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Conference rusure::math

Title:Mathematics at DEC
Moderator:RUSURE::EDP
Created:Mon Feb 03 1986
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:2083
Total number of notes:14613

1110.0. "2-body problem solution?" by DWOVAX::YOUNG (in the iron grip of bureaucracy) Mon Aug 14 1989 01:10

    OK, I kno wthat there is no solution to the 3-body problem, however,
    can anybody tell me what the solution to the 2-body problem is?
    
    Better yet, can anyone give me a solution to the 2-body problem that
    takes relativity (special or General) into account?
    
    Thanks	Barry
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1110.1Problems...ARTMIS::MILLSHand 50g scepticism, at gas mark 4....Mon Aug 14 1989 08:2010
	Correct me if I'm wrong, but...

	The three body problem is unsolvable with Newtonian methods,
	The two body problem is unsolvable in relativity (Special or General)
	The one body problem is unsolvable in quantum physics (Heisenberg 
			uncertainty principle)
	Relativistic Quantum physics runs into problems with a vacuum :-)

				HRM
1110.2HPSTEK::XIAIn my beginning is my end.Mon Aug 14 1989 16:4024
    re .0 .1
    
    If you have only two bodies, then there are essentially three
    solutions for the Newtonian physics:
    
    1. Hyperbolic solution.  In this case the two bodies pass near each
       other and curve each other's orbits then go their separate ways.
    
    2. Elliptic solution.  Simply known as "earth orbiting the sun".
    
    3. Collision.
    
    If you want to go for other fancy theories, then here is what you have:
    
    General Relativity (Special Relativity does not make sense here since
    the theory does not work when you have gravity):  There are
    approximation methods for the two body problem.
    
    QM:  You can solve the problem exactly for two bodies (Hydrogen atom is
    an example).
    
    Eugene
                               
                                        
1110.3HPSTEK::XIAIn my beginning is my end.Mon Aug 14 1989 17:336
    Here is a little puzzle I just come up with.  Suppose you have two
    objects A and B (with mass M and m).  We know the initial positions and
    velocities of both objects, and we know the position of object A at all 
    time.  Derive a simple method to find object B at all time.
    
    Eugene 
1110.4BEING::POSTPISCHILAlways mount a scratch monkey.Mon Aug 14 1989 18:008
    Re .3:
    
    Given initial positions, velocities, and masses, the center of mass
    always travels in a known straight line.  B's position is linearly
    dependent upon A's position and the center of mass. 
    
    
    				-- edp
1110.5HPSTEK::XIAIn my beginning is my end.Mon Aug 14 1989 18:256
    re -1
    
    Ain't that a nice problem :-)?
    
    Eugene
    
1110.6ANT::JANZENcf. ANT::CIRCUITS,ANT::UWAVESMon Aug 14 1989 21:533
    The two body problem also has a parabolic solution newtonianly.
    like when you throw a rock
    Tom
1110.7DWOVAX::YOUNGin the iron grip of bureaucracyMon Aug 14 1989 23:476
    I was looking more for a closed solution.  I know that one exists
    because I had to derive it on a test in college.  Well, my math isn't
    as sharp today as it was then, so I was hoping that someone else could
    help me out.
    
    Should I post this in Physics instead?
1110.8AITG::DERAMODaniel V. {AITG,ZFC}:: D'EramoTue Aug 15 1989 03:318
        I vaguely recall that the math is a little tricky, but
        for the "Sun - Earth" solution (assume no relativistic
        effects, assume a large mass that is fixed with a smaller
        mass moving around it) you eventually get the "conic
        sections".  I play around with it a bit on paper and see
        if I can reconstruct it.
        
        Dan