COSMIC PARTICLES

If you sit in a room with no radioactive materials present and switch on a radiation counter with the window of the tube closed, you’ll notice an occasional click from the device. Some of the particles come from the Earth; there are radioactive elements in the ground almost everywhere (usually in small quantities). Some of the radiation comes indirectly from space. Cosmic particles strike atoms in the atmosphere, and these atoms in turn eject other subatomic particles that arrive at the counter tube.
In the early 1900s, physicists noticed radiation apparently coming from space. They found that the strange background radiation increased in intensity when observations were made at high altitude; the radiation level decreased when observations were taken from underground or underwater. This space radiation has been called secondary cosmic radiation or secondary cosmic particles. The actual particles from space, called primary cosmic particles, usually do not penetrate far into the atmosphere before they collide with and break up the nuclei of atoms. To observe primary cosmic particles, it is necessary to ascend to great heights, and as with the UV and x-ray investigations, this was not possible until the advent of the space rocket.

While the radiation in the EM spectrum—the radio waves, IR, visible light, UV, x-rays, and gamma rays—consists of photons traveling at the speed of light, primary cosmic particles are comprised of matter traveling at almost, but not quite, the speed of light. At such high speeds, the protons, neutrons, and other heavy particles gain mass because of relativistic effects, and this renders them almost immune to the effects of the Earth’s magnetosphere. Such particles arriving in the upper atmosphere come to us in nearly perfect straight-line paths despite the magnetic field of our planet. By carefully observing the trails of the particles in a device called a cloud chamber aboard a low-orbiting space ship, it is possible to ascertain the direction from which they have come. Over time, cosmic-particle maps of the heavens can be generated and compared with maps at various EM wavelengths.