No one would have believed in the last years of the nineteenth
century that this world was being watched keenly and closely by
intelligences greater than man’s and yet as mortal as his own; that as men
busied themselves about their various concerns they were scrutinised and
studied, perhaps almost as narrowly as a man with a microscope might
scrutinise the transient creatures that swarm and multiply in a drop of
water. With infinite complacency men went to and fro over this globe
about their little affairs, serene in their assurance of their empire over
matter. It is possible that the infusoria under the microscope do the same.
No one gave a thought to the older worlds of space as sources of human
danger, or thought of them only to dismiss the idea of life upon them as
impossible or improbable. It is curious to recall some of the mental habits
of those departed days. At most terrestrial men fancied there might be
other men upon Mars, perhaps inferior to themselves and ready to
welcome a missionary enterprise. Yet across the gulf of space, minds that
are to our minds as ours are to those of the beasts that perish, intellects vast
and cool and unsympathetic, regarded this earth with envious eyes, and
slowly and surely drew their plans against us. And early in the twentieth
century came the great disillusionment.
The planet Mars, I scarcely need remind the reader, revolves about the
sun at a mean distance of 140,000,000 miles, and the light and heat it
receives from the sun is barely half of that received by this world. It must
be, if the nebular hypothesis has any truth, older than our world; and long
before this earth ceased to be molten, life upon its surface must have
begun its course. The fact that it is scarcely one seventh of the volume of
the earth must have accelerated its cooling to the temperature at which life
could begin. It has air and water and all that is necessary for the support of
animated existence.