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B Kepler's Laws of planetary motion

  1. Jun 5, 2016 #1
    Whose observations did Kepler use to prove that planets do in fact orbit in ellipses ?? Was it Tycho's observations?
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  3. Jun 5, 2016 #2


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  4. Jun 6, 2016 #3


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    You really have to hand it to those early astronomers. Everything was measured using the naked eye and some very crude instruments. No Go-To telescopes available in those days. I guess the only thing on their side would have been No Light Pollution. (Put that candle out!!)
  5. Jun 6, 2016 #4


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    I don't think I would use the word "crude" to describe Tycho's Great Equatorial Armillary that he used to gather the observations that Kepler used. See the attached drawing. It was 3 meters in diameter and accurate to approximately 1 minute of arc. Of course we can do much better today, but for the time it was a very well designed and impressive instrument.

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  6. Jun 6, 2016 #5


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    The word "crude" was comparative and not intended to offend anyone. I wouldn't mind betting that Keppler himself would have used the word if he could see what we use now.
    One minute of arc is, in some respects, a barn door. The accuracy of clocks (time is as important as angle) was not good and I would reckon that accuracy of measuring long baselines would also not be very special.
    No.They did a great job with what they had to hand.
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