the heavenly vault, but solids; that the moon derives her light from
the sun, and that this fact explains her phases; that an eclipse of
the moon happens when the earth cuts off the sun's light from her. He
supposed the earth to be flat, and to float upon water. He determined
the ratio of the sun's diameter to its orbit, and apparently made out
the diameter correctly as half a degree. He left nothing in writing.

His successors, Anaximander (610-547 B.C.) and Anaximenes (550-475
B.C.), held absurd notions about the sun, moon, and stars, while
Heraclitus (540-500 B.C.) supposed that the stars were lighted each
night like lamps, and the sun each morning. Parmenides supposed the
earth to be a sphere.

Pythagoras (569-470 B.C.) visited Egypt to study science. He deduced
his system, in which the earth revolves in an orbit, from fantastic
first principles, of which the following are examples: "The circular
motion is the most perfect motion," "Fire is more worthy than earth,"
"Ten is the perfect number." He wrote nothing, but is supposed to have
said that the earth, moon, five planets, and fixed stars all revolve
round the sun, which itself revolves round an imaginary central fire
called the Antichthon. Copernicus in the sixteenth century claimed
Pythagoras as the founder of the system which he, Copernicus, revived.

Anaxagoras (born 499 B.C.) studied astronomy in Egypt. He explained
the return of the sun to the east each morning by its going under the
flat earth in the night. He held that in a solar eclipse the moon
hides the sun, and in a lunar eclipse the moon enters the earth's
shadow--both excellent opinions. But he entertained absurd ideas of
the vortical motion of the heavens whisking stones into the sky, there
to be ignited by the fiery firmament to form stars. He was prosecuted