05ch5History2

05ch5History2 - Ch 5: Early History of Astronomy...

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Ch 5: Early History of Astronomy Constellation Pegasus Planetary motion Ancient understanding of the Universe (motion of planets) Geocentric model most popular 1400 years until… Beginnings of Modern Science (in time order): Copernicus (revived heliocentric model) Tycho (best observations prior to telescopes) Kepler (3 Laws of Planetary motion, ellipses) Galileo (first telescopic observations) Newton (3 Laws of Motion, gravity explains Kepler’s Laws)
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Constellation Pegasus Right Ascension: 22 hours Declination: 20 degrees Best seen in Sept 11pm, Oct at 9:00 PM, Nov at 7pm. Q: Why 2hours later per month? http://www.allthesky.com/con for photos, including that on top.
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Scale Drawing of Inner Solar System http://www-astro.phast.umass.edu/courseware/java/planets/planets.html this will show planets moving, if you can run java. Inclination 90 deg is the view from N Ecliptic pole http://seds.lpl.arizona.edu/nineplanets/nineplanets/nineplanets.html Planets orbit sun on elliptical orbits. All except Mercury, Mars and Pluto are extremely close to circles. All planets move in prograde direction = anti- clockwise seen from far above the Earth’s N Pole.
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Morning and Evening “Stars” Mercury and Venus always near the Sun in the sky. set after the sun in the evening, or rise before it in the morning. Venus is at most 47 deg from sun. Mercury 28 degrees.
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Prograde and Retrograde Motion Most objects in the solar system orbit and spin in a prograde direction: anti- clockwise seen from the Northern hemisphere. The occasional real retrograde motion in a clockwise direction – either orbit or spin – is likely due to a major collisions.
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Apparent Retrograde Motion The outer planets appear to go backwards relative to the stars every time the Earth (4,5,6) passes between them and the sun. The inner planets also appear go retrograde sometimes. Earth moves around the Sun faster than they do. They appear to move “backwards” in the sky when the Earth overtakes them. Hard to explain the if Earth is not moving. The “S” shape is due to the fact that the orbits are slightly inclined (not in the same plane).
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Only Pluto has a large Inclination Inclinations (tilts) to the ecliptic are small, except Pluto 17 degrees, Mercury 7 deg, Venus 3 deg, Saturn 2 deg, Mars 1.8 deg… Appendix A3 .
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Ancient Astronomy around the World
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Historical Astronomy 10000BC-3000BC 10000BC constellations, lunar cycle, planets move? calendar refinements for agriculture counting schemes months, year (in months, but uneven) 3000BC Knew about 360 days in year 360 degrees in circle) Time between when Sirius rises in exactly the same place at the same time of night is > 365 days celestial pole constellations solstices, equinoxes, Astrology astronomically aligned monuments (Stonehenge, Pyramids, etc.) astronomy seen in Mesopotamia/Europe, China, Africa, Polynesia, Americas
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This note was uploaded on 02/17/2009 for the course PHYS 7 taught by Professor Staff during the Winter '08 term at UCSD.

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05ch5History2 - Ch 5: Early History of Astronomy...

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