Robert Fineberg, age 12, of Portland, Maine, or his question:

What are cosmic rays?

Here is your chance to prove that there are visitors from outer space. You will need a simple cloud chamber for your experiment, one you can make yourself, The chamber will be a glass jar about five inches wide and five inches deep with a metal screw on lid. To make the cloud for the inside of the chamber you will need about a quart of rubbing alcohol, two pounds of dry ice, a large wad of absorbent cotton, a piece of black cloth to cover the top of the jar and a piece of cardboard to fit snugly into the bottom of the jar. You will. also need a glass tray to keep the dry ice under control and last, but not least, .you will need a flashlight to spot those visitors from space.

Choose a room that can be made quite dark. Put the dry ice into the glass tray without letting it touch your skin. Add enough alcohol to make a mush, Put the cotton into the bottom of the jar and press it down with the cardboard circle. Soak the cotton with more alcohol. Tie the black cloth over the top of the jar and screw on the lid. Now turn.the jar upside down and set i t on the dry ice mush.

Pull the shades and turn the flashlight on the top end of the jar, which is now upside down. In a few minutes the misty cloud will form. Keep watching and you will see tiny bright trails flash across the dark background, These trails are caused by cosmic rays, submicroscopic particles which plunge into our atmosphere from the far reaches of outer space. These starry. footsteps last but a moment.

What we see in the cloud chamber is actually stage two of the cosmic ray activity. The first stage begins way out among the distant stars. Each star is a nuclear furnace pouring forth various forms of energy in all directions.  

Some of this energy is believed to be in the form of streaming submicroscopic particles. These particles whip across space with almost the speed of light4 It is believed that they are attracted by magnetic fields and our earth is a giant magnet.

These particles are called the primary cosmic rays and they tend to be drawn from the equator towards the earths magnetic poles. Most of them are protons, atomic particles charged with positive electricity and they travel at terrific speeds. They strike atoms in the air on the way down. When a primary particle collides with an atom of oxygen or nitrogen, it loses speed. The atom of gas struck by the cosmic ray will be shattered into a number of high speed fragments.

These speeding fragments are the secondary cosmic rays you see in the cloud chamber. Traveling through the fine mist in the glass jar, they leave a heated trail which condenses ;the mist into drops of the finest dew. Secondary cosmic rays may be speeding protons or neutrons. Other atomic particles are also let loose in the collision. These particles may hit still more atoms or they may strike the ground. Finally their energy is all used up, but meantime, other visitors from space are filtering down from the top of the atmosphere.