eCamp

Homemade Natural History Museum

Thursday May 16, 2024

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Summer is a great time to be outdoors and explore the world around you! The days are filled with taking nature walks, discovering hiking trails, spending the afternoon exploring the sea shore… it’s limitless!

Even though it doesn’t look like “learning” (no textbook, no desk…), kids will learn much more by being in nature than they ever will reading about it. It’s a fantastic opportunity for kids to learn how to observe animal behavior, discover how to use their field instruments like microscopes and telescopes, and really be amazed at the diversity in their local ecosystem.

This summer, discover what nature has to offer by building a homemade natural history museum! Kids will collect, explore and curate things from nature and then study selected pieces and put them on display with their own identification cards. Kids will also be the ones to lead guests through their collections and answer questions about the treasures they have gathered.

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Download the Natural History Museum Packet

Once your natural history museum is open, take a guided video tour and send it to me so I can see what you’ve created! Here’s my email: [email protected]

Paper Enigma Machine

Wednesday August 5, 2020

Secret codes and ciphers are so much fun to learn about and create! This particular secret code machine is a simpler model of the original that was so complex, it took a brilliant mathematician, Alan Turing, to devise the techniques which cracked the code.

In order to create this paper machine, you’ll need the templates which you can find here. Before you print and cut them out, watch the first part of the video, because chances are, you’re going to have to re-size it so it will fit your container.

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Materials:

Pringles Chip can (empty)
Tape
Scissors
Color printout of the templates

Here’s what you do to use this machine:

Line up the fray bars on the reflector and input/output (this is your start position)
Decide on a 3-letter key. You can use ABC, CAT, DOG… any three you want. Write these down now.
Turn the rotors so that the three letters of your KEY are lined up.
What is the message you want to encode? Choose a short message to start with.
For each letter of your message, turn JUST THE RIGHT ROTOR one step towards you (to the letter in line with the gray alignment bar goes to the next one in the alphabet).
Do NOT turn the reflector or the input/output cylinders!
You need to turn it ONCE BEFORE you start encoding.
Now find the letter from your message on the input/output cylinder and trace it through all three rotors, reflector, and back through all three rotors and back to the input/output cylinder. Write down your encoded first letter!
Continue to work your way through your message… read the next couple of points before finishing…

Rotor Turnover

You’ll notice that all three rotors have a shaded gray letter. This will help scramble up your message even more. Here’s how to handle it:

If the middle rotor is gray, TURN ALL THREE rotors one step toward you (this may be easier to do one at a time).
If the letter on just the right rotor is gray, turn the MIDDLE AND RIGHT rotors one step toward you.
If none are gray, just turn the right rotor one step toward you.
The gray on the LEFT rotor is not used. It’s there in case that rotor changes position to be a middle or right rotor in the future.
If you follow all the turnover rules, you might find that you have a gray shaded letter on the middle rotor that steps into position when turning over. If that happens, you need to DOUBLE STEP, meaning that ALL THREE ROTORS (not just the middle rotor) must step again when the next letter is processed. Try this out to make sure you understand how to do it:

Use rotors I, II, & III and key A D S to decipher this message:

R Z F O G F Y H P L

You should end up with two words you recognize and the rotors at positions B F C.

Enjoy your enigma machine!

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Introduction to Flying Machines

Saturday May 16, 2020

You’re going to do several experiments that change air pressure and mystify your kids. The goal is to set them thinking about how and why things fly (you’ll do this by learning about air pressure and Bernoulli’s law).

While you are playing with the experiments in the video, see if you can notice these important ideas:

Air pressure is all around us.
Air pushes downward and creates pressure on all things.
Air pressure changes all the time.
Higher pressure always pushes.
The faster air travels over a surface, the less time it has to push down on that surface and create pressure. Fast moving air creates low pressure regions.
The four fundamental forces on an airplane are lift, weight, thrust, and drag.

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Summer Camp Main Menu

Tuesday April 21, 2020

Easy Photoelectric Effect Experiment

Saturday July 1, 2017

Photoelectric Effect Einstein received a Nobel Prize for figuring out what happens when you shine blue light on a sheet of metal. When he aimed a blue light on a metal plate, electrons shot off the surface. (Metals have electrons which are free to move around, which is why metals are electrically conductive. More on this in Unit 10).

When Einstein aimed a red light at the metal sheet, nothing happened. Even when he cranked the intensity (brightness) of the red light, still nothing happened. So it was the energy of the light (wavelength), not the number of photons (intensity) that made the electrons eject from the plate. This is called the ‘photoelectric effect’. Can you imagine what happens if we aim a UV light (which has even more energy than blue light) at the plate?

This photoelectric effect is used by all sorts of things today, including solar cells, electronic components, older types of television screens, video camera detectors, and night-vision goggles.

This photoelectric effect also causes the outer shell of orbiting spacecraft to develop an electric charge, which can wreck havoc on its internal computer systems.

A surprising find was back in the 1960s, when scientists discovered that moon dust levitated through the photoelectric effect. Sunlight hit the lunar dust, which became (slightly) electrically charged, and the dust would then lift up off the surface in thin, thread-like fountains of particles up ¾ of a mile high.

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Materials:

soda or steel can
paper clip
sand paper
tinsel (or aluminum foil and scissors)
tape
foam cup
PVC pipe (any size)
brown paper bag
UV shortwave lamp (sometimes called a “germ-free portable lamp”)

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Introduction to Flying Machines

Sunday November 20, 2016

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While you are playing with the experiments in the video, see if you can notice these important ideas:

Air pressure is all around us.
Air pushes downward and creates pressure on all things.
Air pressure changes all the time.
Higher pressure always pushes.
The faster air travels over a surface, the less time it has to push down on that surface and create pressure. Fast moving air creates low pressure regions.
The four fundamental forces on an airplane are lift, weight, thrust, and drag.

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Straw Rubber Band Rocket

Tuesday May 31, 2016

Simple rockets are not only fun to launch, but teach kids the basics of fin design (how many fins are best?), projectile motion(does launch angle matter for furthest distance), and basic construction (can you really make fins from just tape itself?). Let your kid's imagination soar with this easy and fun project. [am4show have='p8;p9;p10;p37;p95;' guest_error='Guest error message' user_error='User error message' ] Materials:

straw
rubber band
skewer
scissors
tape

What happens if you strap this to a paper airplane? [/am4show]

Spinning Ring

Tuesday May 31, 2016

Flying machines are just plain awesome, and ones that can fly without really looking like they should are even better! Throw this one like a football for longer flights!

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Airfoil

Tuesday May 31, 2016

The Ancient Chinese discovered that kites with curved surfaces flew better than kites with flat surfaces. A wing needs to have camber: the top needs to be slightly curved, like a bump, and the bottom is straight.

This is called an airfoil. Airfoils are designed to generate as much lift as possible with as little drag as possible. Here’s how you make an airfoil:

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Materials:

index card

tape

skewer or pencil

First, you set up how wide you want your wing to be. This is a chord line. One point on the chord line is the leading edge and one is the trailing edge.

Now add camber by pushing up the top surface until it curves. Now push that bump to the left so it’s more curved at the leading edge. How thick you make this will depend on how fast your wing is going to go and how much lift you need.

Now add the same thickness under the camber line to make the lower surface. Now you have an airfoil!

The airfoil uses Bernoulli’s principle. The top surface of the wing has more camber than the bottom surface, which means that air will flow faster over the top than it does underneath. This means that there’s less air pressure above the wing than under it, and this difference in air pressure makes lift.

How much lift? Well that depends on the airfoil shape, the size and shape of the wing, the angle it makes with the air, the density of the air, and how fast it’s going. Airplanes designed to fly slow have thicker airfoils than supersonic aircraft because the air flows slightly differently at fast versus slow speeds. Airplanes flying at high altitudes have less air molecules to generate lift in the same amount of air as lower flying planes.

If you’ve ever heard of “stalls”, it’s different when an airplane stalls than when a car stalls. What happens when a car stalls? The engine stops, right? If the engine stops in an airplane, it’s called an engine failure, not a stall. A stall is when the air stops flowing over the wing. The engine in an airplane can stop but air can still go over the wing, right? During an engine failure, a propeller airplane turns into a glider, which still can fly. So a stall happens when the wing tips up so high that air can’t flow over the top, so there’s no lower pressure and therefore no lift. If there’s no lift, the airplane turns basically into a rock and falls.

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MIT Leg Lab

Wednesday July 1, 2015

Back in the 1980s, MIT did some amazing work in the field of robots with legs. Here's a video compilation from the Discovery Channel and their own Leg Lab work:

To learn more, visit http://www.ai.mit.edu/projects/leglab/home.html

Drop Rocket with Launcher

Sunday May 31, 2015

You get to not only build as many rockets as you want, but also the launcher to go with it! Although the launcher takes about 20 minutes to assemble, it will serve you for thousands of rocket launches, and doesn’t require an air compressor or even a bike pump! You’re going to make your own single-piston air pump using everyday hardware store parts. You can opt to include the protractor if you want to be more precise in your measurements. You can use this experiment in more advanced projects, like science fairs. See tips below for more information. [am4show have='p8;p9;p10;p37;p95;' guest_error='Guest error message' user_error='User error message' ] Materials: Rocket

Straw
Masking tape
Small ball of clay

Launcher Note: In the video, I use 2" and 1-1/4" PVC for the inner piston. For a smaller, less expensive model, substitute 1-1/4" PVC pipe and fittings for the 2", and 1" for the 1-1/4" PVC pipe and fittings. You will not need to wrap the inner piston if you choose the smaller size.

2” PVC pipe approx. 2’ long
1 1/4” PVC pipe approx. 2’ long
1/2” PVC pipe approx. 6” long
1-1/4” PVC end cap
1/2” PVC plug
1/2” PVC elbow
2” to 1/2” PVC reducer
2” PVC elbow
3/16” brass tubing
PVC cement
Hot glue
2” pipe clamp
2 wood screws
Electrical tape
Protractor (optional)
Drill and drill bits (3/16”)
Scrap piece of wood

After the initial fun, you may start to wonder about how you can use this as a science fair project or something that really does some real science. This is a great setup for this type of experimenting, since you can do repeated launches and measure your results. The first thing you’ll need to do is figure out a way to make it so that you push down with the same amount of force each time you launch the rocket. You can attach a bungee cord to connect the cap of the 1-1/4” PVC pipe to the opening of the 2” PVC pipe, and add small increments on the 1-1/4” pipe. This experiment can show the effect of gravity of different masses of rockets, since the speed of the rocket is the same at all angles fired at (if you launch with the same force each time). You can also vary the launch angle and measure how far the rocket goes horizontally each time, or make the vertical measurement tool shown in the video as well. You can experimentally figure out the best angle to launch at, since if you launch completely vertical, all the energy goes into making the rocket move vertically and it doesn't travel any vertical distance, and lets drag stop the rocket while it’s still in the air. If you aim it near the horizontal, there’s less energy available to overcome the pull of gravity, so it doesn't fly nearly as high and it hits the ground and drags to a stop, wasting energy. There’s a “best launch angle” that balances these two effects to make a parabolic trajectory (path) that the rocket takes when launched. Other ideas including carrying the nose-weight of the rocket. You’ll need to be able to measure the clay (in grams) and see what effect this has on flight as well. Try a rocket without any clay at all and see how it flies! Use a pencil tip or an edge of a ruler to balance each rocket and find it’s center of gravity, and measure this from the nose and record this with your data in a table. What happens if you change the size, shape, and location of the fins? What if you put fins in the front, middle or back of the straw? Use big or small fins? [/am4show]

Hybrid Rockets

Monday May 25, 2015

When I was in graduate school, I studied rockets quite a bit, specifically the nozzle section. We had an experiment set up we called the “glass rocket” because the burning section was made of acrylic, and it was really only used to amaze people when they come in to tour our lab. Although that I wasn’t able to get a video made of that particular rocket, I found one even better that not only shows the same principle and experiment, but also shows you how to built one yourself… if you really know what you are doing.

I can imagine most folks not being able to build one of these themselves… it is a bit intimidating! The video below shows you how to build a much easier version using yeast, hydrogen peroxide, and pasta. The pasta contains hydrocarbons and serves the same purpose as the acrylic in the previous video (above).

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Materials:

uncooked pasta tubes with flat ends
yeast
hydrogen peroxide
clean mason jar with lid (NO ring) – cut an 1/8″ hole in the center of the lid
lighter with adult help

The oxygen flow is generated from the hydrogen peroxide. The hydrogen peroxide molecule looks a lot like the water molecule, only it has an extra oxygen atom. When you add the yeast to the peroxide, it acts as a catalyst and breaks off that extra oxygen, which bubbles up and out of the hole in the lid. It’s important that you don’t screw the lid onto the jar – just rest the lid (without the screw-on ring) on top of the jar.

Since there’s no nozzle on the end of the pasta (although I can imagine how you might wet the pasta and shape it a bit before allowing it to dry), the fluid is going to be pretty slow out the exit tube. We’re also not adjusting the flow at all – it’s flowing at the rate it’s being generated inside the jar.

This particular rocket is a hybrid rocket, which means it uses a solid fuel source (the hydrocarbons in the pasta) and a liquid or gas oxidizer (which is the oxygen from the peroxide reaction). The nice thing about this particular kind of rocket is that you can shut it off if things goes wrong (which you can’t do with solid state rockets, like Estes model rockets or most fireworks). Since the fuel is in a solid state, there’s no big explosion hazard like there is with liquid fuel rockets (imagine having a tank of liquid hydrogen… that’s a big explosion just waiting to happen).

The same type of rocket engine (hybrid) was used in Space Ship One!

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Quick ‘n Easy Slingshot Rockets

Sunday May 24, 2015

There's really nothing better than making a rocket in less than 5 minutes that can shoot clear across the room using stuff you'd find in a desk or kitchen drawer. Here's how you do it: [am4show have='p8;p9;p10;p37;p109;p95;' guest_error='Guest error message' user_error='User error message' ] Materials:

index card
paperclip
rubber band
straw
popsicle stick
tape
scissors

If you're having trouble with the rocket catching on the end of the rubber band, make the "hook" part smaller. Bend it straight again, and then re-bend it so there's not quite so much of it hanging down. You can also adjust the angle so it's more than a 90 degree bend so it will release quicker. Play with the design and see what kind of improvements you can think up! [/am4show]

Forensics Shopping List

Sunday April 19, 2015

Here’s a list of the supplies you’ll need to complete most of the basic experiments in this series:

5 Microscope slides
2 magnifying lenses (handheld type)
Sunglasses (ones that are okay to glue stuff to)
2 small mirrors (mosiac mirrors from a craft store work well)
Current denominations ($1, $5, $10 and higher if possible) bills
Hair samples
Cobalt chloride
Cotton swab
Goggles
Crayon
Test tube with stopper
Index card
Lemon juice
Distilled water
Hair dryer
Hot glue and glue sticks
Scissors
Tape
Microscope (optional)

Note that the more advanced experiments, including the laser alarms, trip wire, pressure sensors, laser maze, and laser transmitters have their own individual materials listed with each experiment. Please refer to each experiment for a full and complete itemized material list with order links.

Fingerprinting

Sunday April 19, 2015

Note: there are FOUR videos on this page, and FIVE experiments!

Every crime scene has a silent witness called physical evidence, and fingerprints are one kind of physical evidence. The patterns of ridges on both the finger and toe are unique to each person; no two are alike, which allows fingerprinting to help identify who did what, when, and where. Your fingerprint pattern will never change throughout your entire lifetime, which makes it a handy tool for identification. The main patterns are arch, loop, and whorl.

Fingerprints are friction ridges made up of a single row of pores in your skin. When your finger touches a surface, oil and sweat transfer from your finger to the surface and leave an impression of the ridge pattern from your finger.

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There are three types of fingerprints: plastic, patent, and latent. Plastic is when a fingerprint is intended and makes a three-dimensional impression, like pressing your finger onto soft wax. Patent fingerprints are visible – these are the ones your mom gets upset about when she sees your prints all over her mirror or windows. The most common type of fingerprint is the invisible mark (latent), which require either a chemical reaction to be made visible or physical treatment.

Materials:

pen
index card (or download this FBI fingerprint card)
number 2 pencil and pencil sharpener
3/4″ transparent sticky tape
magnifying glass
ink pad
photocopier
small ball of clay (golf ball size)
4 microscope slides
graphite powder with adult supervision
goggles and gloves
paint brush or old makeup brush
disposable paper cup
scissors
clear silicone (hardware store) OR gummy bear candy (see variation step #11 in Experiment Part 3)
4″ square of aluminum foil
3 feet of string
string
duct tape
empty clean glass jar with a lid (pickle, jam ,or mayo jars work great)
black sheet of paper
crazy glue or super glue
black objects (glass, metal, or plastic)
iodine crystals (adults only)

Experiment Part 1: Lifting Patent Fingerprints

Sharpen your pencil.
Lay a piece of tape down sticky-side up by touching only the edge of the tape.
Rub your pencil on your fingertip using the side of the pencil.
Touching the finger to the sticky side of the tape.
Gently pull your finger from the tape and pace it on the card. Trim off any excess tape.
Repeat for all fingers (and toes if you wish).
Carefully examine the prints under a magnifying glass. What type of fingerprint do you have? Look at the ridge pattern (loop, arch, or whorl). You can use a photocopier to enlarge the prints so they are easier to see.
Are the prints clearer and easier to read using an ink pad or a pencil?

Experiment Part 2: Lifting Latent Fingerprints

(This next part works well if you have two friends to help you out.)

Clean all microscope slides using a soft cloth.
Close your eyes and ask one of your friends to secretly (without telling you which friend) rub their finger against the side of the nose or across the forehead (to oil up the fingertip) and then press it gently to the center of the microscope slide. Place this slide on the table face up.
Now have both friends oil up their fingertips using their foreheads or side of their nose, and touch the center of a slide (one friend per slide).
Put on your goggles and gloves, and do NOT inhale the dust! Sprinkle a small amount of graphite powder into a disposable paper cup (just enough to cover the bottom of the cup).
Dip the brush into the cup and lightly dist the center area of a microscope slide and twirl the brush to make a thin coating of graphite on the surface of the slide. As the print shows through, remove the excess by lightly brushing it away in the direction of the ridge lines.
Use the tape to lift the print from the slide to your card. Remember to hold only the edge of the tape!
Use your magnifying lens to match the prints and be able to tell which friend touched the first slide.
Now let your friends handle different objects, like a water glass, newspaper, magazine picture, construction paper, and other materials. Make sure they know which finger is making the print so you can match it to their original print from the slide. Practice lifting prints from different objects and transferring them to the index / fingerprint card.
What if you use cocoa powder instead of graphite?

There are a number of ways to make invisible prints visible, depending on what the material is made out of. For porous materials like paper, rubber, cardboard or wood, you can use iodine fuming or ninhydrin to chemically react with the fingerprint and make the print visible (more on that in Part 5 below). For non-porous materials like glass or tile, you can use graphite powder, talcum powder (when you need the print to show up white instead of black), or cyanoacrylate fuming (refer to Part 4). The difference in the two types of materials arises because the porous materials can absorb liquid whereas non-porous are sealed , solid and smooth.

You can not leave fingerprints if you create a barrier between the surface you’re touching and your fingertips. You can either wear gloves, or use hand cream like DEB Hand Barrier which makes a second skin over your hand.

Experiment Part 3: Making an Artificial Fingerprint

Make a good fingerprint in the clay. Make sure you see ridgelines.
Cut off the tip of the silicone using scissors.
Apply a layer of caulk over the fingerprint, extending 1/2″ margin on all sides around the fingerprint. Press the caulk down with the tip to make sure you don’t have any air bubbles.
Let dry 24 hours.
Lift the caulk from the print using a fingernail and a lot of patience. Try not to bend, stretch, or deform the caulk print as you separate it from the clay.
Use your magnifying glass to look at the ridges in the caulk print.
Find a clean microscope slide.
Rub your finger against your nose or forehead, and rub that finger onto the ridges of the caulk print (artificial finger) and press the caulk print ridge-side down onto the slide.
Using the procedures from above, apply graphite to make the print visible and then transfer the print using tape to your card.
Compare the print from the artificial print with the original fingerprint. What do you notice?

Experiment Part 4: Superglue Reaction with Latent Fingerprints

Make a foil tray by bending up the edges of the square of foil. Place this in the bottom of the jar.
Attach the string to a black colored object using duct tape. The other end of the string is attached to the inside lid of the jar so that the black object hovers an inch or two above the foil tray.
Wipe the black object clean of all fingerprints.
Make a single, clear fingerprint on one side of the black object (rub your finger against your nose or forehead first).
Using gloves on your hands, place 20 drops of superglue in the tray. Don’t get this on your fingers!
Carefully lower the black object into the jar. Make sure it hovers above the tray. Screw the lid on tight.
Let it sit for 3 hours to develop the print.
When ready, unscrew the lid and remove the object and place it fingerprint-side-down on a photocopier and make a copy of the exposed print.
Roll up the superglue foil tray and throw in the trash. Be careful to handle this with your gloves on!
What other objects can you use for this fuming process?

Superglue contains a chemical called cyanoacrylate, which has fumes that react with the moisture in the fingerprint to make it visible.

TEACHER DEMO ONLY Experiment Part 5: Developing Latent Fingerprints with Iodine Crystals

Do NOT let kids do this experiment on their own. This is for adult / teacher demo purposes only as it involves handling iodine.

Never handled or worked with iodine? Do this experiment first.

After rubbing your finger on your forehead or nose, make a single, clear fingerprint on an index card.
Using foil, make a small tray (same procedure as Part 4 above) and place in the bottom of a glass jar.
Putting on your gloves and goggles, add about 10 iodine crystals to the tray. DO NOT INHALE FUMES OR TOUCH IODINE WITH YOUR BARE HANDS!
Suspend the index card with the fingerprint from the inside lid of the jar using string (same procedure as Part 4 above).
Lower the card into the jar and screw on the lid. Let this develop for 3-5 minutes. Look for a yellow fingerprint.
Open the jar. (Do you have your gloves on?) Remove the paper sample. Reseal the jar.
Look carefully at the exposed print. (Look quickly as this may fade.) Take a photocopy of this exposed print.
Open the jar. Place iodine crystals back in the original container and dispose of the foil in the trash.

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Rear View Spy Glasses

Wednesday April 15, 2015

You can see what’s behind you with these easy to make rear-view spy glasses! Each lens has a mirror so you can see not only in front of you but also behind you. It’s quick to make and uses simple materials.

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Materials:
1 pair cheap sunglasses
2 small mosaic mirrors (like from a craft store)
Hot glue gun with glue sticks

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Laser Maze Detectors

Wednesday April 15, 2015

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.

Trip Wire Burglar Alarm

Wednesday April 15, 2015

Burglar alarms not only protect your stuff, they put the intruder into a panic while they attempt to disarm the triggered noisemaker. Our burglar alarms are basically switches which utilize the circuitry from Basic Circuits and clever tricks in conductivity.

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Spotting Counterfeits

Wednesday April 15, 2015

Can you spot a fake $10 from the real thing? It’s getting harder these days, but you can still do it using a microscope.

US dollar bills are make of a mix of cotton and linen, which is why they don’t fall apart when you leave them in your pants pocket and they go through the water. They also have trace amounts of iron embedded in them, so they flex slightly toward a strong magnet. Can you find the owl on the dollar bill?

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Newer US five dollar bills have a watermark. If you hold it up to the light, you’ll see another image appear that wasn’t there before.

Older fives have the names of 26 states written along the top of the building on the backside of the bill.

Five dollar bills also have strange borders on the front of the bill:

Fives also have microtexting printed right next to the name “Lincoln”:

Newer US ten dollar bills have an interesting mark. Look with your microscope at the bottom left corner at the “10”. Do you see how the lines inside are actually words?

The tens also have a unique color and loop patterns in the bottom right corner.

There’s also microtexting just above the name “Hamilton” on the front of the bill.

US twenty dollar bills have many different things you can spot with a microscope: the first is on the back of the sill, you’ll find a lot of little 20’s as watermarks scattered around the bill:

Microtexting on the twenty looks like this:

But what if you don’t have a microscope? Did you know you can create a compound microscope using just two hand held magnifiers? It’s all in how you use them to bend the light. This video below covers the fundamental basics of how two double-convex lenses can be used to make objects appear larger when right up close.

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Listening with Lasers

Wednesday April 15, 2015

Did you know that when you talk inside a house, the windows vibrate very slightly from your voice? If you stand outside the house and aim a laser beam at the window, you can pick up the vibrations in the window and actually hear the conversation inside the house.

First, I’ll show you how to build your own space-age laser communicator, then you can work on your spy device. The first thing we’re going to do is take the music from your iPOD (or stereo, or MP3 player) and transmit it on a laser beam to a detector on the other side. The detector has a earphone attached, so someone else can listen to the music from your laser. Weird, huh?

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Chemical Analysis

Wednesday April 15, 2015

If you find a white powder at the scene of a crime, how can you tell if it’s flour or something more dangerous? A detective uses a chemical lab to determine what the substance is. One of the things that scientists look for is pH, which is a measure of how acidic or basic the powder is based on either a color change or how much a substance reacts with baking soda.

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Acids are sour tasting (like a lemon), bases are bitter (like unsweetened cocoa powder). Substances in the middle are more neutral, like water. Scientists use the pH (power of hydrogen, or potential hydrogen) scale to measure how acidic or basic something is. Hydrochloric acid registers at a 1, sodium hydroxide (drain cleaner) is a 14. Water is about a 7. pH levels tell you how acidic or alkaline (basic) something is, like dirt. If your soil is too acidic, your plants won’t attract enough hydrogen, and too alkaline attracts too many hydrogen ions. The right balance is usually somewhere in the middle (called ‘pH neutral’). Some plants change color depending on the level of acidity in the soil – hydrangeas turn pink in acidic soil and blue in alkaline soil.

There are many different kinds of acids: citric acid (in a lemon), tartaric acid (in white wine), malic acid (in apples), acetic acid (in vinegar), and phosphoric acid (in cola drinks). The battery acid in your car is a particularly nasty acid called sulfuric acid that will eat through your skin and bones. Hydrochloric acid is found in your stomach to help digest food, and nitric acid is used to make dyes in fabrics as well as fertilizer compounds.

In this lab, you have several mystery powders as well as several clear liquids to identify. Set up the liquids along the length of the table and the powders along the width so you can keep track of which ones give you a reaction and of which type.

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Cryptography

Wednesday April 15, 2015

Cryptography is the writing and decoding of secret messages, called ciphers. Now for governments these secret ciphers are a matter of national security. They hire special cryptanalysts who work on these ciphers using cryptanalysis. The secret is, solving substitution ciphers can be pretty entertaining! Ciphers are published daily in newspapers everywhere. If you practice encoding and decoding ciphers, you too can become a really great cryptanalyst.

UV Wavelengths

Wednesday April 15, 2015

This is a super fun lab! First, we’re going to learn about what florescence is, then we’re going to shut off all the lights in the house and go for a black light treasure hunt.

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The reason stuff glows is that fluorescent objects absorb the UV light and then spit it back almost instantaneously. Some of that energy gets lost during that process, and that changes the wavelength of the light, which makes this light visible and causes the material to appear to ‘glow’.

Here are some things that glow: white paper (although paper made pre-1950 doesn’t, which is how investigators tell the difference between originals and fakes), club soda or tonic water (it’s the quinine that glows blue), body fluids (yes, blood, urine, and more are all fluorescent), Vitamins (Vitamin A, B, B-12 (crush and dissolve in vinegar first), thiamine, niacin, and riboflavin are strongly fluorescent), chlorophyll (grind spinach in a small amount of alcohol (vodka) and pour it through a coffee filter to get the extract (keep the solids in the filter, not the liquid)), antifreeze, laundry detergents, tooth whiteners, postage stamps, driver’s license, jellyfish, and certain rocks (fluorite, calcite, gypsum, ruby, talc, opal, agate, quartz, amber) and the Hope Diamond (which is blue in regular light, but glows red).

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Spectroscopy (Chemical Analysis)

Wednesday April 15, 2015

This experiment is for advanced students. There are many different elements inside of a star. But they are so far away that we can’t get close enough to study them… or can we? By studying the special light signature (called “spectral lines”) astronomers can figure out not only which element, but also the approximate temperature and density of the element within the star, in addition to getting an idea of what the magnetic fields look like, which tells us about stellar wing and what the planets might be doing around the star, or if there might be another companion star.

Spectroscopy is a very complicated science, so let’s get started by actually doing it, and we’ll figure out what’s going on along the way.

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Materials:

spectral analysis kit
matches and alcohol burner or candle with adult help
safety goggles and gloves

If you are making your own spectrometer, you can make a simple spectrometer or the more advanced calibrated spectrometer.

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Wireless Transmitter

Wednesday April 15, 2015

This project is for advanced students. Make sure you’ve completed the Police Siren project first!

This is a really cool one. You’re actually going to build a miniature radio station. You can broadcast your voice or music to a regular FM radio. It just has a very short range (about 100 feet, or 30 meters).

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Voice Prints

Wednesday April 15, 2015

Every voice has a unique pattern to it just like fingerprints, and scientists can see this pattern as wavy lines and whorls. In this activity, you’ll be able to turn someone’s voice into a pattern of lines and view their voiceprint.

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Materials:

empty soup can
balloon
small mirror
tape
scissors
hot glue gun
laser or flashlight

You can use this device to identify a recorded voice or a live voice. Detectives use voiceprints to compare and identify a suspect by having the suspect say common words such as a, and, I, is, it, on the, to, we and you and then they compare the recording to find a match.

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Splitting Hairs and Fiber Analysis

Wednesday April 15, 2015

If you have access to a microscope, then this lab is fun and easy to do. If you’re in the market for a microscope, you can view our microscope recommendations here. If you’ve got a microscope but just haven’t used it for awhile (or never), then look over the experiments here first to get you started. Cloth fibers, wool, human hair, salt, and sugar all look really different under a microscope. It’s especially fun to mix up salt and sugar first, and then look at it under the scope to see if you can tell the difference.

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Pull fibers from a fabric. If it’s super-curly, use a bit of tape at either end, stretching it along the length of the slide. Keep the tape near the ends so it doesn’t come into your field of view when you look through the microscope
Lower the stage to the lowest setting and rotate the nose piece to the lowest magnification power.
Place the slide on the stage in your clips.
Focus the hair by looking through the eyepiece and slowly turning the coarse adjustment knob. When you’re close to focus, switch to the fine adjustment knob until it pops into sharp view.
When you’re done, lower the stage all the way and insert a new slide… and repeat.
Find at least six things to look at from six different fabrics. Try cotton, wool, synthetic, nylon, rayon, etc.

After viewing the fiber specimens, you can bring them close to a lit candle and adult help for a flame test. Different fibers burn differently: some will continue to glow, smoke, or burn after taken from the flame, some fibers burn more quickly than others. Some fibers curl, others melt, and some don’t even catch fire at all.

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Chromotography

Wednesday April 15, 2015

If you look carefully at color images inside of books with a magnifying glass or a microscope, you’ll find there are only four colors that make up all the different colors you see. We’re going to learn how to separate the color that makes up different color markers, which work the same was as the colored printed images in books.

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Materials:

markers
blotting paper, paper towel, or coffee filters
water bottle
scissors

The different chemicals in the ink travel at different speeds along the surface of the paper when mixed with water. This is used to separate substances into its components.

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Pressure Sensor

Wednesday April 15, 2015

By controlling how and when a circuit is triggered, you can easily turn a simple circuit into a burglar alarm – something that alerts you when something happens. By sensing light, movement, weight, liquids, even electric fields, you can trigger LEDs to light and buzzers to sound. Your room will never be the same.

Switches control the flow of electricity through a circuit. There are different kinds of switches. NC (normally closed) switches keep the current flowing until you engage the switch. The SPST and DPDT switches are NO (normally open) switches.

The pressure sensor we’re building is small, and it requires a fair amount of pressure to activate. Pressure is force (like weight) over a given area (like a footprint). If you weighed 200 pounds, and your footprint averaged 10” long and 2” wide, you’d exert about 5 psi (pounds per square inch) per foot.

However, if you walked around on stilts indeed of feet, and the ‘footprint’ of each stilt averaged 1” on each side, you’d now exert 100 psi per foot. Why such a difference?

The secret is in the area of the footprint. In our example, your foot is about 20 square inches, but the area of each stilt was only 1 square inch. Since you haven’t changed your weight, you’re still pushing down with 200 pounds, only in the second case, you’re pressing the same weight into a much smaller spot… and hence the pressure applied to the smaller area shoots up by a factor of 20.

So how do we use pressure in this experiment? When you squeeze the foam, the light bulb lights up! It’s ideal for under a doormat or carpet rug where lots of weight will trigger it.

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Here’s what you need:

thin sponge or foam square (about 1″ square)
AA battery case
2 AA batteries
3 alligator clip wires
2 large paper clips
scissors
aluminum foil
buzzer or LED

Download Student Worksheet & Exercises

Troubleshooting: There are a few problem areas to watch out for when building this sensor. First, make sure the hole in your foam is big enough to stick a finger (or thumb) easily through. The foam keeps the foil apart until stepped on, then it squishes together to allow the foil to make contact through the hole.

The second potential problem is if the switch doesn’t turn the buzzer off. If this happens, it means you’re bypassing the switch entirely and keeping the circuit in the constant ON position. Check the two foil squares – are they touching around the outside edges? Lastly, make sure your foam is the kind that pops back into shape when released. (Thin sponges can work in a pinch.)

What’s happening? You’ve made a switch, only this one is triggered by squeezing it. If you’re using the special black foam without the hole, it works because the foam conducts more electricity when squished together, and less when it’s at the normal shape.

First, the special black foam is conducting some (but not enough) electricity when you squeeze it. It’s just the nature of the black foam included with the materials kit. Second, when you squeeze it, you’re getting the two foil squares to touch through the hole, and this is what really does it for your LED. When you release it, the foil spreads apart again because they are on opposite sides of the foam square.

Bonus Idea: Stick just the sensor under a rug and run longer wires from the sensor to your room. When someone comes down the hallway, they’ll trigger the sensor and alert you before they get there!

Exercises

How does this sensor work?
What makes this an NO switch?
How can you use both the trip wire and the pressure sensor in the same circuit? Draw it out here:

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Invisible Ink

Wednesday April 15, 2015

This method of decoding messages uses special ink that is invisible until something is done to make them appear on the paper. There are hundreds of formulas to make these special inks and some formulas even have multiple ways to develop the ink. Some recipes involve special chemicals, but many invisible inks can be made using materials that you have in your home. Watch the video and I’ll share a few recipes and teach you more about this method.

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Cobalt chloride (CoCl₂) has a dramatic color change when combined with water, making it a great water indicator. A concentrated solution of cobalt chloride is red at room temperature, blue when heated, and pale-to-clear when frozen. The cobalt chloride we’re using is actually cobalt chloride hexahydrate, which means that each CoCl₂ molecule also has six water molecules (6H₂O) stuck to it.

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Robotics Competition

Thursday November 20, 2014

I was digging through some old video files and found this hour-long video of a robot competition I attended, and thought you might be interested to see how much robots have changed (or not?) since then!

If you’ll notice in the video below, there are no Arduinos, no VEX pieces… everything was handmade using basic electronics knowledge. In fact, the two robots that were communicating using laptops that were bolted right onto the robot was actually a really innovative idea!

This video was from an event about 20 years ago… was when I was still teaching engineering at the university, and just getting started teaching kids.

The hour-long version of the video was kind of long and tedious (it was just watching competition after competition), so I slimmed it down to just under two minutes so you could really get a taste for it. Hope you enjoy it!

Arduino Robotics

An “Arduino” is a micro-controller that really makes robotics a lot easier and fun to create. First designed in 2005 by an Italian company, these single boards were originally intended for students learning robotics.

The board consists of standardized connectors, which allow a whole host of interchangeable add-on modules (shields) to be used. It’s like the brains of a computer that you can add inputs (like sensors) and outputs connections (like motors) to.

Arduinos are not limited to student robotics. In fact, you’ll find them anywhere there’s automation, from telescope observatories to weather stations to smart home functions.

We’re going to learn how to transform an inexpensive Arduino board into a fully functioning autonomous robot with sensors, just like the one in the image above. This will take several steps, so watch the videos in order so you don’t miss a thing.

Click Here for Arduino Robotics

VEX IQ Robotics

The VEX IQ Robotics Competition for elementary and middle school students is open to teams of two or more kids who build a robot to compete in local competitions.

While it’s really exciting and fun, it’s easy to feel overwhelmed due to the open-endlessness, and that’s what we’re going to hep you with. Ready to get started?

Click for VEX IQ Robotics

Special Science Teleclass: Electricity

Monday October 13, 2014

This is a recording of a recent live teleclass I did with thousands of kids from all over the world. I’ve included it here so you can participate and learn, too!

We’re going to study electrons and static charge. Kids will build simple electrostatic motor to help them understand how like charges repel and opposites attract. After you’ve completed this teleclass, be sure to hop on over the teleclass in Robotics!

Electrons are strange and unusual little fellows. Strange things happen when too many or too few of the little fellows get together. Some things may be attracted to other things or some things may push other things away. Occasionally you may see a spark of light and sound. The light and sound may be quite small or may be as large as a bolt of lightning. When electrons gather, strange things happen. Those strange things are static electricity.

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Materials:

Balloon (7-9″, inflated with air, not helium)
AA battery case
2 AA batteries for your battery case (cheap dollar-store “heavy duty” type are perfect. Don’t use alkaline batteries if you can help it, because kids are going to short circuit their circuits, and the cheaper kind are safer in case they do.)
1-2 LEDs
Alligator wires
1.5-3V DC motor
3-6V buzzer

If you want to make the laser burglar alarm, then get these also:

OPTIONAL: CdS Photoresistor for the laser burglar alarm
OPTIONAL: 9V Battery for laser burglar alarm
OPTIONAL: Laser pointer (the cheap kind from the dollar store work great) or strong flashlight for the laser burglar alarm

If you want to make the first robotics projects then also get these:

OPTIONAL: block of foam (any kind will do that is at least 2″ on each side)
OPTIONAL: 10 (or more) wood skewers at least 4″ long
OPTIONAL: 1 wood clothespin
OPTIONAL: Hot glue and glue sticks (with adult help)

If you want to make the second robotics project then also get these:

OPTIONAL: Additional 3V DV motor (you need two for this project)
OPTIONAL: 6 large popsicle sticks (tongue depressor size)
OPTIONAL: Tack or other sharp object for poking holes
OPTIONAL: Hot glue and glue sticks (with adult help)

Key Concepts

The proton has a positive charge, the neutron has no charge (neutron, neutral get it?) and the electron has a negative charge. These charges repel and attract one another kind of like magnets repel or attract. Like charges repel (push away) one another and unlike charges attract one another. Generally things are neutrally charged. They aren’t very positive or negative, rather have a balance of both.

Things get charged when electrons move. Electrons are negatively charged particles. So if an object has more electrons than it usually does, that object would have a negative charge. If an object has less electrons than protons (positive charges), it would have a positive charge. How do electrons move? It turns out that electrons can be kind of loosey goosey.

Depending on the type of atom they are a part of, they are quite willing to jump ship and go somewhere else. The way to get them to jump ship is to rub things together. Like in our experiment we’re about to do…

What’s Going On?

In static electricity, electrons are negatively charged and they can move from one object to another. This movement of electrons can create a positive charge (if something has too few electrons) or a negative charge (if something has too many electrons). It turns out that electrons will also move around inside an object without necessarily leaving the object. When this happens the object is said to have a temporary charge.

When you rub a balloon on your head, the balloon is now filled up with extra electrons, and now has a negative charge. Opposite charges attract right? So, is the entire yardstick now an opposite charge from the balloon? No. In fact, the yardstick is not charged at all. It is neutral. So why did the balloon attract it?

The balloon is negatively charged. It created a temporary positive charge when it got close to the yardstick. As the balloon gets closer to the yardstick, it repels the electrons in the yardstick. The negatively charged electrons in the yardstick are repelled from the negatively charged electrons in the balloon.

Since the electrons are repelled, what is left behind? Positive charges. The section of yardstick that has had its electrons repelled is now left positively charged. The negatively charged balloon will now be attracted to the positively charged yardstick. The yardstick is temporarily charged because once you move the balloon away, the electrons will go back to where they were and there will no longer be a charge on that part of the yardstick.

This is why plastic wrap, Styrofoam packing popcorn, and socks right out of the dryer stick to things. All those things have charges and can create temporary charges on things they get close to.

Questions to Ask

Does the shape of the balloon matter? Does hair color matter?
What happens if you rub the balloon on other things, like a wool sweater?
If you position other people with charged balloons around the table, can you keep the yardstick going?
Can we see electrons?
How do you get rid of extra electrons?
Rub a balloon on your head, and then lift it up about 5 inches. Why is the hair attracted to the balloon?
Why does the hair continue to stand on end after the balloon is taken away?
Why do you think the yardstick moved?
What other things are attracted or repelled the same way by the balloon? (Hint: try a ping pong ball.)

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Chemistry Experiments

Monday September 15, 2014

The summer chemistry section is full of great experiments that are not only fun but also designed to hone your observational skills. Chemistry experiments really speak for themselves, much better than I can ever put into words. And I’m going to provide you with a lot of these experiments to help you develop your observing techniques. Are you ready?

Special Science Teleclass: Flying Machines

Sunday September 7, 2014

This is a recording of a recent live teleclass I did with thousands of kids from all over the world. I’ve included it here so you can participate and learn, too!

Soar, zoom, fly, twirl, and gyrate with these amazing hands-on classes which investigate the world of flight. Students created flying contraptions from paper airplanes and hangliders to kites! Topics we will cover include: air pressure, flight dynamics, and Bernoulli’s principle.

Materials:

5 sheets of 8.5×11” paper
2 index cards
2 straws
2 small paper clips
Scissors, tape
Optional: ping pong ball and a small funnel

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Key Concepts

While the kids are playing with the experiments see if you can get them to notice these important ideas. When they can explain these concepts back to you (in their own words or with demonstrations), you’ll know that they’ve mastered the lesson.

Air pressure is all around us. Air pushes downward and creates pressure on all things.
Air pressure changes all the time.
Higher pressure always pushes.
The faster air travels over a surface, the less time it has to push down on that surface and create pressure. Fast moving air creates low pressure regions. (Bernoulli’s Law).
The four fundamental forces on an airplane are lift, weight, thrust, and drag.

What’s Going On?

There’s air surrounding us everywhere, all at the same pressure of 14.7 pounds per square inch (psi). You feel the same force on your skin whether you’re on the ceiling or the floor, under the bed or in the shower.

An interesting thing happens when you change a pocket of air pressure – things start to move. This difference in pressure causes movement that creates winds, tornadoes, airplanes to fly, and some of the experiments we’re about to do together.

An important thing to remember is that higher pressure always pushes stuff around. While lower pressure does not “pull,” we think of higher pressure as a “push”. The higher pressure inside a balloon pushes outward and keeps the balloon in a round shape.

Weird stuff happens with fast-moving air particles. When air moves quickly, it doesn’t have time to push on a nearby surface, such as an airplane wing. The air just zooms by, barely having time to touch the surface, so not much air weight gets put on the surface. Less weight means less force on the area. You can think of “pressure” as force on a given area or surface. Therefore, a less or lower pressure region occurs wherever there is fast air movement.

There’s a reason airplane wings are rounded on top and flat on the bottom. The rounded top wing surface makes the air rush by faster than if it were flat. When you put your thumb over the end of a gardening hose, the water comes out faster when you decrease the size of the opening. The same thing happens to the air above the wing: the wind rushing by the wing has less space now that the wing is curved, so it zips over the wing faster, and creates a lower pressure area than the air at the bottom of the wing.

The Wright brothers figured how to keep an airplane stable in flight by trying out a new idea, watching it carefully, and changing only one thing at a time to improve it. One of their biggest problems was finding a method for generating enough speed to get off the ground. They also took an airfoil (a fancy word for “airplane wing”), turned it sideways, and rotated it around quickly to produce the first real propeller that could generate an efficient amount of thrust to fly an aircraft. Before the Wright brothers perfected the airfoil, people had been using the same “screw” design created by Archimedes in 250 BC. This twist in the propeller was such a superior design that modern propellers are only 5% more efficient than those created a hundred years ago by the two brilliant Wright brothers.

Questions to Ask

When you’ve worked through most of the experiments ask your kids these questions and see how they do:

Higher pressure does which? (a) pushes (b) pulls (c) decreases temperature (d) meows (e) causes winds, storms, and airplanes to fly
The tips on the edge of a paper airplane wing provide more lift by: (a) flapping a lot
(b) destroying wingtip vortices that kill lift (c) getting stuck in a tree more easily (d) decreasing speed
In the ping pong ball and funnel experiment, the ball stayed in the funnel was because: (a) you couldn’t blow hard enough (b) you glued it into the funnel (c) the ball had a hole in it (d) the fast blowing caused a low-pressure region around the ball, causing the surrounding atmospheric pressure to be a higher pressure, thus pushing the ball into the funnel
If your plane takes a nose dive, you should try (a) changing the elevators by pinching the edges (b) change the dihedral angle (c) change how you throw it (d) all of the above
What are the four forces that act on every airplane in flight?
Draw a quick sketch of your plane viewed from the front with a positive dihedral.
If you were designing your own “Flying Paper Machine Kit”, what would be inside the box?
What’s the one thing you need to remember about higher pressure?
What keep an airplane from falling?
Where is the low pressure area on an airplane wing?

Answers:

1 (a, e) 2 (b) 3 (d) 4 (d) 5 (lift, weight, thrust, drag) 8 (higher pressure pushes) 9 (lift) 10 (top surface)

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Special Science Teleclass: Rocketry & Spaceflight

Monday September 1, 2014

This is a recording of a recent live teleclass I did with thousands of kids from all over the world. I've included it here so you can participate and learn, too! Blast your imagination with this super-popular class on rocketry! Kids learn about fin design, hybrid and solid-state rocketry, and how rockets make it into space without falling out of orbit. This class is taught by a real live rocket scientist (me!). We'll launch rockets during the class, too! [am4show have='p8;p9;p11;p38;p95;' guest_error='Guest error message' user_error='User error message' ] Materials:

straw
paperclip
rubber band
index card
popsicle stick
scissors
masking tape
water
alka-seltzer tablets (generic brands work fine)
film canister or small container with tight-fitting lid
OPTIONAL: Small toy car

Below you will find an older version of the same teleclass. We are making a different experiment during class, so the materials you will need are a little different: Materials:

2L soda bottle
1/2" PVC pipe
duct tape
pen or pencil
index cards
sheets of paper
bicycle inner tube

Key Concepts

A rocket has a few parts different from an airplane. One of the main differences is the absence of wings. Rockets utilize fins, which help steer the rocket, while airplanes use wings to generate lift. Rocket fins are more like the rudder of an airplane than the wings. Another difference is the how rockets get their speed. Airplanes generate thrust from a rotating blade, whereas rockets get their movement by squeezing down a high-energy gaseous flow and squeezing it out a tiny exit hole. If you've ever used a garden hose, you already know how to make the water stream out faster by placing your thumb over the end of the hose. You're decreasing the amount of area the water has to exit the hose, but there's still the same amount of water flowing out, so the water compensates by increasing its velocity. This is the secret to rocket nozzles - squeeze the flow down and out a small exit hole to increase velocity. The rockets we're about to build get their thrust by generating enough pressure and releasing that pressure very quickly. You will generate pressure both by pumping and by chemical reaction, which generates gaseous products.

What's Going On?

For every action, there is equal and opposite reaction. If flames shoot out of the rocket downwards, the rocket itself will soar upwards. It's the same thing if you blow up a balloon and let it go-the air inside the balloon goes to the left, and the balloon zips off to the right (at least, initially). Your rocket generates a high pressure by squeezing the air into a very small space and using Bernoulli's Principles in action! As you stomp on the rocket, the air pressure leaves the bottle pretty quickly, pushing the paper rocket out of the way as it zooms out of the tube. By narrowing the exit diameter, you allow the air to speed up as it exits, creating a higher launch for your rocket. You can modify your rocket body design. Add more fins, tilt the fins at a angle, or try no fins at all! You can add a more steeply slanted nose. You can cut the rocket body in half or make it twice as long. There's so many things you can test out, change, or modify with this simple activity! You can also add canards (glider-type wings) to either side of the rocket body right under the nose and turn it into a glider when it starts to fall back to Earth!

Questions to Ask

Does it matter how many fins you use?
What happens if there's an air leak in the system?
How can you make the rocket fly even higher? Name three different ways.
Is the center of pressure before or aft of the center of gravity on your rocket?
For stable flight, how many fins do you ideally need?
How can you make the rocket spin as it launches?

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Liquid Nitrogen

Tuesday August 5, 2014

As promised, here’s the Liquid Nitrogen Ice Cream Social video that was only available to a handful of participants at our live summer camp last week! This is probably one of the last times Dr. Tom Frey will be doing this presentation, so we didn’t want to miss the opportunity to record it and share it with you!

Dr. Tom Frey just retired as a chemistry professor at Cal Poly State University, where he taught courses (including how to make your own lab glassware) for 42 years. He’s not only a mentor of mine, but a close personal friend and I am happy to share his talent and passion for science with you through this special, one of a kind video.

I really hope you enjoy it!

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Let me know what you think!

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Super Simple Catapult

Monday June 30, 2014

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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Drawing Machine

Monday June 30, 2014

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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Marshmallow Launcher

Monday June 30, 2014

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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Gravity Powered Go-Kart

Thursday May 22, 2014

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!). [am4show have='p8;p9;p100;' guest_error='Guest error message' user_error='User error message' ] Materials: Hardware Bits and Pieces:

- 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

Wood:

- 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)

Tools:

- 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

Make sure you wear your HELMET and get someone to help you with the power tools!

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. [/am4show]

Exploring Fluorescence using a Laser

Thursday May 22, 2014

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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Forensic Science

Sunday April 20, 2014

As a kid, I absolutely loved Encyclopedia Brown and Sherlock Holmes. What I really loved most about them was the science behind how they caught the bad guy… and now I’m going to share with you the basics of crime scene investigation in this section on forensic science.

Forensic science is a lot like engineering… it’s a place where you get to use stuff you’ve learned in other fields and apply it to the real world. With forensics, you get to use biology when you identify blood, DNA and diatoms; chemistry when you’re identifying unknown powders and poisons; physics when you’re looking at shattered glass, bullets, and explosions; and earth science with you’re looking at soil evidence.

The basic principle that forensics is based on is that someone either brought something to the crime scene or left something behind, which is called trace evidence. Trace because it’s usually really small, like a fiber of clothing, a hair, bits from a shoe, paint chips, wood splinters, or latent (invisible) fingerprints.

There’s a lot we’re going to cover! We’re going to several different fingerprinting methods, including how to lift fingerprints so you can study them as well as how to make artificial fingerprints using stuff from around the house. You’ll also learn about chromotography, which is how to separate black ink into its different colors so you can find the pen that actually wrote the mysterious letter.

We’re also going to learn how to do fiber flame tests to be able to help you identify which fibers are which so you can match it with what the suspect is wearing. Chemical analysis is also really important, and you’ll learn how to tell which powder is which using a matrix technique. We’ll also look at counterfeit money by making microscopes, fake documents in different wavelengths of light, and learn how handwriting tells you a lot about a person and how they think and feel.

In addition to collecting and analyzing evidence, we’re also going to learn how to secretly listen to conversations inside the house from the front yard, how to make laser burglar alarms to help you catch the bad guy, make rear-view spy glasses that let you see what’s going on behind you, write in different types of invisible ink, a wireless FM transmitter so you can transmit your voice to your allies without using walkie talkies, and learn how to make your own laser maze by building the home-made transistor detectors (these are the ones we use at Science Camp in the Laser Maze)!

There are over 20 videos to take you step by step into the world of evidence, analysis, investigation, and decoding mysteries! Are you ready?

Click here to go to the Forensic Science area!

Magnetic Tornadoes

Sunday September 1, 2013

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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Sundial

Sunday September 1, 2013

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 43^o 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 43^o. 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. 90^o 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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What’s Up in the Sky?

Sunday September 1, 2013

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 20^th 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 40^o north latitude and 90^o west longitude lines (which is Peoria, Ill.).
1. If you live near the standardized longitudes for Eastern Time (75^o), Central (90^o), Mountain (105^o) or Pacific (120^o), 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:
  1. For every degree west, add four minutes to the time you read off the chart.
  2. For every degree east, subtract four minutes from the time.
  3. For example, if you lived in Washington, D.C. (which is 77^o longitude), note that this is 2^o 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.
2. If your latitude isn’t 40^o north, then you need to adjust the rise and set times like this:
  1. If you live north of 40^o, 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.
  2. If you live south of 40^o, 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.
  3. 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.

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 Swinging System

Sunday September 1, 2013

Johannes Kepler, a German astronomer famous for his laws of planetary motion. Check out our Johannes Kepler facts page for more information.

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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Star Wobble

Sunday September 1, 2013

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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Eclipses and Transits

Sunday September 1, 2013

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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Meteorites

Sunday September 1, 2013

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:
1. 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.
1. 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.
2. 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.
3. 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.
4. 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.
5. 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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Solar Rotation

Sunday September 1, 2013

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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Sky in a Jar

Sunday September 1, 2013

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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Seasons

Sunday September 1, 2013

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:
1. 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.
2. 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.
3. 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:
1. Find the halfway point between the South Pole and the equator. Put one thermometer on this mark.
2. 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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Star Gazing

Sunday September 1, 2013

Telescopes and binoculars are pretty useless unless you know where to point them. I am going to show you some standard constellations and how to find them in the night sky, so you’ll never be lost again in the ocean of stars overhead. We’re going to learn how to go star gazing using planetarium software, and how to customize to your location in the world so you know what you’re looking at when you look up into the sky tonight!
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Materials: You’ll need to download and install Stellarium Planetarium Software before watching the video below. If you need a paper planetarium, try downloading this star wheel from Sky & Telescope here or try this simple star wheel here.

Click to download the student worksheet.

You’re about to locate several different celestial objects by first finding them in your planetarium software (or after assembling your star wheel).

UPDATE! There’s a complete STARGAZING set of lessons now available! Go here to find the new STARGAZING LESSONS!

If you haven’t already, customize your planetarium software to your location by entering in your location and elevation.
Now adjust the time so that it’s set to the time you’d like to star gaze tonight. What time will you star gaze tonight? Write this in your science notebook.
For folks in the Northern Hemisphere, find the Big Dipper. For Southern Hemisphere folks, find the Southern Cross (or the Crux, but it really looks like a big kite). These are one of the most recognizable patterns, and easy for beginners to find.
For Northerners, use the Big Dipper to locate Polaris, the North Star. The two stars at the edge of the dipper point straight to the North Star. (Refer to top image.)
For Southerners, use the Southern Cross to find the south pole of the sky (sometimes called the “south pole pit” since there’s no star there at the exact pole point of the southern sky). The longer bar in the cross points almost exactly toward the South Pole. (Refer to bottom image.)
Using the Search option, find the planets that will be visible tonight by typing in their name into the search window. Which ones will be visible for you tonight? Write this in your science notebook.
In Stellarium, click the “Search” icon, then the “Lists” tab, and select “Constellations”. Select two different constellations you’d like to find tonight that are visible to you, and record information about them on a piece of paper so you have it with you tonight. Include information about how you’ll find it (for example, what is it next to?)
When you’re ready, flip open your science notebook to the page with what you’re planning to look at, grab a a flashlight, pencil, and then go outside to log your observations, just like a real scientist!

Observing Tip: Try to observe when the moon is less than first quarter phase or more than three quarters (meaning that the moon is less than 50% illuminated). You don’t need any fancy viewing equipment, only your science notebook, and if you can do it, bring your planetarium software program with you outside to help you locate the objects. Start small, and find a couple of things on the first night. If you don’t figure it out the first time, try again the next night. I learned the northern sky by learning one new constellation every time I went star gazing, and pretty soon I had a lot of them that I could identify easily.

Note: This isn’t something that’s going to work by osmosis. You will have to go outside, figure out where to look, and find the object. Figure out what you’re looking for, and about where you can expect to find it, and practice and test yourself over and over until you can successfully find it every time. If you’re getting frustrated, it’s time to stop and have a sip of hot cocoa before you try again. This is supposed to be a fun treasure hunt, so make it enjoyable!

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Song of the Sun

Sunday September 1, 2013

Helioseismology is the study of wave oscillations in the Sun. By studying the waves, scientists can tell what’s going on inside the Sun. It’s like studying earthquakes to learn what’s going on inside the earth. The Sun is filled with sound, and studying these sound waves is currently the only way scientists can tell what’s going on inside, since the light we see from the Sun is just from the upper surface.

Molecules are vibrating back and forth at fairly high rates of speed, creating waves. Energy moves from place to place by waves. Sound energy moves by longitudinal waves (the waves that are like a slinky). The molecules vibrate back and forth, crashing into the molecules next to them, causing them to vibrate, and so on and so forth. All sounds come from vibrations.

Materials

Musical instruments: triangles, glass bottles that can be blown across, metal forks, tuning forks, recorders, jaw harps, harmonicas, etc. Whatever you have will work fine.

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Download Student Worksheet & Exercises

Your teacher will pull out a bin of musical instruments of various types.
Assign one student to be the noisemaker. The rest will listen with their eyes closed and record their observations.
Everyone shuts their eyes except for the noise maker.
The noisemaker selects an instrument and plays it once. Everyone else listens.
The noisemaker selects another instrument and plays it once. Everyone listens.
The noisemaker selects a third instrument and plays it once. Everyone listens.
The noisemaker selects one of the three instruments and plays it as it moves. For example, if you’re playing the triangle, you can hit it and spin it. Or hit it as you are walking past the closed-eye listeners. Sound changes when the object is moving, so make the sound they hear appear to be different somehow.
The noisemaker puts the instruments back and everyone opens their eyes and records their data in the table.
Switch roles and find a new noisemaker for the next trial. Repeat steps 2-8.

What’s Going On?

The Sun is like the biggest musical instrument you’ve ever seen. A piano has 88 keys, which means you can play 88 different musical notes. The Sun has 10 million.

To play a guitar, you pluck one of the six strings. To play the piano, you hit a key and sound comes out. To play the flute, you blow across a hole. Drums require smacking things together. So how do you play the Sun?

Waves are the way energy moves from place to place. Sound moves from a mouth to an ear by waves. Light moves from a light bulb to a book page to your eyes by waves. Waves are everywhere. As you sit there reading this, you are surrounded by radio waves, television waves, cell phone waves, light waves, sound waves and more. (If you happen to be reading this in a boat or a bathtub, you’re surrounded by water waves as well.) There are waves everywhere!

Do you remember where all waves come from? Vibrating particles. Waves come from vibrating particles and are made up of vibrating particles.

Here’s rule one when it comes to waves….the waves move, the particles don’t. The wave moves from place to place. The wave carries the energy from place to place. The particles however, stay put. Here are a couple of examples to keep in mind.

If you’ve ever seen a crowd of people do the “wave” in the stands of a sporting event you may have noticed that the people only “vibrated” up and down. They did not move along the wave. The wave, however, moved through the stands.

Another example would be a duck floating on a wavy lake. The duck is moving up and down (vibrating) just like the water particles but he is not moving with the waves. The waves move, but the particles don’t. When I talk to you, the vibrating air molecules that made the sound in my mouth do not travel across the room into your ears. (Which is especially handy if I’ve just eaten an onion sandwich!) The energy from my mouth is moved, by waves, across the room.

Convection starts the waves moving. You’ve seen convection when a hot pot of water bubbles up. You can even hear it when it starts to boil if you listen carefully. Just below the surface of the Sun, the energy that started deep in the core has bubbled up to the surface to make gigantic bubbles emerge that are bigger than the state of Alaska. It’s also a noisy process, and the sound waves stay trapped beneath the surface, making waves appear on the surface of the Sun. This makes the Sun’s surface look like it’s moving up and down.

Scientists use special cameras to watch the surface of the Sun wiggle and move, and they look for patterns so they can determine what’s going on down inside the Sun. Since the sound is inside the Sun under the part we can see, we use sound to discover what’s inside the Sun.

Have you ever heard the Sun? The video is an actual recording of the song of the Sun.

If you’ve ever been inside an unfurnished room, you’ve heard echoes indoors. Sound bounces all around the room, just like it does inside the surface of the Sun.

Can sound waves travel through space? No. Sound requires a medium to travel through, since it travels by vibrating molecules, and there aren’t enough molecules in space to do this with (there are a couple random ones floating around here and there, but way too far apart to be useful for sound waves).

If you have a slinky, take it out and stretch it out to its full length on the table or the ground, asking someone to help you hold one end. Now move the slinky quickly to the left and back again, and watch the wave travel down the length and return. Now move your end quickly up and then back down the table, making a longitudinal wave. When this wave finishes, take your end and shove it quickly toward your helper, then pull back again to make a compression wave. Point out to the student how when the wave returns, it’s an echo. That’s what happens inside the Sun when the sound waves hit the surface of the Sun. They don’t go through the surface, but get trapped beneath it as they echo off the inside surface of the Sun.

Exercises

What did you notice that is different about the sounds you heard?
How can you tell that two sounds are different that came from the same instrument? (Movement causes sound waves to sound different.)
What did you notice about your guesses? What kind of instruments were you more correct about?

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Moons of Jupiter

Sunday September 1, 2013

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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Star Charting

Sunday September 1, 2013

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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Cosmic Ray Detector

Thursday August 1, 2013

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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Telling Time by the Stars

Tuesday June 25, 2013

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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Phases of the Moon

Monday June 24, 2013

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 5^o. 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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Arduino Two Wheeled Robot (Getting Started)

Thursday June 13, 2013

Arduinos are not limited to student robotics. In fact, you’ll find them anywhere there’s automation, from telescope observatories to weather stations to smart home functions.

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In this video, we’ll go over what will be covered during the various 2 wheel robot build, the tools you’ll need to complete the build, and other important information.

To begin with, we’ll build the motor shield for the robot. Next, we’ll build the chassis for the robot and install the Arduino and the motor shield. Then, we’ll build the line sensor and install it into the robot. At this point we’ll install the Arduino IDE and begin testing the robots motors and the line sensor. And finally, we’ll build the PING sensor, install it into the robot, and then test the servo motor and the PING sensor to make sure they are working as they should.

To complete the robot build you’ll need the following tools (if you’ve completed other projects from Unit 14, you’ll probably have most of these already):

2 Wheeled Arduino Robot Kit. The circuit boards used to be available as a build-it-yourself-kit, but now it only comes pre-assembled. You’ll want to review the videos in detail first to get familiar with the parts you’ll need.

Here are the alternate links to get the most important parts:

2-wheel chassis from Jameco or DF Robot
Arduino UNO Microcontroller
Motor Drive Shield For Arduino

Tools:

Phillips Screwdriver
Wire Cutter
Wire stripper
Small pair of pliers
Soldering Iron
Solder
Digital multimeter
Jump wires
Standard USB cable to connect the Arduino to the your computer (A to B)
And possibly a drill and a 1/4^th inch drill bit. I had to use a drill to make one hole on the chassis larger, you may need to do this as well.
You’ll need to get a micro B USB cable to connect the Arduino to the your computer.

After you’ve built your robot, you can add these optional, additional items (these are not required for building the robot):

DSS-P05 Standard Servo (optional)
URM37 V5.0 Ultrasonic Sensor (optional)
Ultrasonic Mounting Bracket (optional)
Infrared Distance Sensor Bracket (optional)

I also want to point out a few things before we get started:

During the motor shield build, be sure to save the excess leads that you cut off. We’ll be using those during the line sensor build. ([Note: the kit is no longer available, so you will not be building the Motor Shield, but rather purchasing one presoldered.]
You may also need to get some additional straight pin strip header. Look for 0.100 inch or 2.54 mm.

Let’s get started!

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Motor Shield Build

Thursday June 13, 2013

In this video we’ll show you how to build the motor shield which is used to control the motors of the 2 wheel robot. We’ll also show you some tips and tricks for soldering that are useful skills for any soldering project.

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Chassis Build

Thursday June 13, 2013

Now it’s time to build the chassis. We will cover every aspect of the assembling the chassis and solve a few problem along the way.
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Line Sensor Build

Thursday June 13, 2013

Since the line sensor will be constructed using a generic prototyping PC board, a lot of issues are discovered and solved during the build. A number of design changes are covered in this video dealing mostly with simplifying the line sensor build itself, and solving a connection problem between the line sensor cable and the motor shield. Additional pin strip header will be used in this video to solve one problem.

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Arduino IDE and Motor Test

Thursday June 13, 2013

This video covers the installation of the Arduino IDE, driver for the Arduino Leonardo, Install sketch libraries for the robot, test the Arduino with a simple LED blinking program, and then test the motors and the line sensor to make sure they are working correctly.

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Ping Sensor Build

Thursday June 13, 2013

This video covers building up the PING sensor, installing it into the robot, and then testing both the servo motor and PING sensor to make sure they are working correctly.

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Measure your Hair Width with a Laser

Sunday April 21, 2013

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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Flying Over the Earth at Night

Friday August 24, 2012

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

Rail Fence Cipher

Tuesday July 31, 2012

In this video, I’ll show you how to use the Rail Fence Cipher. Before you start, say this three times fast: cryptanalysts use cryptanalysis to crack ciphers!

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Download Student Worksheet & Exercises

How did you like the Rail Fence Cipher? Pretty neat, right? Would you rather encode or decode a cipher? I think both parts are fun. But if you’re encoding, just make sure the decoder knows the correct formula to use!

Exercises

Write the cipher of the following message:

COME TOMORROW AT 2PM
HE HAS ARRIVED AT THE AIRPORT
HE IS CARRYING A BAG
THEY ARE HERE NOW
COME AT MY PLACE

Write the cipher of the following message (use a three row zigzag)

COME TOMORROW IN MY OFFICE
LEAVE THEM BEHIND
WE WILL BE THERE SOON
The cipher below was encoded using a two rows zigzag method with six letters in every row. Decode it.
IMOIG OACMN NW
The cipher below was encoded using a three rows zigzag method with four letters in every row. Decode it.
ICINA ONOMM GW

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Twisted Path Cipher

Tuesday July 31, 2012

In this video, I demonstrate a Twisted Path Cipher. It uses a matrix and a path in order to encode your message. The shape of the path you create within the matrix of a Twisted Path Cipher determines how difficult it will be to break the code. Watch the video to learn exactly how it works.

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Download Student Worksheet & Exercises”

What did you think of the Twisted Path Cipher? Remember that it will be easier to break your code if you use straight lines, so consider using some extra tricks to make it more difficult. For example, spirals, and zigzags are super hard to crack, and paths don’t have to be continuous! If you’re encoding, just make sure that the decoder knows the correct path shape (or shapes) to use!

Exercises

Given the following message, what would be the best size of the table to use?

COME TOMORROW
WE ARE WAITING AT THE BUS STATION
THE LETTER IS IN HIS BRIEFCASE
HE WILL COME LATE TODAY

Identify the type of path indicated in the diagrams below

Write the cipher of the following message using the path in #5 above.

I WILL LEAVE FOR UK TODAY
AM ON MY WAY TO THE SCENE
I WILL ATTEND THE OPENNING DAY
I WILL BE THERE AT 2

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Shift Cipher

Tuesday July 31, 2012

Shift ciphers were used by Julius Caesar in Roman times. The key is a number which tells you how many letters you’ll shift the alphabet. These are fairly simple to encode and decode. However, you have to be extra careful when encoding because mistakes can throw off the decoding process. Watch the video to see why it’s important to double check your work!

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Download Student Worksheet & Exercises

Do you see why it’s important to double check the encoding? This is a simple code, but it’s easy to shift and end up with a jumble when your message is decoded. So always check your cipher with a practice decoding prior to sharing it.

Exercises

Use the key shift number 4 on the letters of alphabet to code or decode the following:

Encode the following statement:

OUR SCHOOL WAS THE BEST
I WAS THE BEST IN MATHEMATICS
I AM THREE FEET TALL
OUR SCHOOL HAS GOOD TEACHERS
COME TO MY RESCUE

Decode the following:

SAWNA HAWRE JCXQZ
SDWQE OQDAM PAOQE KJXQZ
LHAWO AYKIA QKZWU
EWIKJ IUSWU
ODAEO WCKKZ OEJCA NMXQZ

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Date Shift Cipher

Tuesday July 31, 2012

The Date Shift cipher is a much harder code to break than, for example, the more simple Shift cipher. This is because the shift number varies from letter to letter, and also because it’s polyalphabetic (this means that a single number can represent multiple letters). I’ll explain it all in the video.

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Download Student Worksheet & Exercises

What do you think about the Date Shift cipher? The possibilities for numerical keys are endless. You can use the date you’re sending the message, birth dates, phone numbers, and more! Just remember to start decoding by writing the key numbers over the top of the encoded cipher. And always makes sure the decoder has the correct numerical key!

Exercises

Which kind of key is used in date-shift ciphers?
In which direction is the cipher shifted when decoding?
How do you describe a cipher where a specific alphabetical letter represents more than one letter?

What would be the date shift key codes for the following?

April 4^th 1998 (Don’t forget that the key needs six digits! Use “04” for the date.)
Jan. 28^th 2012
Nov. 30^th 2011

Encode the following:

COME TO MY HOME : March 16^th 1999
THEY HAVE JUST LEFT : June 1^st 2001

What are the original messages? (These messages were sent on July 16^th 1992)

GUBZC GOGNZ
MKFZV GAZTO GROZQ

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Pig Pen Cipher

Tuesday July 31, 2012

The Pig Pen cipher is of the most historically popular ciphers. It was used by Freemasons a century ago and also by Confederate soldiers during the Civil War. Since it’s so popular, it’s not a very good choice for top secret messages. Lots of people know how to use this one! It starts with shapes: tic-tac-toe grids and X shapes. I really like it because coded messages look like they’re written an entirely different language! Watch the video to learn how it works.

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Download Student Worksheet & Exercises

Isn’t this a fun one! To make the cipher a little harder to crack, arrange the encoded message in groups of five characters. As always, remember that your intended recipient needs the Pig Pen key in order to decode your message.

Exercises

What’s the difference between the second and the fourth pig pen?

Draw the following:

The third pig pen
The first pig pen

Using the following pig pen key, encode #4-7:

GO TO SCHOOL
COME BACK
I WILL SLEEP LATER
NORTHERN AMERICA

Using the pig pen key, decode the following messages:

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Polybius Checkerboard Cipher

Tuesday July 31, 2012

Polybius was an ancient Greek who first figured out a way to substitute different two-digit numbers for each letter. In the Polybius cipher we’ll use a 5×5 square grid with the columns and rows numbered. Take a look at the video and I’ll show you how it works.

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Download Student Worksheet & Exercises

To make the Polybius more difficult to crack, you can write the alphabet backwards or in an up and down pattern rather than left to right. Just be sure the decoder knows if you’ve used a different path or pattern to encode.

Exercises

Write the grid that is used to encode and decode messages in the Polybius Cipher. (Can you think up your own?)
Identify the codes representing the following letters using the grid from the example in the lesson: A, O and C.

Encode the following statements using the Polybius Cipher grid from the main lesson:

LET US LEAVE
I AM LEAVING
THEY WILL COME
SHE IS HERE

Decode the following messages using the Polybius Cipher grid from the main lesson.

32-35-35-31-11-45-45-23-15-45-11-12-32-15
24-45-24-44-23-24-14-14-15-34
23-15-43-15-24-44-45-23-15-41-11-41-15-43
32-35-35-31-11-45-33-55-12-35-35-31

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Cracking Ciphers

Tuesday July 31, 2012

Cryptograms are solved by making good guesses and testing them to see if the results make sense. Through a process of trial and error, you can usually figure out the answer. Knowing some facts about the English language can help you to solve a simple substitution cipher. For example, did you know that an E is the most commonly-used letter in the English alphabet? It’s also the most commonly-used letter to end a word. Watch the video below to learn some more tips and tricks to get you on the right track to being an expert cryptogram solver!

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Download Student Worksheet & Exercises

So, it helps to have a lot of words to work with so that you can begin to recognize patterns in the code. Here are some examples from the video:

single letter words will most likely be either A or I
the most frequent two-letter words in English are OF, TO, and IN
the most frequently used three-letter words are THE and AND
finally, the most frequently occurring four-letter word in English is THAT

Additional tips include the fact that Q is almost always followed by U, and that N often (but not always) follows a vowel. Finally, if two code symbols occur in a row, they could be a consonant combination such as LL, EE, SS, OO, TT, etc. The real trick to this is to try something, and then if it doesn’t work, go back and try something else. Get lots of practice by checking in newspapers and magazines for these popular puzzles. If you really like them, you can find puzzle books full of cryptograms. You’ll be an expert cipher solver in no time!

Exercises

What does it mean by “cracking a cipher?”
In there a difference between cracking and decoding a cipher?
What is very important that a person should know before beginning the cracking process?
What is the most common letter of alphabet that is usually at the end of a word?
What is the most common letter that is usually at the beginning of a word?
If you have a letter all by itself, what is it most likely to be?
What are two of the most common two character words in sentences?
What are two of the most common three character words in sentences?
What is the most common four character word in sentences?

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Playfair Cipher

Tuesday July 31, 2012

This is a super hard cipher to break. It’s encoded by taking pairs of letters and numbers from a matrix. There are three rules to follow.

If both letters are in the same row, then use the letters immediately to the right of each other. (Think of the rows as wrapping from the right end back around to that same row’s left end).
If both letters are in the same column, then use the letters immediately below them. If necessary, the bottom letter wraps back around to the top of the same row.
If the two letters or numbers are in different rows and in different columns, then each letter is replaced by the letter in the same row that’s also in the same column of the other letter. Basically, you find each intersection of the pair. Use the letter or number below the pair and then the one above the pair.

Play Fair sounds really complicated, but that also makes it a tough code to crack! Watch the video and I’ll explain it all for you.

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Download Student Worksheet & Exercises

Isn’t this cool? It makes a lot more sense when you see it in action, right? Remember: when decoding the Playfair cipher, you have to shift up instead of down and left instead of right. And it’s easy to make a mistake by encoding in the incorrect order. So always double check your cipher before sending it on to the recipient. Mistakes make messages much harder for the decoder to interpret!

Exercises

What is the name given to the following table?

A	H	M	V	L	3	Y	D
X	K	B	5	P	Z	E	O
N	7	W	U	F	T	6	J
G	R	2	Q	C	A	I	S

Use the table in 1 above to answer question 2 – 10.

What will be the cipher for the following?

KB
HR
AR
EU
COME TO SCHOOL
GO HOME THEN

Decode the following messages

73 3N SG YZ 6X
SG MN YK A7 JO HD
Why is it important the number of letters in the message to be encoded be even?

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Telephone Cipher

Tuesday July 31, 2012

Code machines – or cipher machines – can be used to encode and decode messages. One everyday example of a code machine that you can easily access is a telephone. Watch this video and I’ll show you how it works.

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Download Student Worksheet & Exercises

What do you think about the Telephone Code? Remember to get those slash codes just right in order to make decoding easier for the message receiver. (No pun intended!)

Exercises

Encode the following using the telephone keypad:

COME BACK
LEAVE TODAY
HE ARRIVED
THEY WENT
HE IS COMING
REVEAL
GO AHEAD

Decode the following ciphers

1 6 3 7 4 2 2
8 64 8 3 3 5 4 6 4 3 6 6
2 8 7 8 7 2 5 4 2

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Summer Astronomy Shop List

Thursday May 31, 2012

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!

Click here to print this page.

Materials

• aluminum foil
• ball, 12″ in diameter (a beach ball works well)
• balloons (4)
• black paper (like construction paper) or cardboard
• bowl
• cardboard
• CD case, old and empty (the clear, plastic kind)
• CDs (old ones, about 4)
• chalk
• clay
• flashlight
• glass jar (like a clean, empty jam jar)
• glitter or confetti
• golf ball or ping pong ball
• index cards (any size)
• magnet (any size, but the stronger you have the better it will work to detect meteorites)
• magnifying lenses, handheld (2)
• marble, shooter-size (big)
• marbles, 3 regular-size
• measuring tape (the longest one you have)
• metal ball (like a ball bearing) or a magnetic marble
• paper
• pencil
• pennies (10)
• peppercorns or similar size (3)
• protractor
• regular copy paper (any size)
• rocks (about ten the size of a quarter)
• sand or white sugar (1 tsp)
• sand paper
• saran wrap (or cut open a plastic shopping bag so it lays flat)
• scissors
• skewer or chopstick
• small bouncy balls (2 or 3)
• soda bottles, 2L clear plastic
• steel washer with a 3/8″ hole
• string
• tape
• tennis ball and/or basketball
• thumbtack
• vice grips or hacksaw
• wire coat hanger
• yardsticks or meter sticks (2)

Fun with a Handheld Van de Graff Generator

Sunday April 1, 2012

If you have a Fun Fly Stick, then pull it out and watch the video below. If not, don’t worry – you can do most of these experiments with a charged balloon (one that you’ve rubbed on your hair). Let’ play with a more static electricity experiments, including making things move, roll, spin, chime, light up, wiggle and more using static electricity!

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Materials:

sheet of paper
two empty, clean soup cans
aluminum foil
long straight pin
three film canisters (or M&M containers)
penny
sheet of paper
neon bulb
small styrofoam ball
fishing line or thread
chopstick
foam cup
dozen small aluminum pie tins
hot glue with glue sticks
Fun Fly Stick (also called “Wonder Fly Stick”)

This video show you how to get the most out of your Fun Fly Stick. If you don’t have a Fly Stick, simply use an inflated balloon that you’ve rubbed on your head. In the video, the Electrostatic Lab is mounted on a foam meat tray I found at the grocery store.

Download Student Worksheet & Exercises

The triboelectric series is a list that ranks different materials according to how they lose or gain electrons. Near the top of the list are materials that take on a positive charge, such as air, human skin, glass, rabbit fur, human hair, wool, silk, and aluminum. Near the bottom of the list are materials that take on a negative charge, such as amber, rubber balloons, copper, brass, gold, cellophane tape, Teflon, and silicone rubber.

When you turn on your Fun Fly Stick (or rub your head with a balloon), one end of the Fun Fly Stick takes on a positive charge and the other end holds the negative charge. When you rub your head with a balloon, the hair takes on a positive charge and the balloon takes on a negative charge.

When you scuff along the carpet, you build up a static charge (of electrons). Your socks insulate you from the ground, and the electrons can’t cross your sock-barrier and zip back into the ground. When you touch someone (or something grounded, like a metal faucet), the electrons jump from you and complete the circuit, sending the electrons from you to them (or it).

Exercises

What is common throughout all these experiments that make them work?
What makes the neon bulb light up? What else would work besides a neon bulb?
Does it matter how far apart the soup cans are?
Why does the foil ball go back and forth between the two cans?
Why do the pans take on the same charge as the Fly Stick?
When sticking a sheet of paper to the wall, does it matter how long you charge the paper for?
Draw a diagram to explain how the electrostatic motor works. Label each part and show where the charges are and how they make the rotor turn.

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Cartesian Diver

Sunday October 23, 2011

Rene Descartes (1596-1650) was a French scientist and mathematician who used this same experiment show people about buoyancy. By squeezing the bottle, the test tube (diver) sinks and when released, the test tube surfaces. You can add hooks, rocks, and more to your set up to make this into a buoyancy game!
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The test tube sinks because the when you squeeze the bottle, you increase the pressure of the water and this forces water up into the test tube, which then compresses the air inside the tube. When this happens, it adds enough mass to cause it to sink. Releasing the squeeze on the bottle means that you decrease the pressure and the water is forced back out of the tube.

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Ferrofluid

Friday July 1, 2011

A ferrofluid becomes strongly magnetized when placed in a magnetic field. This liquid is made up of very tiny (10 nanometers or less) particles coated with anti-clumping surfactants and then mixed with water (or solvents). These particles don’t “settle out” but rather remain suspended in the fluid.

The particles themselves are made up of either magnetite, hematite or iron-type substance.

Ferrofluids don’t stay magnetized when you remove the magnetic field, which makes them “super-paramagnets” rather than ferromagnets. Ferrofluids also lose their magnetic properties at and above their Curie temperature points.

Ferrofluids are what scientists call “colloidal suspensions”, which means that the substance has properties of both solid metal and liquid water (or oil), and it can change phase easily between the two. (We as show you this in the video below.) Because ferrofluids can change phases when a magnetic field is applied, you’ll find ferrofluids used as seals, lubricants, and many other engineering-related uses.

Here’s a video on toner cartridges and how to make your own homemade ferrofluid. It’s a bit longer than our usual video, but we thought you’d enjoy the extra content.

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Download Student Worksheet & Exercises

Engineering and scientists use ferrofluids to make a liquid seal in hard disks around the spinning disks to keep out dust and grit (hard drives must be kept exceptionally clean!). They do this by adding a layer of ferrofluid between the rotating shaft and magnets which surround the shaft.

You can also use ferrofluids to reduce friction, the way ice and water are used in ice skating rinks. If you coat a strong magnet with ferrofluid, you can get it to glide across a smooth surface like a hockey puck.

NASA uses ferrofluids in the flight instruments for spacecraft, also!

Each particle of ferrofluid is like a each grain or a micro-magnet, which not only interacts with magnetic fields, but also with light.

With loudspeakers, the large magnets that interacting with the coil often heat up. If we replace the magnet with ferrofluid (which is a liquid, remember!) it will actively conduct the heat away from the coil and cool it down because cold ferrofluid is more strongly attracted than hot, and thus the cooler fluid flows toward the coil, and the warmer fluid moves away from the coil.

Exercises

Is the ferrofluid a solid or a liquid?
Does the strength of a magnet matter?
What would happen if the magnet went over the rim of the cup?
Does the ferrofluid have a north and south pole?
What happens if you bring a compass near the ferrofluid?
Name three specific ways ferrofluid makes our lives easier. How might you use a ferrofluid if you were inventing something?

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Vitamin C Indicator

Thursday June 30, 2011

You’d be surprised at where vitamin C pops up in your kitchen – I know I was! I found it in my broccoli, butternut squash, sweet potatoes, swiss chard, spinach, carrots, kale, peas, leeks, tomatoes, guava, watermelon, grapefruit, pecans, raspberries, bell peppers, onion, papaya, pineapple, and pistachios!

Vitamin C is essential for humans and some animals (mostly primates), protecting the body from oxidative stress (involved in many diseases) and helping heal wounds. When humans don’t get enough vitamin C, they get sick with scurvy (bleeding from all mucus membranes, brown spots on the skin…), which is actually how scientists discovered vitamin C in the first place.

Plants and most animals actually make their own vitamin C by converting glucose (sugar).

Latest research (2008) discovered that the red blood cells in humans and primates more efficiently use vitamin C already in the body by recycling DHA. The neat part about t his discovery is that only humans and some primates have this ability – plants and most other animals do not.

Let’s find out how much of this vitamin is already in your home – are you ready?

There are two videos to watch – the first shows you how to make your own homemade indicator, and the second shows you how to use it.

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Materials:

cornstarch
water
old saucepan (just for chemistry)
disposable stirring stick or spoon
iodine
stove with adult help
foods to test (you’ll be throwing them away when you are done – don’t eat them!)

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Instant Ice

Thursday June 30, 2011

Supercooling a liquid is a really neat way of keeping the liquid a liquid below the freezing temperature. Normally, when you decrease the temperature of water below 32^oF, it turns into ice. But if you do it gently and slowly enough, it will stay a liquid, albeit a really cold one!

In nature, you’ll find supercooled water drops in freezing rain and also inside cumulus clouds. Pilots that fly through these clouds need to pay careful attention, as ice can instantly form on the instrument ports causing the instruments to fail. More dangerous is when it forms on the wings, changing the shape of the wing and causing the wing to stop producing lift. Most planes have de-icing capabilities, but the pilot still needs to turn it on.

We’re going to supercool water, and then disturb it to watch the crystals grow right before our eyes! While we’re only going to supercool it a couple of degrees, scientists can actually supercool water to below -43^oF!

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Materials:

water
glass
bowl
ice
salt

Download Student Worksheet & Exercises

Don’t mix up the idea of supercooling with “freezing point depression”. Supercooling is when you keep the solution a liquid below the freezing temperature (where it normally turns into a solid) without adding anything to the solution. “Freezing point depression” is when you lay salt on the roads to melt the snow – you are lowering the freezing point by adding something, so the solution has a lower freezing point than the pure solvent.

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Hot Ice Sculptures

Thursday June 30, 2011

Did you know that supercooled liquids need to heat up in order to freeze into a solid? It’s totally backwards, I know…but it’s true! Here’s the deal:

A supercooled liquid is a liquid that you slowly and carefully bring down the temperature below the normal freezing point and still have it be a liquid. We did this in our Instant Ice experiment.

Since the temperature is now below the freezing point, if you disturb the solution, it will need to heat up in order to go back up to the freezing point in order to turn into a solid.

When this happens, the solution gives off heat as it freezes. So instead of cold ice, you have hot ice. Weird, isn’t it?

Sodium acetate is a colorless salt used making rubber, dying clothing, and neutralizing sulfuric acid (the acid found in car batteries) spills. It’s also commonly available in heating packs, since the liquid-solid process is completely reversible – you can melt the solid back into a liquid and do this experiment over and over again!

The crystals melt at 136^oF (58^oC), so you can pop this in a saucepan of boiling water (wrap it in a towel first so you don’t melt the bag) for about 10 minutes to liquify the crystals.

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Materials:

Sodium Acetate
Disposable aluminum pie plate

Download Student Worksheet & Exercises

You have seen this stuff before – when you combined baking soda and vinegar in a cup, the white stuff at the bottom of the cup left over from the reaction is sodium acetate. (No white stuff? Then it’s mixed in solution with the water. If you heat the solution and boil off all the water, you’ll find white crystals in the bottom of your pan.) The bubbles released from the baking soda-vinegar reaction are carbon dioxide.

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Salty Eggs

Thursday June 30, 2011

Did you know that most people can’t crack an egg with only one hand without whacking it on something? The shell of an egg is quite strong! Try this over a sink and see if you can figure out the secret to cracking an egg in the palm of your hand…(Hint: the answer is below the video – check it out after you’ve tried it first!)

How can you tell if an egg is cooked or raw? Simply spin it on the counter and you’ll get a quick physics lesson in inertia…although you might not know it. A raw egg is all sloshy inside, and will spin slow and wobbly. A cooked egg is all one solid chunk, so it spins quickly. Remember the Chicken and the Clam experiment?

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Materials:

hard-boiled egg
glass
water
salt

Download Student Worksheet & Exercises
This experiment is all about density. Density is basically how tightly packed atoms are. Mathematically, density is mass divided by volume. In other words, it is how heavy something is, divided by how much space it takes up. If you think about atoms as marbles (which we know they’re not from the last lessons but it’s a useful model), then something is more dense if its marbles are jammed close together.

For example, take a golf ball and a ping pong ball. Both are about the same size or, in other words, take up the same volume. However, one is much heavier, has more mass, than the other. The golf ball has its atoms much more closely packed together than the ping pong ball and as such the golf ball is denser.

Here’s a riddle: Which is heavier, a pound of bricks or a pound of feathers? Well, they both weigh a pound so neither one is heavier! Now, take a look at it this way, which is denser, a pound of bricks or a pound of feathers? Aha! The pound of bricks is much denser since it takes up much less space. The bricks and the feathers weigh the same but the bricks take up a much smaller volume. The atoms in a brick are much more squooshed together then the atoms in the feathers.

Back to the experiment – have you ever noticed you how float a lot easier in the ocean than the lake? If so, then you already know how salt can affect the density of the water. Saltwater is more dense that regular water, and your body tissues contain water (among other things).

Did you know that thinner people are more dense than heavier people? For example, championship swimmers will sink and have to work harder to stay afloat, but the couch potato next door will float more easily in the water.
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Rubber Eggs

Thursday June 30, 2011

If you soak chicken bones in acetic acid (distilled vinegar), you’ll get rubbery bones that are soft and pliable as the vinegar reacts with the calcium in the bones. This happens with older folks when they lose more calcium than they can replace in their bones, and the bones become brittle and easier to break. Scientists have discovered calcium is replaced more quickly in bodies that exercise and eating calcium rich foods, like green vegetables.

This is actually two experiments in one – here’s what you need to do:

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Materials:

hard boiled egg
glass or clean jar
distilled white vinegar

Download Student Worksheet & Exercises

When you first plop the egg in the vinegar, do you notice the tiny bubbles? The acetic acid (distilled vinegar) reacts with the calcium carbonate in the eggshell, and you may even notice a color change over a couple of days.

How high does your egg bounce? Does it matter how long you leave it in the vinegar for?

The second part of this experiment is to try this again, but now use a raw egg (wash your hands after handling your egg due to salmonella!) You’ll get a difference result – the eggshell will become flexible, but don’t bounce them.

Exercises

Describe what the eggshell looked like before the reaction.
Describe the acetic acid
The product you witnessed in this chemical reaction was carbon dioxide, a colorless, odorless gas. How can you tell there really was a chemical reaction?
Why did the egg turn to “rubber?”

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Two-Wheeler Robot

Thursday June 30, 2011

If you’ve ever ridden a two-wheel bicycle, you know that you have to not only pedal to move forward, but also balance in order to stay upright while you move.

Two wheeler robots are difficult to make because they need to balance in addition to carry out commands. The balance is done autonomously, meaning that the robot must be programmed to figure out how to balance itself.

We’re going to skip this complicated step and instead use gravity to balance for us. While this makes the robot a lot smaller, it’s also a lot quicker and easier to build than the model in this image. Are you ready?

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Materials:

2 old CDs
popsicle stick
two tops from water bottles
2 battery packs that hold 2 AA batteries each
four AA batteries
two 3V motors
4 alligator clip leads
drill with drill bits
hot glue gun

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Robot Cable Car

Thursday June 30, 2011

A cable car transports people or things in a vehicle that uses a strong cable to pull at a steady speed. Also called aerial lift, aerial tramway, or gondola, these are different from the cable cars associated with San Francisco, which use buried cables to move the car up steep streets.

The world’s longest working cable car is in Sweden and covers 26 miles. Sweden used to operate a 60-mile cable car, but only a 8.2 miles (13.2 km) of it still works today, however this section is the longest passenger cable car in operation currently.

We’re going to make a durable cable car that can travel as long as you have string for it to move along! It’s really a cool and simple project, and you can add cups or berry baskets below to transport cargo. Here’s what you need to do:

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Materials:

6 popsicle sticks
AA battery case with 2 batteries
two 3VDC motors
tack
scissors
string
hot glue gun
glue stick for glue gun and also another one for use in the project itself (watch the video)
two alligator clip wires (four if your motor does not have wires comes out the end but tabs instead)

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Laser Microscope

Thursday June 30, 2011

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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Cool Milk Trick

Thursday June 30, 2011

Have you ever tried washing dishes without soap? It doesn’t work well, especially if there’s a lot of grease, fat, or oil on the dish!

The oils and fats are slippery and repel water, which makes them a great choice for lubration of bearing and wheels, but lousy for cleaning up after dinner.

So what’s inside soap that makes it clean off the dish? The soap molecule looks a lot like a snake, with a head and a tail. The long tail loves oil (hydrophobic) and the head loves water (hydrophilic). The hydrophilic end dissolves in water and the hydrophobic end wraps itself around fat and oil in the dirty water, cleaning it off your dishes.

Let’s do an experiment that will really make you appreciate soap and fat:

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Materials:

whole milk (if you have it – otherwise, use lowfat)
food dye
bowl
liquid soap

Download Student Worksheet & Exercises

While it may not look like it (or taste like it), milk is mostly water with minerals, proteins, and fat trapped inside. When you add a drop of soap, the hydrophobic end races around and grabs the fat and links up with other tail ends of soap molecules, forming the colors you see in the dish. The higher the fat content of your milk, the longer the show.
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Introduction to Creating a Homemade Weather Station

Wednesday June 29, 2011

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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Vitamin C Indicator	PVA Slime	What is Fire?
Instant Ice	Non-Messy Squishy Slime	Volcanoes
Hot Ice Sculptures	Corny Slime	Football Ice Cream
Salty Eggs	Bouncy Putty Slime	Acids & Bases
Rubber Eggs	Sewer Slime	Iodine Rainbow
Dinosaur Toothpaste	Glowing Slime	Simple Spectrometer and the more advanced Calibrated Spectrometer
Cool Milk Trick	Walk On Water	Colored Campfires and Rainbows
Bubble Experiments	Bouncy Ball	Ferro Fluid

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