Enter the Greek Philosophers

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GreekAstronomy.ppt
Enter the Greek Philosophers Philosopher Lover
of Wisdom
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Enter the Greek Philosophers
Anaximander (611 647 BC) Believed that the
sun, moon, and stars were made of fire seen
through holes in a moving dome in the sky.
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Enter the Greek Philosophers
Pythagoras (569 475 BC) Nature and natural
phenomena can be described mathematically, and is
natural laws are to be deduced by pure reasoning.
Pure mathematics provided glimpses of the realm
of the gods. Zeno (490 425 BC) Nature cannot
be interpreted mathematically. Proposed the
Achilles and the Tortoise paradox. Plato (427
347 BC) Strongly influenced by Pythagoras.
Denounced experiment, in favor of the use of pure
reasoning and thought.
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Enter the Greek Philosophers
Democritus (460 370 BC) Proposed that the
Milky Way was composed of many distant unresolved
stars. Also, there are a large number of worlds
which wander through space. These worlds were
formed by diffuse matter which exists in space.
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Enter the Greek Philosophers
Aristotle (384 - 322 B.C.) developed an early
model of the cosmos based on the concept of
uniform circular motion. To account for the
motions of the stars, sun, moon, and the five
known planets, his model used 55 spherical shells
each centered on the earth. These shells were
divided into two regions the realm of change
near the earth and the eternally unchanging
heavens. The realm of change consisted of spheres
of each of the four classical elements earth,
water, air, and fire. The heavens were made of an
unchangeable, transparent material called the
ether.
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Enter the Greek Philosophers
Aristarchus (310 - 230 B.C.) His measurements
determined that the sum was bigger than the
earth. Argued it sun was bigger, it would be
harder for it to move than the earth. Introduced
heliocentric (sun centered) model of the
universe. Explained phases of the moon. Very
little is known of his work.
Reference PHY250 website Powerpoints, Lunar
Phases and Eclipses
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Enter the Greek Philosophers
Hipparcus (165 - 127 B.C.) Accounted for
retrograde motion of planets by introducing
deferent and epicycle.
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The End of Greek Philosophy
Ptolemy (140 A.D.) Refined the astronomical
model by introducing the equant.
Basically, a smaller sphere, with its center at
center of the deferent, upon which the earth was
placed.