Radiation
The Earth's atmosphere serves another very important purpose in sustaining life: it filters most of the sun's ultraviolet (nonionizing) rays that can be harmful to the body, and it protects us from the even more dangerous ionizing radiation of space. While we may occasionally become sunburned after several hours outdoors at the beach or elsewhere, the atmosphere shields and protects us from the worst effects of the sun's radiation. It is true that, even on Earth, overexposure to the sun can and will occur without adequate additional protection from lotions or creams manufactured for that purpose. Skin cancers are a risk faced by everyone on Earth. However, can you imagine how much more dangerous the sun's radiation would be with no protection from the atmosphere at all? That is the situation in space, but protection against such nonionizing radiation is relatively simple. The real problem is created by the ionizing radiation of space.There are several different ways that scientists describe a dose of ionizing radiation and such a description depends on two things. First, a dose measurement depends on the amount of radiation present. The basic unit of measurement for the amount of radiation present is the roentgen. Second, a dose measurement depends on the medium the radiation is penetrating. For instance, is the medium in question a human being, a spacecraft, or a house here on Earth? The medium is the material receiving the radiation. Scientists usually describe radiation exposure to humans in units of rem (roentgen equivalent, man).
+ Humans in Space: Environmental Challenges (Back) + Hangman
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