accepted by Copernicus, whose orthodoxy was sincere, and who protested against the view that
his theory contradicted the Bible.
There were genuine difficulties in the Copernican theory. The greatest of these was the absence of
stellar parallax. If the earth at any one point of its orbit is 186,000,000 miles from the point at
which it will be in six months, this ought to cause a shift in the apparent positions of the stars, just
as a ship at sea which is due north from one point of the coast will not be due north from another.
No parallax was observed, and Copernicus rightly inferred that the fixed stars must be very much
more remote than the sun. It was not till the nineteenth century that the technique of measurement
became sufficiently precise for stellar parallax to be observed, and then only in the case of a few
of the nearest stars.
Another difficulty arose as regards falling bodies. If the earth is continually rotating from west to
east, a body dropped from a height ought not to fall to a point vertically below its starting-point,
but to a point somewhat further west, since the earth will have slipped away a certain distance
during the time of the fall. To this difficulty the answer was found by Galileo's law of inertia, but
in the time of Copernicus no answer was forthcoming.
There is an interesting book by E. A. Burtt, called The Metaphisical Foundations of Modern
Physical Science ( 1925), which sets forth with much force the many unwarrantable assumptions
made by the men who founded modern science. He points out quite truly that there were in the
time of Copernicus no known facts which compelled the adoption of his system, and several
which militated against it. "Contemporary empiricists, had they lived in the sixteenth century,
would have been the first to scoff out of court the new philosophy of the universe." The general
purpose of the book is to discredit modern science by suggesting that its discoveries were lucky
accidents springing by chance from superstitions as gross as those of the Middle Ages. I think this
shows a misconception of the scientific attitude: it is not what the man of science believes that
distinguishes him, but how and why he believes it. His beliefs are tentative, not dogmatic; they are
based on evidence, not on authority or intuition. Copernicus was right to call his theory a
hypothesis; his opponents were wrong in thinking new hypotheses undesirable.
The men who founded modern science had two merits which are