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How could one explain the collision of two continuous mass distributions in view of

gravitation (Newtonanian and General relativity) ?

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closed as not a real question by mbq, Ebenezer Sklivvze, Cedric H., Marek, Tobias Kienzler Nov 22 '10 at 8:20

It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.If this question can be reworded to fit the rules in the help center, please edit the question.

    
What exactly is it that you want explained about the collision? –  David Z Nov 19 '10 at 5:35
    
@David Zaslavsky: I have asked in a cooment on Jerry Schrimer's answer. –  Rajesh D Nov 19 '10 at 6:08
    
I think you are all going too far with this black hole thing, my opinion is that he is just asking the different between the scattering of point-like particles and the scattering of spheres; this can be treated due to gravitational or electrostatic interactions (if the spheres are charged). No big deal with GR. Unless the question is very very strange ... –  Cedric H. Nov 20 '10 at 19:40
    
@Cedric H.: What do you think a black hole is ? a discontinuity in a mass distribution ? –  Rajesh D Nov 20 '10 at 19:52
    
@Rajesh: At first your question was not clear at all... I interpreted by "point mass" a geometrical point affected with a mass. A classical scattering problem like the one of a charged point-like particle. –  Cedric H. Nov 21 '10 at 10:58

2 Answers 2

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In the context of classical mechanics, your question is probably ill-formed.

Since point masses have no physical extent, the gravitational force increases without bound as r approached zero, which it will indeed do because they'll only collide when they're superposed.

Infinite force on a finite mass implies infinite acceleration (F = ma) which implies infinite velocity, which is inconsistent with special relativity.

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In General Relativity, a point mass is a black hole. The collision of two black holes is a very complicated problem that has to be solved using numeric supercomputer simulation. The short story is that they end up coalescing to a single black hole.

There are some complications from this answer that could arise from spin-orbit coupling, but I don't think that's what you're asking about.

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Ok....i did'nt know that point masses are black holes. I was thinking that any system of particles as a system composed of point masses. Looks like in mechanics it seem to be a continuous distribution of mass. My question is what happens when two sperical distributions of mass collide ? Will they ? Even befor that how would a spherical(any shape) distribution of mass exist in view of gravity ? –  Rajesh D Nov 19 '10 at 6:07
    
depending on your answer i would want to ask more questions. –  Rajesh D Nov 19 '10 at 6:17

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