ed to the
heliocentric point of view were pointed out by Copernicus, in addition
to his greater work of constructing improved planetary tables on the
basis of his theory. But it must be admitted that he himself felt the
hypothesis of the motion of the earth to be a difficulty. Its acceptance
is by no means such an easy and childish matter as we are apt now to
regard it, and the hostility to it is not at all surprising. The human
race, after having ridiculed and resisted the truth for a long time, is
apt to end in accepting it so blindly and unimaginatively as to fail to
recognize the real achievement of its first propounders, or the
difficulties which they had to overcome. The majority of men at the
present day have grown accustomed to hear the motion of the earth spoken
of: their acceptance of it means nothing: the attitude of the paradoxer
who denies it is more intelligent.

It is not to be supposed that the idea of thus explaining some of the
phenomena of the heavens, especially the daily motion of the entire
firmament, by a diurnal rotation of the earth had not struck any one. It
was often at this time referred to as the Pythagorean theory, and it had
been taught, I believe, by Aristarchus. But it was new to the modern
world, and it had the great weight of Aristotle against it.
Consequently, for long after Copernicus, only a few leading spirits
could be found to support it, and the long-established venerable
Ptolemaic system continued to be taught in all Universities.

The main objections to the motion of the earth were such as the
following:--

1. The motion is unfelt and difficult to imagine.

That it is unfelt is due to its uniformity, and can be explained
mechanically. That it is difficult to imagine is and remains true,
but a most important lesson we have to learn is that difficulty of
conception is no valid argument against reality.

2. That the stars do not alter their relative positions according to
the season of the year, but the constellations preserve always the same
aspect precisely, even to careful measurement.

This is indeed a difficulty, and a great one. In June the earth is
184 million miles away from where it was in December: how can we
see precisely the same fixed stars? It is not possible, unless they
are at a practically infinite distance. That is the only answer
that can be given. It was the tentative answer given by Copernicus.
It is the