Re: [Phys-L] dark matter

[Paul Nord <paul.nord@valpo.edu>]

Anthony,

A couple of problems with the cold matter explanation.
1. If it were dust, there would be enough to obscure starlight and it would
be heated and have an infrared signature.  We see this in planetary and
protoplanetary nebula.  Dust and gas clouds have been identified.  But
there isn't enough.
2. If it were compact objects like rogue planets, or black holes, there
would be enough of them that we would frequently see them blocking/focusing
starlight.
3. In observations of colliding galaxies, it appears that the matter and
the dark matter interact differently.  That is, the shape of the gas clouds
in the galaxies changes as they collide, but the dark matter continues its
motion; it doesn't interact - even with itself.

I'm no expert.  But I think the problem with dark matter is that the simple
explanations have been tried and they fall short.

Paul


On Wed, Aug 17, 2016 at 8:47 PM, Anthony Lapinski <alapinski@pds.org> wrote:

> The universe is confusing me, and I am no expert on dark matter and dark
> energy. I thought dark matter was "discovered" to explain the rotation of
> galaxies. So isn't it just matter that is not warm enough (like humans) to
> be seen with an optical telescope? But it still has gravitational effects
> like ordinary matter. I'm reading online that dark matter is a different
> kind of matter altogether, or is it just fundamental particles that can't
> be touched like ordinary matter? Does anybody really understand this?
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