We are apt to say
to ourselves: "The earth is one of a number of planets, all similarly
circumstanced; the earth is inhabited, why should not the others also be
inhabited?"
What has been learned of the unity in chemical constitution and
mechanical operation prevailing throughout the solar system, together
with the continually accumulating evidence of the common origin of its
various members, and the identity of the evolutionary processes that
have brought them into being, all tends to strengthen the _a priori_
hypothesis that life is a phenomenon general to the entire system, and
only absent where its essential and fundamental conditions, for special
and local, and perhaps temporary, reasons, do not exist.
If we look for life in the sun, for instance, while accepting the
prevalent conception of the sun as a center of intense thermal action,
we must abandon all our ideas of the physical organization of life
formed upon what we know of it from experimental evidence. We can not
imagine any form of life that has ever been presented to our senses as
existing in the sun.
But this is not generally true of the planets. Life, in our sense of it,
is a planetary, not a solar, phenomenon, and while we may find reasons
for believing that on some of the planets the conditions are such that
creatures organized like ourselves could not survive, yet we can not
positively say that every form of living organism must necessarily be
excluded from a world whose environment would be unsuited for us and our
contemporaries in terrestrial life.
Pages:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25