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Thread: does newton cannonball contradict kepler?

  1. #1 does newton cannonball contradict kepler? 
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    kepler stated the sun is at the ellipse orbit focus

    check out how in the newton cannonball thought experiment as the ellipse grows the focus moves away from the planet:



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  3. #2  
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    What's your point? An ellipse has two foci. The earth would be one of them.


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  4. #3  
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    that for a bigger ellipse than a circunference the focus will move away from earth in newtons cannonball experiment which would make false kepler( as you can see in my drawing, you can see each ellipse numbered as its corresponding focus)

    i see a contradiction between kepler and newton

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  5. #4  
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    You ignored what I said about an ellipse having two foci. It is the second focus that moves, not the earth.
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    oh yes of course the second focus moves, but so does the first

    the way i see it you can see it too:

    look at my drawing and keep making bigger ellipses untill you make an ellipse the size of europe

    would you say as you look at that ellipse from space that the focus is at 2 cm distance distance from the border of the ellipse?

    that you have drawn an ellipse million of km big and its focus is at two cm of its extreme?

    it would have to be an ellipse of very extreme eccentricity which is not the case as you can approximatley see by drawing it
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  7. #6  
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    Quote Originally Posted by luxtpm
    oh yes of course the second focus moves, but so does the first

    the way i see it you can see it too:

    look at my drawing and keep making bigger ellipses untill you make an ellipse the size of europe
    Your drawing is crap. If the ellipse is the size of Europe, your cannonball would not be orbiting but would crash into the earth.
    would you say as you look at that ellipse from space that the focus is at 2 cm distance distance from the border of the ellipse?
    How in the world do you get a focus of 2 centimeters from the ellipse? It would have to be at least the radius of the earth if you launch it from the surface of the earth.
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  8. #7  
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    never mind

    i actually just realized i got this one wrong

    thanks
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