What more hopeless problem to one confined to earth
than that of determining their varying distances, their motions,
and their physical constitution? Everything on earth we can handle
and investigate. But how investigate that which is ever beyond our
reach, on which we can never make an experiment? On certain
occasions we see the moon pass in front of the sun and hide it
from our eyes. To an observer a few miles away the sun was not
entirely hidden, for the shadow of the moon in a total eclipse is
rarely one hundred miles wide. On another continent no eclipse at
all may have been visible. Who shall take a map of the world and
mark upon it the line on which the moon's shadow will travel
during some eclipse a hundred years hence? Who shall map out the
orbits of the heavenly bodies as they are going to appear in a
hundred thousand years? How shall we ever know of what chemical
elements the sun and the stars are made? All this has been done,
but not by the intellect of any one man. The road to the stars has
been opened only by the efforts of many generations of
mathematicians and observers, each of whom began where his
predecessor had left off.
We have reached a stage where we know much of the heavenly
bodies.
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