this universe extend? What are the distances and arrangements of the
stars? Does the universe constitute a system? If so, can we comprehend
the plan on which this system is formed, of its beginning and of its
end? Has it bounds outside of which nothing exists but the black and
starless depths of infinity itself? Or are the stars we see simply such
members of an infinite collection as happen to be the nearest our
system? A few such questions as these we are perhaps beginning to
answer; but hundreds, thousands, perhaps even millions, of years may
elapse without our reaching a complete solution. Yet the astronomer
does not view them as Kantian antinomies, in the nature of things
insoluble, but as questions to which he may hopefully look for at least
a partial answer.

The problem of the distances of the stars is of peculiar interest in
connection with the Copernican system. The greatest objection to this
system, which must have been more clearly seen by astronomers
themselves than by any others, was found in the absence of any apparent
parallax of the stars. If the earth performed such an immeasurable
circle around the sun as Copernicus maintained, then, as it passed from
side to side of its orbit, the stars outside the solar system must
appear to have a corresponding motion in the other direction, and thus
to swing back and forth as the earth moved in one and the other
direction. The fact that not the slightest swing of that sort could be
seen was, from the time of Ptolemy, the basis on which the doctrine of
the earth's immobility rested. The difficulty was not grappled with by
Copernicus or his immediate successors. The idea that Nature would not
squander space by allowing immeasurable stretches of it to go unused
seems to have been one from which medieval thinkers could not entirely
break away. The consideration that there could be no need of any such
economy, because the supply was infinite, might have been theoretically
acknowledged, but was not practically felt. The fact is that
magnificent as was the conception of Copernicus, it was dwarfed by the
conception of stretches from star to star so vast that the whole orbit
of the earth was only a point in comparison.

An indication of the extent to which the difficulty thus arising was
felt is seen in the title of a book published by Horrebow, the Danish
astronomer, some two centuries ago. This industrious observer, one of
the first who used an instrument resembling our