Chapter 5-3

Ionizing Radiation

close up photo of a spider and its glistening web
No flies here.
The spider "Arabella" spins a web on Skylab.
Beyond the protective blanket of the Earth's atmosphere, space is filled with radiation of all kinds: the light and heat from the Sun, radio waves from Jupiter, X-rays and gamma rays from the Sun and from energetic, poorly-understood objects beyond our solar system. This radiation not only spans the electromagnetic spectrum, but also includes atomic and subatomic particles of all dimensions and energies. Much of the radiation is similar to that which can be produced on Earth, using radar, cyclotrons, or radioactive materials. The biological effects of these radiations can be studied in great detail. Other space radiations, such as the highly energetic HZE atomic particles, or cosmic rays, are unique to space and can be duplicated only imprecisely and with the greatest difficulty on Earth.

Cosmic rays have been studied in great detail, using a variety of detectors carried into space. One very sensitive detector turned out to be the human eye. Cosmic rays apparently are the cause of the "light flashes", bright streaks seen by the astronauts when their eyes were closed. Some of the displays were striking. On one lunar trip, brilliant green flashes were seen, causing the astronauts to report, "It looks like St. Patrick's Day."

There is no doubt that such penetrating radiation can produce biological damage. It is not yet clear that this radiation is any barrier to our progress into space, but we will need to be protected against it. How the radiation causes damage, what the dangerous exposure times are, and what the possible protective measures may be are all subjects of in tense scrutiny.

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