it. The sun, it was held, is but
a great mirror, which reflects the light from the central fire. Sun
and earth alike revolve about this great fire, each in its own orbit.
Between the earth and the central fire there was, curiously enough,
supposed to be an invisible earthlike body which was given the name
of Anticthon, or counter-earth. This body, itself revolving about the
central fire, was supposed to shut off the central light now and again
from the sun or from the moon, and thus to account for certain eclipses
for which the shadow of the earth did not seem responsible. It was,
perhaps, largely to account for such eclipses that the counter-earth
was invented. But it is supposed that there was another reason. The
Pythagoreans held that there is a peculiar sacredness in the number ten.
Just as the Babylonians of the early day and the Hegelian philosophers
of a more recent epoch saw a sacred connection between the number seven
and the number of planetary bodies, so the Pythagoreans thought that the
universe must be arranged in accordance with the number ten. Their count
of the heavenly bodies, including the sphere of the fixed stars, seemed
to show nine, and the counter-earth supplied the missing body.

The precise genesis and development of this idea cannot now be followed,
but that it was prevalent about the fifth century B.C. as a Pythagorean
doctrine cannot be questioned. Anaxagoras also is said to have taken
account of the hypothetical counter-earth in his explanation of
eclipses; though, as we have seen, he probably did not accept that
part of the doctrine which held the earth to be a sphere. The names
of Philolaus and Heraclides have been linked with certain of these
Pythagorean doctrines. Eudoxus, too, who, like the others, lived in Asia
Minor in the fourth century B.C., was held to have made special studies
of the heavenly spheres and perhaps to have taught that the earth moves.
So, too, Nicetas must be named among those whom rumor credited with
having taught that the world is in motion. In a word, the evidence, so
far as we can garner it from the remaining fragments, tends to show that
all along, from the time of the early Pythagoreans, there had been an
undercurrent of opinion in the philosophical world which questioned the
fixity of the earth; and it would seem that the school of thinkers who
tended to accept the revolutionary view centred in Asia Minor, not far
from the early home of the founder of the Pyth