> For years people have tried to modify the law of gravitation so that it is
> consistent with what we see with our telescopes but it just doesn't work. If
> you observe the Bullet Cluster what you see is 2 clusters colliding and the
> regular matter that we can see staying in the center just as we'd expect
> regular matter to do and the Dark Matter (detected by gravitational lensing)
> remained spread out just as you'd expect Dark Matter to do. There is no way
> modifying gravity can explain that.
> And in addition, if you tinker with gravity so that galaxies like our own
> Milky Way hold together and behave as they should then galactic clusters
> like the Local group don't behave as we see them do. And if you tinker with
> gravity in another way so that galactic clusters behave as they do in our
> telescopes then individual galaxies don't. But if you invoke Dark Matter
> then everything comes out fine.
>   John K Clark

On Fri, Nov 29, 2013 at 10:26 PM, meekerdb <meeke...@verizon.net> wrote:

> First, that isn't just assumed.  Other theories to explain it have been put
> forward, e.g. modifications of GR.  But so far they have all been
> invalidated by observations, whereas the hypothesis that it is some kind of
> matter that interacts only (or almost only) via gravity has survived an
> increasing variety of observations.
>> As far
>> as I understand, QM hasn't been reconciled with GR gravity. Isn't this
>> + dark matter a sign that there's something fundamental we don't
>> understand yet?
> There's certainly somethings we don't understand yet.  Whether dark matter
> is 'fundamental', in the sense that QM and GR are fundamentally in conflict,
> is possible but not supported by any data yet.
> Brent

John and Brent,

Thanks for the explanations. Ok, I think I now understand why dark
matter is the best hypothesis.


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