Quote:
Originally Posted by mugaliens
Actually, it's because only those stars within any given star's orbit contributes to it's orbital velocity. Thus, the innermost star is only affected by our galaxy's supermassive black hole, wile the outermost star is being affected by all other stars in our galaxy.
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I wish that were true. It would simplify things tremendously. Unfortunately, it's not true for the gravitation of a disk, but applies to points within a sphere only, where the mass outside of the orbit cancels itself out naturally due to the geometry. I think it is interesting that a point that is located anywhere within the central cavity of a hollowed out sphere will experience no gravity whatsoever, anywhere from the center of the sphere to the boundary of the cavity. However, the stars outside of a given star's orbit in a disk will also make a difference with the force and orbital speed. That's part of what makes it so complicated.
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The Grand Puzzle . (website)
"Let's define another operator, Sz, which we won't pay any attention to."
"This transformation will automatically make zero equal zero."
"It may be true that zero equals zero -- and that is certainly an equality -- but I don't want to go into the details at this time."