Debt to Astronomy" is from The Chautauquan; and "An Astronomical
Friendship" from the Atlantic Monthly.

SIMON NEWCOMB. WASHINGTON, JUNE, 1906.




I

THE UNSOLVED PROBLEMS OF ASTRONOMY


The reader already knows what the solar system is: an immense
central body, the sun, with a number of planets revolving round it
at various distances. On one of these planets we dwell. Vast,
indeed, are the distances of the planets when measured by our
terrestrial standards. A cannon-ball fired from the earth to
celebrate the signing of the Declaration of Independence, and
continuing its course ever since with a velocity of eighteen
hundred feet per second, would not yet be half-way to the orbit of
Neptune, the outer planet. And yet the thousands of stars which
stud the heavens are at distances so much greater than that of
Neptune that our solar system is like a little colony, separated
from the rest of the universe by an ocean of void space almost
immeasurable in extent. The orbit of the earth round the sun is of
such size that a railway train running sixty miles an hour, with
never a stop, would take about three hundred and fifty years to
cross it. Represent this orbit by a lady's finger-ring. Then the
nearest fixed star will be about a mile and a half away; the next