NATS 2-3

NATS 2-3 - NATS February 3 Announcements Mid-term exam is...

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NATS February 3 Announcements: - Mid-term exam is on February 26 Johannes Kepler: 1600 - German astronomer, started as Tycho’s assistant o Didn’t like Tycho much, may even have killed him o “Acquired” Tycho’s data after his death o Figured out the (almost) true structure of the solar system - Kepler’s Breakthrough o Circular motions, while ideal, are not correct for describing planetary motions o Kepler found that elliptical orbits could fit the data without all the epicycles - Kepler’s Laws o From Brahe’s data, Kepler determined three empirical laws 1. The orbits of planets are ellipses with the Sun at one focus 2. The line joining a planet to the Sun sweeps out equal areas in equal times a. Near perihelion, in 30 days a planet sweeps out an area that is short but wide b. Near aphelion, in 30 days a planet sweeps out an area that is long but narrow c. The areas swept out in 30-day periods are all equal d. Note: speed changes with time, area does not i. Speed increases: accelerate ii. Speed decreases: decelerate 3. Planets with larger semi-major axes have longer periods with the following dependence: (P1/P2) 2 = (a1/a2) 3

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a. P= period. a = semi-major axis - Support for Kepler’s Model o Tycho’s data and Kepler’s Model showed that a heliocentric model
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This note was uploaded on 04/07/2009 for the course NATS 006 taught by Professor Eisner during the Spring '09 term at Arizona.

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NATS 2-3 - NATS February 3 Announcements Mid-term exam is...

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