If you think about it, the nucleus of an atom (proton and neutron) really have no reason to stick together. The neutron doesn’t have a charge, and the proton has a positive charge. And most nuclei have more than one proton, and positive-positive charges repel (think of trying to force two North sides of a magnet together). So what keeps the core together?

The strong force. Well, actually the residual strong force. This force is the glue that sticks the nucleus of an atom together, and is one of the strongest force we’ve found (on its own scale). This force binds the protons and neutrons together and is carried by tiny particles called pions. When you split apart these bonds, the energy has to go somewhere… which is why fission is such a powerful process (more on that later).

The fundamental strong force holds the quarks together inside the proton and neutron. Itty bitty particles called gluons hold the quarks together so the atom doesn’t fly apart. This force is extremely strong – much stronger than the electromagnetic force. This force is also known as the color force (there is not any color involved – that is just the way it was named.)

The electromagnetic force keeps the electrons from flying away from the nucleus. When a plus (the nucleus) and minus (the electron) charge get close together, tiny particles called photons pull the two together.

What is Radiation?

Radiation is energy or parts of atoms that are given off. We measure radiation with a geiger counter, which has a tube of gas inside that every time it gets hit by radiation, it gives off a little electrical charge.

[am4show have=’p8;p9;p17;p44;’ guest_error=’Guest error message’ user_error=’User error message’ ] In the 20th century, scientists figured out that the core of an atom can break apart or join together with others. If you split an atom (called fission), you get smaller parts and a whole lot of energy. When this happens in nature, it’s called radioactivity. Unstable atoms spontaneously break apart and release particles and energy.

Here’s a cool video that shows the fission chain reaction (you can do this also if you have a box, at least 25 mouse traps and 25-50 ping pong balls with adult help):

Fusion is taking place inside the sun. The sun is not on fire, like a campfire or stove. So where does it get its energy from? The fusion process smacks particles together, which results in a big release of energy. The core of the sun is about one million degrees Celsius, which the surface temperature is a mere 15,000 degrees Celsius. The fusion process in the sun takes two naked protons (also known as a hydrogen nuclei) and smacks them together in a special sequence that results in the formation of helium. This complicated reaction is called the proton-proton chain, and occurs in all stars burning hydrogen in their core.

Radioactivity can be dangerous, but it isn’t always dangerous. For example, your household smoke alarm emits alpha particles (the main detector uses alpha decay), brick and mortar building emit beta particles, and gamma particles come directly from the sun. In fact, people themselves emit beta particle radiation! When an atom of radioactive material decays, there are three types of radiation that it may emit: alpha, beta, and gamma. Generally speaking, most radioactive materials emit two, or all three types of radiation.

Alpha particles were named long before we ever knew what they were. An alpha particle are two protons and two neutrons stuck together (also known as helium nuclei). Beta particles are either electrons or positrons. Gamma particles, also called gamma rays, are actually electromagnetic radiation (photons) of very, very high frequency and energy – high enough to damage living tissue. Fortunately, gamma ray bursts are rare and usually not pointed in our direction.

Alpha particles are relatively slow and heavy. They have a low penetrating power, so you can stop them with just a sheet of paper. Alpha particles can not penetrate your skin. Due to the low penetrating power of Alpha particles, they are generally not a cause for concern, unless you ingest some material that emits Alpha radiation. For the most part, materials that emit Alpha particles, also emit some Beta or Gamma radiation.

Beta particles are fast and light. Beta particles have a medium penetrating power, but they are stopped by a thin sheet of aluminum (such as aluminum foil) or plastic. Beta particles can penetrate deeply into your skin.

Gamma rays have a high penetrating power. It takes a thick sheet of metal such as lead, or concrete to reduce them significantly. If you want to stop all gamma rays dead in their tracks, you’d need a sheet of lead 27 light-years thick. (Yikes!) Gamma rays penetrate your skin, and continue going right through your body.

The really unusual aspect of radiation is that the emission levels stays constant, no matter how hot or cold you make the material, or if you shove it into the deep vacuum of space or increase the pressure to bursting,  the rate of natural radioactive decay from radioactive materials will always remain the same. This is why materials of this type are used in Atomic Clocks.

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