On Thu, Jan 13, 2011 at 9:19 PM, <mix...@bigpond.com> wrote: > In reply to Mauro Lacy's message of Thu, 13 Jan 2011 09:23:01 -0300: > Hi, > [snip] > >Let's calculate the acceleration produced by 200 million suns. This is > >doomed to fail because, as we know, galaxies don't obey Newton's > >gravitational law, but just to have an idea: > >a= Fg/msun = G msun*2*10^11/(26000 * 9.4607305e+15)^2 = > >4.3882998825*10^-10 m/s^2 > > > >Which is two times the centripetal acceleration... if we suppose that > >the central bulge contains half the visible mass, the standard > >calculation will coincide with the observed values for our Sun. But it > >will fail for stars farther from the center, which are also moving at > >250 km/s. > > > >In the wikipedia entry > >https://secure.wikimedia.org/wikipedia/en/wiki/Milky_Way > >you can see the expected vs. observed galactic rotation curves > > > https://secure.wikimedia.org/wikipedia/en/wiki/File:Rotation_curve_%28Milky_Way%29.JPG > > > >And they inf fact coincide in the case of our Sun. > > > >Anyways, any effect smaller than, let's say, 2*10^-11 m/s^2, can be > >safely ignored. > [snip] > I would be interested in a calculation of the strength of the magnetic > attraction/repulsion between the galactic magnetic field and the Solar > magnetic > field, and by how many orders of magnitude it differs. >
Sounds relevant, but I have nothing to add. David
