sunlight
- Window
- Laser Door Alarm or Flashlight Laser Tag Circuit
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In addition to laser experiments, I thought you’d like to learn how to pick up sound that’s traveling on a light wave. A crystal radio is among the simplest of radio receivers – there’s no battery or power source, and nearly no moving parts. The source of power comes directly from the radio waves (which is a low-power, low frequency light wave) themselves.
The crystal radio turns the radio signal directly into a signal that the human ear can detect. Your crystal radio detects in the AM band that have been traveling from stations (transmitters) thousands of miles away. You’ve got all the basics for picking up AM radio stations using simple equipment from an electronics store. I’ll show you how…
The radio is made up of a tuning coil (magnet wire wrapped around a toilet paper tube), a detector (germanium diode) and crystal earphones, and an antenna wire.
One of the biggest challenges with detecting low-power radio waves is that there is no amplifier on the radio to boost the signal strength. You’ll soon figure out that you need to find the quietest spot in your house away from any transmitters (and loud noises) that might interfere with the reception when you build one of these.
One of things you’ll have is to figure out the best antenna length to produce the clearest, strongest radio signal in your crystal radio. I’m going to walk you through making three different crystal radio designs.
You’ll need to find these items below.
- Toilet paper tube
- Magnet wire
- Germanium diode: 1N34A
- 4.7k-ohm resistor
- Alligator clip test leads
- 100’ stranded insulated wire (for the antenna: option 1 or option 2)
- Scrap of cardboard
- Brass fasteners (3-4)
- Telephone handset or get a crystal earphone
Here’s what you do:
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These are a set of videos made using planetarium software to help you see how the stars and planets move over the course of months and years. See what you think and tell us what you learned by writing your comments in the box below.
What’s odd about these star trails?
You can really feel the Earth rolling around under you as you watch these crazy star trails.
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Download Student Worksheet & Exercises
Do the planets follow the same arc across the night sky? You bet! All eight planets follow along the same arc that the sun follows, called the ecliptic. Here’s how the planets move across the sky:
Exercises:
- If you have constellations on your class ceiling, chart them on a separate page marking the positions of the rocks with X’s.
- Tonight, find two constellations that you will chart. Bring them with you tomorrow using the technique outlined above in Experiment.
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Ever wonder exactly how far away the planets really are? Here’s the reason they usually don’t how the planets and their orbits to scale – they would need a sheet of paper nearly a mile long!
To really get the hang of how big and far away celestial objects really are, find a long stretch of road that you can mark off with chalk. We’ve provided approximate (average) orbital distances and sizes for building your own scale model of the solar system.
When building this model, start by marking off the location of the sun (you can use chalk or place the objects we have suggested below as placeholders for the locations). Are you ready to find out what’s out there? Then let’s get started.
Materials:
- measuring tape (the biggest one you have)
- tape or chalk to mark off the locations
- 2 grains of sand or white sugar
- 12″ beach ball
- 3 peppercorns
- golf or ping pong ball
- shooter-size marble
- 2 regular-size marbles
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Download Student Worksheet & Exercises
All distances are measured from the center of the sun. (In some cases, you might just want to use the odometer in your car to help you measure the distance!
Sun (12″ beach ball) at the starting point.
Mercury (grain of sand) is 41 feet from the sun.
Venus (single peppercorn) is 77 feet from the sun.
Earth (single peppercorn) is 107 feet from the sun.
Mars (half a peppercorn) is 163 feet from the sun.
Jupiter (golf or ping pong ball) is 559 feet from the sun.
Saturn (shooter-size marble) is 1,025 feet from the sun.
Uranus (regular-size marble) is 2,062 feet from the sun.
Neptune (regular marble) is 3,232 feet from the sun.
Pluto (grain of sand) is 4,248 feet from the sun.
Nearest Star (Alpha Centauri) is 5500 miles from the sun.
Is Your Solar System Too Big?
If these distances are too large for you, simply shrink all objects to the size of the period at the end of this sentence and you’ll get your solar system to fit inside your house using these measurements below.
First, draw a tiny dot for the Sun. The diameter of the sun for this scale model is 0.1″, but we’re going to ignore this and all other planet diameters so we can fit this model within a 35′ scale.
We’re going to ignore the sizes of the planets and just focus on how far apart everything is. All distances listed below are measured from the sun. Start by marking off the position of the sun with the tip of a sharp pencil.
Here are the rest of the distances you need to mark off:
Mercury is 4 inches from the sun.
Venus is 7.75 inches from the sun.
Earth is 10 inches from the sun.
Mars is 1′ 4″ from the sun.
Jupiter is 4′ 8″ from the sun.
Saturn is 8′ 6.5″ from the sun.
Uranus is 17′ 2″ from the sun.
Neptune is 26′ 11″ from the sun.
Pluto is 35′ 5″ from the sun.
Our nearest star, Alpha Centauri, is approximately 46 miles from the sun.
Did You Notice…?
Are you mind-boggled yet? Did you notice how the solar system is really just ’empty space’? Our models shown here are too small to start bringing in the moons, but you can see why posters showing the planets are not drawn to scale. What are your thoughts on this experiment? Tell us in the comment area below!
For Advanced Students:
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If you really want to play with the different distances on your own, use this orbital calculator online to help convert the distances for you.
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After you've participated in the Planetarium Star Show (either live or by listening to the MP3 download), treat your kids to a Solar System Treasure Hunt! You'll need some sort of treasure (I recommend astronomy books or a pair of my favorite binoculars, but you can also use 'Mars' candy bars or home made chocolate chip cookies (call them Galaxy Clusters) instead.
You can print out the clues and hide these around your house on a rainy day. Did you know that I made these clues up myself as a refresher course after the astronomy presentation? Enjoy!
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Astronomy Clues
Click here to download the PDF version or the Word DOC version.
Download Student Worksheet & Exercises
You can print out images of each planet and match them up with the clues indicated below. Post images of each of the planets along with the clue for the next one to really make this an out-of-this-world experience!
The Sun (CLUE #1): Hand this one to the kids to get started.
This object is hot, but not on fire.
Explore the dryer but don’t perspire!
Mercury (CLUE #2): Hide this clue below in the dryer.
This planet is closest, but not the hottest.
Check the sock drawer, and don’t be modest!
Venus (CLUE #3): Hide this clue below in the sock drawer.
This planet is so hot it can melt a cannonball,
Crush spaceships, rain acid, and is in tree tall.
Earth (CLUE #4): Hide this clue below in a tree (or plant).
Most of this planet is covered with water.
Visit the bathtub without making it hotter.
Mars (CLUE #5): Hide this clue below in the bathtub.
This planet is basically a rusty burp.
Discover the refrigerator and take a slurp.
Jupiter (CLUE #6): Hide this clue below next to the milk.
A planet so large it can hold the rest,
Explore our library with infinite zest!
Saturn (CLUE #7): Hide this clue below with a stack of books.
This planet had rings, but not made of gold.
Explore near the front door like an astronaut bold!
Uranus (CLUE #8): Hide this clue below on the front door.
Smacked so hard it now rolls on its side,
Find the window that is ever so wide.
Neptune (CLUE #9): Hide this clue below by sticking it on a window.
Check the sink for hurricane,
gigantic blue farts, and diamond rain.
Pluto (CLUE #10): Hide this clue below near the sink with the TREASURE!
Instead of one there were two, then four…
Visit the mailbox for the one that is no more.
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You know you're not supposed to look at the sun, so how can you study it safely? I'm going to show you how to observe the sun safely using a very inexpensive filter. I actually keep one of these in the glove box of my car so I can keep track of certain interesting sunspots during the week!
The visible surface of the sun is called the photosphere, and is made mostly of plasma (remember the grape experiment?) that bubbles up hot and cold regions of gas. When an area cools down, it becomes darker (called sunspots). Solar flares (massive explosions on the surface), sunspots, and loops are all related the sun’s magnetic field. While scientists are still trying to figure this stuff out, here’s the latest of what they do know...
The sun is a large ball of really hot gas - which means there are lots of naked charged particles zipping around. And the sun also rotates, but the poles and the equator move and different speeds (don’t forget – it’s not a solid ball but more like a cloud of gas). When charged particles move, they make magnetic fields (that’s one of the basic laws of physics). And the different rotation rates allow the magnetic fields to ‘wind up’ and cause massive magnetic loops to eject from the surface, growing stronger and stronger until they wind up flipping the north and south poles of the sun (called ‘solar maximum’). The poles flip every eleven years.
There have been several satellites specially created to observe the sun, including Ulysses (launched 1990, studied solar wind and magnetic fields at the poles), Yohkoh (1991-2001, studied x-rays and gamma radiation from solar flares), SOHO (launched 1995, studies interior and surface), and TRACE (launched 1998, studies the corona and magnetic field).
Ok - so back to observing the sun form your own house. Here's what you need to do:
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Materials:
- Baader filter film
- set of eyeballs
Click here for an inexpensive Baader filter film. You can use these with your naked eye or over the OPEN END (not the eyepeice) of a telescope. See image below:
Want to see a BIG solar flare?
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Sound can change according to the speed at which it travels. Another word for sound speed is pitch. When the sound speed slows, the pitch lowers. With clarinet reeds, it’s high. Guitar strings can do both, as they are adjustable. If you look carefully, you can actually see the low pitch strings vibrate back and forth, but the high pitch strings move so quickly it’s hard to see. But you can detect the effects of both with your ears.
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The range of your ears is about 20 – 20,000 Hz (cycles per second). Bats and dogs can hear a lot higher than we can. The image (right) is a real picture of an aircraft as it breaks the sound barrier – meaning that the aircraft is passing the speed that sounds travels at (about 700 mph). The white cloud you see in the photo is related to the shock waves that are forming around the craft as it moves into supersonic speeds. You can think of a shock wave as big pressure front, which creates clouds. In this photo, the pressure from the shock waves is condensing the water vapor in the air.
There are lots of things on earth that break the sound barrier – bullets and bullwhips, for example. The loud crack from a whip is the tip zipping faster than the speed of sound.
So why do we hear a boom at all? Sonic booms are created by air pressure (think of how the water collects at the bow of a boat as it travels through the water). The vehicle pushes air molecules aside in such a way they are compressed to the point where shock waves are formed. These shock waves form two cones, at the nose and tail of the plane. The shock waves move outward and rearward in all directions and usually extend to the ground.
As the shock cones spread across the landscape along the flightpath, they create a continuous sonic boom. The sharp release of pressure, after the buildup by the shock wave, is heard as the sonic boom.
How to Make an Air Horn
Let’s learn how to make loud sonic waves… by making an air horn. Your air horn is a loud example of how sound waves travel through the air. To make an air horn, poke a hole large enough to insert a straw into the bottom end of a black Kodak film canister. (We used the pointy tip of a wooden skewer, but a drill can work also.) Before you insert the straw, poke a second hole in the side of the canister, about halfway up the side.
Here’s what you need:
- 7-9″ balloon
- straw
- film canister
- drill and drill bits
Grab an un-inflated balloon and place it on your table. See how there are two layers of rubber (the top surface and the bottom surface)? Cut the neck off a balloon and slice it along one of the folded edges (still un-inflated!) so that it now lays in a flat, rubber sheet on your table.
Drape the balloon sheet over the open end of the film canister and snap the lid on top, making sure there’s a good seal (meaning that the balloon is stretched over the entire opening – no gaps). Insert the straw through the bottom end, and blow through the middle hole (in the side of the canister).
You’ll need to play with this a bit to get it right, but it’s worth it! The straw needs to *just* touch the balloon surface inside the canister and at the right angle, so take a deep breath and gently wiggle the straw around until you get a BIG sound. If you’re good enough, you should be able to get two or three harmonics!
Download Student Worksheet & Exercises
Troubleshooting: Instead of a rubber band vibrating to make sound, a rubber sheet (in the form of a cut-up balloon) vibrates, and the vibration (sound) shoots out the straw. This is one of the pickiest experiments – meaning that it will take practice for your child to make a sound using this device. The straw needs to barely touch the inside surface of the balloon at just the right angle in order for the balloon to vibrate. Make sure you’re blowing through the hole in the side, not through the straw (although you will be able to make sounds out of both attempts).
Here’s a quick video where you can hear the small sonic boom from a bull whip:
Since most of us don’t have bull whips, might I recommend a twisted wet towel? Just be sure to practice on a fence post, NOT a person!
Exercises
- Why do we use a straw with this experiment?
- Does the length of the straw matter? What will affect the pitch of this instrument?
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This is one of my absolute favorites, because it’s so unexpected and unusual… the setup looks quite harmless, but it makes a sound worse than scratching your nails on a chalkboard. If you can’t find the weird ingredient, just use water and you’ll get nearly the same result (it just takes more practice to get it right). Ready?
NOTE: DO NOT place these anywhere near your ear… keep them straight out in front of you.
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Here’s what you need:
- water or violin rosin
- string
- disposable plastic cup
- pokey-thing to make a hole in the cup
Download Student Worksheet & Exercises
Exercises
- What does the rosin (or water) do in this experiment?
- What is vibrating in this experiment?
- What is the cup for?
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You can easily make a humming (or screaming!) balloon by inserting a small hexnut into a balloon and inflating. You can also try pennies, washers, and anything else you have that is small and semi-round. We have scads of these things at birthday time, hiding small change in some and nuts in the others so the kids pop them to get their treasures. Some kids will figure out a way to test which balloons are which without popping… which is what we’re going to do right now.
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Here’s what you need:
- hexnut
- balloon
- your lungs
Download Student Worksheet & Exercises
What to do: Place a hexnut OR a small coin in a large balloon. Inflate the balloon and tie it. Swirl the balloon rapidly to cause the hexnut or coin to roll inside the balloon. The coin will roll for a very long time on the smooth balloon surface. At high coin speeds, the frequency with which the coin circles the balloon may resonate with one of the balloon’s “natural frequencies,” and the balloon may hum loudly.
Exercises
- How does sound travel?
- What is pitch?
- How is frequency related to pitch?
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Before CDs, there were these big black discs called records. Spinning between 33 and 45 times per minute on a turntable, people used to listened to music just like this for nearly a century. Edison, who had trouble hearing, used to bite down hard on the side of his wooden record player (called a phonograph) and “hear” the music as it vibrated his jaw.
Many people today still think that records still sound better than CDs (I think they do), especially if the record is well cared for and their players are tuned just right. Here’s a video on how a record works:
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Here’s what you need:
- an old turntable (do you have one in your garage?)
- old record that can be scratched
- tack
- plastic container, like a clean yogurt or butter tub
If you have an old turntable and OLD record that can be scratched, here’s how to listen to the music without using regular speakers!
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Bobsleds use the low-friction surface of ice to coast downhill at ridiculous speeds. You start at the top of a high hill (with loads of potential energy) then slide down a icy hill til you transform all that potential energy into kinetic energy. It’s one of the most efficient ways of energy transformation on planet Earth. Ready to give it a try?
This is one of those quick-yet-highly-satisfying activities which utilizes ordinary materials and turns it into something highly unusual… for example, taking aluminum foil and marbles and making it into a racecar.
While you can make a tube out of gift wrap tubes, it’s much more fun to use clear plastic tubes (such as the ones that protect the long overhead fluorescent lights). Find the longest ones you can at your local hardware store. In a pinch, you can slit the gift wrap tubes in half lengthwise and tape either the lengths together for a longer run or side-by-side for multiple tracks for races. (Poke a skewer through the rolls horizontally to make a quick-release gate.)
Here’s what you need:
- aluminum foil
- marbles (at least four the same size)
- long tube (gift wrapping tube or the clear protective tube that covers fluorescent lighting is great)
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If you’re finding that the marbles fall out before the bobsled reaches the bottom of the slide, you need to either crimp the foil more closely around the marbles or decrease your hill height.
Check to be sure the marbles are free to turn in their “slots” before launching into the tube – if you’ve crimped them in too tightly, they won’t move at all. If you oil the bearings with a little olive oil or machine oil, your tube will also get covered with oil and later become sticky and grimy… but they sure go faster those first few times!
Download Student Worksheet & Exercises
Exercises Answer the questions below:
- Potential energy is energy that is related to:
- Equilibrium
- Kinetic energy
- Its system
- Its elevation
- If an object’s energy is mostly being used to keep that object in motion, we can say it has what type of energy?
- Kinetic energy
- Potential energy
- Heat energy
- Radiation energy
- True or False: Energy is able to remain in one form that is usable over and over again.
- True
- False
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We're going to build monster roller coasters in your house using just a couple of simple materials. You might have heard how energy cannot be created or destroyed, but it can be transferred or transformed (if you haven't that's okay - you'll pick it up while doing this activity).
Roller coasters are a prime example of energy transfer: You start at the top of a big hill at low speeds (high gravitational potential energy), then race down a slope at break-neck speed (potential transforming into kinetic) until you bottom out and enter a loop (highest kinetic energy, lowest potential energy). At the top of the loop, your speed slows (increasing your potential energy), but then you speed up again and you zoom near the bottom exit of the loop (increasing your kinetic energy), and you're off again!
Here's what you need:
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- marbles
- masking tape
- 3/4" pipe foam insulation (NOT neoprene and NOT the kind with built-in adhesive tape)
To make the roller coasters, you'll need foam pipe insulation, which is sold by the six-foot increments at the hardware store. You'll be slicing them in half lengthwise, so each piece makes twelve feet of track. It comes in all sizes, so bring your marbles when you select the size. The ¾” size fits most marbles, but if you’re using ball bearings or shooter marbles, try those out at the store. (At the very least you’ll get smiles and interest from the hardware store sales people.) Cut most of the track lengthwise (the hard way) with scissors. You’ll find it is already sliced on one side, so this makes your task easier. Leave a few pieces uncut to become “tunnels” for later roller coasters.
Read for some 'vintage Aurora' video? This is one of the very first videos ever made by Supercharged Science:
Download Student Worksheet & Exercises
Tips & Tricks
Loops Swing the track around in a complete circle and attach the outside of the track to chairs, table legs, and hard floors with tape to secure in place. Loops take a bit of speed to make it through, so have your partner hold it while you test it out before taping. Start with smaller loops and increase in size to match your entrance velocity into the loop. Loops can be used to slow a marble down if speed is a problem.
Camel-Backs Make a hill out of track in an upside-down U-shape. Good for show, especially if you get the hill height just right so the marble comes off the track slightly, then back on without missing a beat.
Whirly-Birds Take a loop and make it horizontal. Great around poles and posts, but just keep the bank angle steep enough and the marble speed fast enough so it doesn’t fly off track.
Corkscrew Start with a basic loop, then spread apart the entrance and exit points. The further apart they get, the more fun it becomes. Corkscrews usually require more speed than loops of the same size.
Jump Track A major show-off feature that requires very rigid entrance and exit points on the track. Use a lot of tape and incline the entrance (end of the track) slightly while declining the exit (beginning of new track piece).
Pretzel The cream of the crop in maneuvers. Make a very loose knot that resembles a pretzel. Bank angles and speed are the most critical, with rigid track positioning a close second. If you’re having trouble, make the pretzel smaller and try again. You can bank the track at any angle because the foam is so soft. Use lots of tape and a firm surface (bookcases, chairs, etc).
Troubleshooting Marbles will fly everywhere, so make sure you have a lot of extras! If your marble is not following your track, look very carefully for the point of departure – where it flies off.
-Does the track change position with the weight of the marble, making it fly off course? Make the track more rigid by taping it to a surface.
-Is the marble jumping over the track wall? Increase your bank angle (the amount of twist the track makes along its length).
-Does your marble just fall out of the loop? Increase your marble speed by starting at a higher position. When all else fails and your marble still won’t stay on the track, make it a tunnel section by taping another piece on top the main track. Spiral-wrap the tape along the length of both pieces to secure them together.
HOT TIPS for ULTRA-COOL PARENTS: This lab is an excellent opportunity for kids to practice their resilience, because we guarantee this experiment will not work the first several times they try it. While you can certainly help the kids out, it’s important that you help them figure it out on their own. You can do this by asking questions instead of rushing in to solve their problems. For instance, when the marble flies off the track, you can step back and say:
“Hmmm… did the marble go to fast or too slow?”
“Where did it fly off?”
“Wow – I’ll bet you didn’t expect that to happen. Now what are you going to try?”
Become their biggest fan by cheering them on, encouraging them to make mistakes, and try something new (even if they aren’t sure if it will work out).
Check out this cool roller coaster from one of our students!
Exercises
- What type of energy does a marble have while flying down the track of a roller coaster?
- What type of energy does the marble have when you are holding it at the top of the track?
- At the top of a camel back hill, which is higher for the marble, kinetic or potential energy?
- At the top of an inverted loop, which energy is higher, kinetic or potential energy?
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A super-fast, super-cool car that uses the pent-up energy inside a mouse trap spring to propel a homemade car forward. While normally this is reserved for high school physics classes, it really is a fun and inexpensive experiment to do with kids of all ages.
This is a great demonstration of how energy changes form. At first, the energy was stored in the spring of the mousetrap as elastic potential energy, but after the trap is triggered, the energy is transformed into kinetic energy as rotation of the wheels.
Remember with the First Law of Thermodynamics: energy can’t be created or destroyed, but it CAN change forms. And in this case, it goes from elastic potential energy to kinetic energy.
There’s enough variation in design to really see the difference in the performance of your vehicle. If you change the size of the wheels for example, you’ll really see a difference in how far it travels. If you change the size of the wheel axle, your speed is going to change. If you alter the size of the lever arm, both your speed and distance will change. It's fun to play with the different variables to find the best vehicle you can build with your materials!
Here's what you need to do this project:
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Materials:
Since the directions for this project are complex, it’s really best to watch the instructions on the video. Here are the highlights:
1. Tape the dowel to the outside of the wire on the mousetrap car (see image below). When the mousetrap spans closed, the dowel whips through the air along with it in an arc.
2. Attach a length of fishing line to the other end of the dowel. Don’t cut the fishing line yet.
3. Attach one straw near each end of a block of foam using hot glue.
4. Insert a skewer into each straw. Insert a wheel onto each end of the skewer. This is your wheel-axel assembly.
5. The wheels on one side should be close to the straw, the wheels on the other end should have a 1/2” gap.
6. Thread the end of the fishing line around the wheels with the gap as shown in the video.
7. Load the mousetrap car by spinning the back wheels as you set the trap.
8. Trigger the mousetrap with a pen (never use your fingers!). The dowel pulls the fishing line, unrolling it from the axel and spinning the wheels as it opens.
Energy has a number of different forms; kinetic, potential, thermal, chemical, electrical, electrochemical, electromagnetic, sound and nuclear. All of which measure the ability of an object or system to do work on another object or system.
In the physics books, energy is the ability to do work. Work is the exertion of force over a distance. A force is a push or a pull.
So, work is when something gets pushed or pulled over a distance against a force. Mathematically:
Work = Force x Distance or W = F d
Let me give you a few examples: If I was to lift an apple up a flight of stairs, I would be doing work. I would be moving the apple against the force of gravity over a distance. However, if I were to push against a wall with all my might, and if the wall never moved, I would be doing no work because the wall never moved. (There was a force, but no distance.)
Another way to look at this, is to say that work is done if energy is changed. By pushing on the non-moving wall, no energy is changed in the wall. If I lift the apple up a flight of stairs however, the apple now has more potential energy then it had when it started. The apple’s energy has changed, so work has been done.
All the different forms of energy can be broken down into two categories: potential and kinetic energy.
My students have nicknamed potential energy the “could” energy. The battery “could” power the flashlight. The light “could” turn on. I “could” make a sound. That ball “could” fall off the wall. That candy bar “could” give me energy.
Potential energy is the energy that something has that can be released. For example, the battery has the potential energy to light the bulb of the flashlight if the flashlight is turned on and the energy is released from the battery. Your legs have the potential energy to make you hop up and down if you want to release that energy (like you do whenever it’s time to do science!). The fuel in a gas tank has the potential energy to make the car move.
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This is a great demonstration of how energy changes form. At first, the energy was stored in the spring of the mousetrap as elastic potential energy, but after the trap is triggered, the energy is transformed into kinetic energy as rotation of the wheels.
Remember with the First Law of Thermodynamics: energy can’t be created or destroyed, but it CAN change forms. And in this case, it goes from elastic potential energy to kinetic energy.
There’s enough variation in design to really see the difference in the performance of your vehicle. If you change the size of the wheels for example, you’ll really see a difference in how far it travels. If you change the size of the wheel axle, your speed is going to change. If you alter the size of the lever arm, both your speed and distance will change. It's fun to play with the different variables to find the best vehicle you can build with your materials!
Here's what you need to do this project:
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Materials:
- Mousetrap (NOT a rat trap)
- Foam block or piece of cardboard
- Four old CDs
- Thin string or fishing line
- Wood dowel or long, straight piece from a wire coat hanger (use pliers to straighten it)
- Straw
- Two wood skewers (that fit inside straw)
- Hot glue gun
- Duct tape
- Scissors
- Four caps to water bottles
- Drill
- Razor with adult help
Since the directions for this project are complex, it’s really best to watch the instructions on the video. Here are the highlights:
1. Tape the dowel to the outside of the wire on the mousetrap car (see image below). When the mousetrap spans closed, the dowel whips through the air along with it in an arc.
2. Attach a length of fishing line to the other end of the dowel. Don’t cut the fishing line yet.
3. Attach one straw near each end of a block of foam using hot glue.
4. Insert a skewer into each straw. Insert a wheel onto each end of the skewer. This is your wheel-axel assembly.
5. The wheels on one side should be close to the straw, the wheels on the other end should have a 1/2” gap.
6. Thread the end of the fishing line around the wheels with the gap as shown in the video.
7. Load the mousetrap car by spinning the back wheels as you set the trap.
8. Trigger the mousetrap with a pen (never use your fingers!). The dowel pulls the fishing line, unrolling it from the axel and spinning the wheels as it opens.
What’s Going On?
Energy has a number of different forms; kinetic, potential, thermal, chemical, electrical, electrochemical, electromagnetic, sound and nuclear. All of which measure the ability of an object or system to do work on another object or system.
In the physics books, energy is the ability to do work. Work is the exertion of force over a distance. A force is a push or a pull.
So, work is when something gets pushed or pulled over a distance against a force. Mathematically:
Work = Force x Distance or W = F d
Let me give you a few examples: If I was to lift an apple up a flight of stairs, I would be doing work. I would be moving the apple against the force of gravity over a distance. However, if I were to push against a wall with all my might, and if the wall never moved, I would be doing no work because the wall never moved. (There was a force, but no distance.)
Another way to look at this, is to say that work is done if energy is changed. By pushing on the non-moving wall, no energy is changed in the wall. If I lift the apple up a flight of stairs however, the apple now has more potential energy then it had when it started. The apple’s energy has changed, so work has been done.
All the different forms of energy can be broken down into two categories: potential and kinetic energy.
My students have nicknamed potential energy the “could” energy. The battery “could” power the flashlight. The light “could” turn on. I “could” make a sound. That ball “could” fall off the wall. That candy bar “could” give me energy.
Potential energy is the energy that something has that can be released. For example, the battery has the potential energy to light the bulb of the flashlight if the flashlight is turned on and the energy is released from the battery. Your legs have the potential energy to make you hop up and down if you want to release that energy (like you do whenever it’s time to do science!). The fuel in a gas tank has the potential energy to make the car move.
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Ever wonder how magicians work their magic? This experiment is worthy of the stage with a little bit of practice on your end.
Here’s how this activity is laid out: First, watch the video below. Next, try it on your own. Make sure to send us your photos of your inventions here!
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For this incredibly easy, super-amazing experiment, you’ll need to find:
- a plastic cup
- hard covered book
- toilet paper tube
- a ball that’s a bit smaller then the opening of the cup but larger than the opening of the toilet paper tube (you can also use an egg when you really get good at this trick!)
1. Put the cup on a table.
2. Put the book on top of the cup.
3. This is the tricky part. Put the toilet paper tube upright on the book, exactly over the cup.
4. Now put the ball on top of the toilet paper tube.
5. Check again to make sure the tube and the ball are exactly over the top of the cup.
6. Now, hit the book on the side so that it moves parallel to the table. You want the book to slide quickly between the cup and the tube.
7. If it works right, the book and the tube fly in the direction you hit the book. The ball however falls straight down and into the cup.
8. If it works say TAAA DAAA!
Download Student Worksheet & Exercises
This experiment is all about inertia. The force of your hand got the book moving. The friction between the book and the tube (since the tube is light it has little inertia and moves easily) causes the tube to move. The ball, which has a decent amount of weight, and as such a decent amount of inertia, is not effected much by the moving tube. The ball, thanks to gravity, falls straight down and, hopefully, into the cup. Remember the old magician’s trick of pulling the table cloth and leaving everything on the table? Now you know how it’s done. “Abra Inertia”!
So inertia is how hard it is to get an object to change its motion, and Newton’s First Law basically states that things don’t want to change their motion. Get the connection?
Exercises
- What are two different pairs of forces in this experiment?
- Explain where Newton’s Three Laws of motion are observed in this experiment.
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Sound is everywhere. It can travel through solids, liquids, and gases, but it does so at different speeds. It can rustle through trees at 770 MPH (miles per hour), echo through the ocean at 3,270 MPH, and resonate through solid rock at 8,600 MPH.
Sound is made by things vibrating back and forth, whether it’s a guitar string, drum head, or clarinet. The back and forth motion of an object (like the drum head) creates a sound wave in the air that looks a lot like a ripple in a pond after you throw a rock in. It radiates outward, vibrating it’s neighboring air molecules until they are moving around, too. This chain reaction keeps happening until it reaches your ears, where your “sound detectors” pick up the vibration and works with your brain to turn it into sound.
You can illustrate this principle using a guitar string – when you pluck the string, your ears pick up a sound. If you have extra rubber bands, wrap them around an open shoebox to make a shoebox guitar. You can also cut a hole in the lid (image left) and use wooden pencils to lift the rubber band off the surface of the shoebox.
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Materials:
- index card
- rubber band
- 3′ string
- small piece of craft foam sheet OR a second index card
- hot glue and glue sticks
- tape
Download Student Worksheet & Exercises
Why is this happening? When you sling the hornet around, wind zips over the rubber band and causes it to vibrate like a guitar string… and the sound is focused (slightly) by the card. The card really helps keep the contraption at the correct angle to the wind so it continues to make the sound.
Troubleshooting: Most kids forget to put on the rubber band, as they get so excited about finishing this project that they grab the string and start slinging it around… and wonder why it’s so silent! Make sure they have a fat enough rubber band (about 3.5” x ¼ “ – or larger) or they won’t get a sound.
Variations include: multiple rubber bands, different sizes of rubber bands, and trying it without the index card attached. The Buzzing Hornet works because air zips past the rubber band, making it vibrate, and the sound gets amplified just a bit by the index card.
Exercises
- What effect does changing the length of the string have on the pitch?
- What vibrates in this experiment to create sound?
- Why do we use an index card?
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Your voice is a vibration, and you can feel it when you place a hand on your throat when you speak. As long as there are molecules around, sound will be traveling though them by smacking into each other.
That’s why if you put an alarm clock inside a glass jar and remove the air, there’s no sound from the clock. There’s nothing to transfer the vibrational energy to – nothing to smack into to transfer the sound. It’s like trying to grab hold of fog – there’s nothing to hold on to.
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Here’s what you need:
- two tongue depressors
- three rubber bands, one at least 1/4″ wide
- paper
- tape
Download Student Worksheet & Exercises
What’s going on? The rubber band vibrates as you blow across the rubber band and you get a great sound. You can change the pitch by sliding the cuffs (this does take practice).
Troubleshooting: This project is really a variation on the Buzzing Hornets, but instead of using wind to vibrate the string, you use your breath. The rubber band still vibrates, and you can change the vibration (pitch) by moving the cuffs closer together or further apart. If the cuffs don’t slide easily, just loosen the rubber bands on the ends. You can also make additional harmonicas with different sizes of rubber bands, or even stack three harmonicas on top of each other to get unusual sounds.
If you can’t get a sound, you may have clamped down too hard on the ends. Release some of the pressure by untwisting the rubber bands on the ends and try again. Also – this one doesn’t work well if you spit too much – wet surfaces keep the rubber band from vibrating.
Exercises
- What is sound?
- What is energy?
- What is moving to make sound energy?
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You probably already know how to tie your shoes, I know. But what you may not know is how to tie them so they don't become loose easily and are fast to untie... faster than a regular double-knot. Here's how:
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