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10000BC |
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constellations, lunar cycle, discovery of
planets? |
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calendar refinements for agriculture |
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counting schemes |
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months, year (in months, but uneven) |
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3000BC |
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# of days in year: ~360 |
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(360 degrees in circle) |
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heliacal rise of Sirius in Egypt -> 365 days |
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celestial pole |
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modern constellations (from Med. sailors) |
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solstices, equinoxes, Astrology |
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astronomical monuments (Stonehenge, Pyramids,
etc.) |
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astronomy strong in Mesopotamia/Europe, China,
Africa, Polynesia, Americas: everywhere! |
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500BC |
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Pythagorus - concentric celestial spheres for
Sun, Moon, planets - all bodies spherical (including Earth) |
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Philolaus - Earth goes around central fire (Sun) |
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350BC |
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Aristotle - Sun is further than Moon (slower
against stars), eclipses - Earth is round (shadow on Moon), going north
makes pole star rise |
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choose geocentric model |
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feels like it; no stellar parallax |
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300BC |
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Aristarchus - size of Sun and Moon relative to
Earth, relative distances (use of geometry to deduce them) |
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using geometrical reasoning D(sun)/D(moon)~20
, R(earth)/R(moon)~20 , R(sun)/R(earth)~7 |
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Sun is much bigger, so choose heliocentric
model (doesn't take hold, Aristotle wins) |
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Eratosthenes determines the true size of the
Earth |
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(and
gets it right) |
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using the day when the Sun |
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shines right down a well at |
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the solstice |
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150BC |
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Hipparcos - star catalog (850, position and
brightness) |
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- better estimates of size and distance of Moon |
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R(earth)/R(moon)~8/3, D(moon)~60R(earth),
D(sun) big |
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- precession of Earth's pole |
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-epicycles and deferent (used by Ptolmey) to
explain retrograde motion of planets |
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150AD |
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Ptolmey - worked out a full geometric geocentric
cosmology |
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- accounts for retrograde motion of planets |
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- predicts planetary positions |
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- 55 concentric cosmic spheres, all circular
motion |
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(size of Universe about 20000R(earth)) |
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Professor, engineer, scientist, writer,
“heretic” |
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One of the first to use experiment to deduce
physical laws |
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Laws of motion, velocity, acceleration, inertia,
pendulums, falling bodies |
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Brought telescopes to Astronomy |
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After initial skepticism, adopted Copernican
model because of empirical evidence in support |
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Notes