[LibWhacker]

But remember, Vera Rubin showed the outer rim of a galaxy rotates just as fast as the stars interior to it. Everything's rotating like a giant phonograph record. See my comment #8 above. The only explanation is dark matter, or so they say. I believe they.

[Moonman62]

Actually, the flatness that Rubin discovered only applies to the outer bands. The inner and middle bands vary quite a bit in velocity. Some outer bands are nearly flat and some trend up as pictured above. Essentially, she discovered one of the important effects of dark matter.