<p>I think it is unlikely because of the importance of dark matter in more local dynamics.</p>
<p>Dark matter is necessary to be able to account for the dynamics of our galaxy, not just the behavior of distant galaxies that could potentially have this invisible matter. If it did exist, we would expect to see it in our own galaxy as well, and we don’t.</p>
<p>Furthermore (and I am emphasizing the rocks here because stars would be visible locally) Hydrogen and Helium make up 99% of the baryonic matter of the universe, so enough rocks to account for dark matter (which is 5x more abundant than baryonic matter) is unreasonable; we would definitely see them locally if they were there.</p>
<p>While I think what your mentioned most definitely contributes to effects that are attributed to dark matter in distant galaxies, I think for these reasons the effect would not be a leading order effect, and far from being able to be the entire solution.</p>

CC BY-SA 4.0
2022-12-20T21:27:13.520Z
2022-12-20T21:27:13.520Z
Justin T
<p>We tend to think of the universe as the visible universe, but there could be large amounts of eventually hierarchically ordered, normal, matter that we can only observe at relatively close distances.</p>
<p>An example is dwarf spheroid galaxies which are so faint that they can only be observed in the Local Group. Today, about fifty dwarf spheroid galaxies are known, and the first one was discovered just a hundred years ago. The stars in dwarf spheroid galaxies are almost all billions of years old and there are no gas clouds to cause new production.</p>
<p>Another example is rocks of the kind that build up planets. They originally come from other star systems and could exist in space both gravitationally bound to stars and galaxies and in more isotropic motions between stars and galaxies, both in aggregates and individually.</p>
<blockquote>
<p>My question is, is there any chance that the average density of such
(for us) invisible matter is close to the calculated density of dark
matter?</p>
</blockquote>

<dark-matter><dwarf-galaxy>
Could dark matter be ordinary cool matter far away?
Lehs
# Could dark matter be ordinary cool matter far away?

(Asked by: username_0 on 2022-12-20)

We tend to think of the universe as the visible universe, but there could be large amounts of eventually hierarchically ordered, normal, matter that we can only observe at relatively close distances.

An example is dwarf spheroid galaxies which are so faint that they can only be observed in the Local Group. Today, about fifty dwarf spheroid galaxies are known, and the first one was discovered just a hundred years ago. The stars in dwarf spheroid galaxies are almost all billions of years old and there are no gas clouds to cause new production.

Another example is rocks of the kind that build up planets. They originally come from other star systems and could exist in space both gravitationally bound to stars and galaxies and in more isotropic motions between stars and galaxies, both in aggregates and individually.

> My question is, is there any chance that the average density of such
> (for us) invisible matter is close to the calculated density of dark
> matter?

**Tags:** dark-matter, dwarf-galaxy


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## 1 answers

### Answer by username_1 on 2022-12-20. Score: 1

I think it is unlikely because of the importance of dark matter in more local dynamics.

Dark matter is necessary to be able to account for the dynamics of our galaxy, not just the behavior of distant galaxies that could potentially have this invisible matter. If it did exist, we would expect to see it in our own galaxy as well, and we don’t.

Furthermore (and I am emphasizing the rocks here because stars would be visible locally) Hydrogen and Helium make up 99% of the baryonic matter of the universe, so enough rocks to account for dark matter (which is 5x more abundant than baryonic matter) is unreasonable; we would definitely see them locally if they were there.

While I think what your mentioned most definitely contributes to effects that are attributed to dark matter in distant galaxies, I think for these reasons the effect would not be a leading order effect, and far from being able to be the entire solution.


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