71. Not so long ago it was assumed that the dangers man would meet in
space would be terrible, the main ones being radiation and. the danger of being
hit by meteors. It is perhaps worth remembering that less than two centuries
ago, the dangers of train travel seemed similarly terrible. A man would
certainly die, it was thought, if carried along at a Speed of 30 miles per
hour. There are two sorts of radiation man must fear in space.
The first is radiation from the sun, and this is particularly dangerous when the
sun is very active and explosions are occurring on its surface. The second, less
harmful form comes from the so-called Van Allen Belts. These are two areas of
radiation about 1 ,500 miles away from the earth. 72. Neither of these forms
of radiation are a danger to us on the earth, since we are protected by our
atmosphere. Specifically, it is that part of our atmosphere known as the
ozonosphere which protects us. This is a belt of the chemical ozone between 12
and 21 miles from the ground which absorbs all the radiation.
Once outside the atmosphere, however, man is no longer protected, and
radiation can be harmful in a number of ways. 73. A distinction must be drawn
between the short-and long-term effects of radiation. The former are merely
unpleasant, but just because an astronaut returning from a journey in space does
not seem to have been greatly harmed, we cannot assume that he is safe. The
long-term effects can be extremely serious, even leading to death.
One solution to the dangers of radiation is to protect the spaceship by
putting some kind of shield around it. This was in fact done on the Apollo
spaceships which landed on the moon. But this solution is not possible for
longer journeys—to Mars for example—because the shield would need to be very
large, and could not be carried. Another solution, not in fact possible at
present, would be to surround the spaceship with a magnetic field to deflect the
radiation. In all, we have to conclude that there is at present no complete
solution to the problem of radiation.