Hi Steven, thank you for your clarification.
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Originally Posted by sjastro
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If the small mass has the value Ep=0 when the large mass contracts and remains at the same point in the deeper well, Ep is no longer zero.
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OK so far.
Quote:
Originally Posted by sjastro
This means the small mass is performing work, that is KE is being converted into PE. The small mass loses KE equalling the difference in the depths of the well before and after contraction.
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Now we came to the sticky point (for me and for some others, I am sure). Even if the distance of masses centres remain the same?
So what is happening to the proposed circular orbit?
Or, does the shape of the well change, apart from just being extended downwards? The curve was supposed to indicate the energy as a function of the distance from the centre. If this is so then I've got it.. if not.. well then I have a problem
Because I always believed in a principle that the extended mass (star) can be replaced with point like mass of equal value, without small mass (planet) ever noticing the difference, for the purpose of orbit calculations (and that involves potential and kinetic energies of course - all according to classical mechanic)