There is nothing new under the sun, says the Bible. Nor is the sun
itself new, we might add. As long as life has existed on earth, it has
been exposed to radiation from the sun, so that life and radiation are
old acquaintances and have learned to live together.
We are accustomed to looking upon sunlight as something good, useful,
and desirable, and certainly we could not live long without it. The
energy of sunlight warms the earth, produces the winds that tend to
equalize earth’s temperatures, evaporates the oceans and produces rain
and fresh water. Most important of all, it supplies what is needed for
green plants to convert carbon dioxide and water into food and oxygen,
making it possible for all animal life (including ourselves) to live.
Yet sunlight has its dangers, too. Lizards avoid the direct rays of the
noonday sun on the desert, and we ourselves take precautions against
sunburn and sunstroke.
The same division into good and bad is to be found in connection with
other forms of radiation—forms of which mankind has only recently become
aware. Such radiations, produced by radioactivity in the soil and
reaching us from outer space, have also been with us from the beginning
of time. They are more energetic than sunlight, however, and can do more
damage, and because our senses do not detect them, we have not learned
to take precautions against them.
To be sure, energetic radiation is present in nature in only very small
amounts and is not, therefore, much of a danger. Man, however, has the
capacity of imitating nature. Long ago in dim prehistory, for instance,
he learned to manufacture a kind of sunlight by setting wood and other
fuels on fire. This involved a new kind of good and bad. A whole new
technology became possible, on the one hand, and, on the other, the
chance of death by burning was also possible. The good in this case far
outweighs the evil.
In our own twentieth century, mankind learned to produce energetic
radiation in concentrations far surpassing those we usually encounter in
nature. Again, a new technology is resulting and again there is the
possibility of death.
The balance in this second instance is less certainly in favor of the
good over the evil. To shift the balance clearly in favor of the good,
it is necessary for mankind to learn as much as possible about the new
dangers in order that we might minimize them and most effectively guard
against them.
To see the nature of the danger, let us begin by considering living
tissue itself—the living tissue that must withstand the radiation and
that can be damaged by it.