Re: Horizon on Dark Matter

Thus spake Oz <Oz@xxxxxxxxxxxxxxxxxxxx>
Charles Francis <charles@xxxxxxxxxxxxxxxx> writes

You may be right, but I don't see how it could be analysed. The dark
matter halo is generally described a sort of globule around the center
of the galaxy, but the actual distribution of matter in each halo is
different for each galaxy, always being just right to give the MOND law
whatever the distribution of visible matter.

Its more complex than this. You can work out the distribution for a
constant orbital velocity. I did this once and iirc its lots mass right
out to the star you are measuring and by implication beyons.

Yes. It must be. And now that the are finding all these ultraviolet
stars, the galaxy may be two or three times the radius it appears.

Somewhere half way between
the galaxies there is a zero field, but we can't measure accelerations
there as we don't have an orbiting eigenstate. The motion of the cloud
between the galaxies will depend on initial conditions, which we do not
know.

Well, we more-or-less know on average in a galactic cluster at least.
Or, more to the point, measure between two galaxies RIGHT ACROSS FROM
ONE TO THE OTHER. If the rotation speed appears to be the same
throughout (and I think it will) then dark matter is buggered.

Rotation speed is constant is an approximate law at best. For Low
Surface Brightness galaxies (sparsely populated with stars) rotation
speed actually keeps rising over the observed radius. The galaxies
themselves probably don't both lie in the same plane. Add the
theoretical difficulties to the experimental ones, and it doesn't look
like an easy or promising problem to tackle.


Regards

--
Charles Francis
Please reply by name
.

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