<p>Hydrogen clouds don't even make up a small component of dark matter, because hydrogen is not dark. The image below depicts the emission spectrum of hydrogen in the visible regime (a.k.a., the <a href="http://en.wikipedia.org/wiki/Balmer_series" rel="nofollow noreferrer">Balmer series</a>).</p>

<p><img src="https://i.sstatic.net/79N24.jpg" alt="enter image description here"></p>

<p>The emission spectrum of dark matter on the other hand would be completely black.</p>

<p>Dark matter is gets its name from the fact that it doesn't absorb or emit light, i.e., electromagnetic radiation. From an elementary particle standpoint, this means dark matter particles can't interact with photons via the electromagnetic force at all, so dark matter particles must be electrically neutral, which electrons and protons certainly are not. No electrons are protons means no hydrogen atoms.</p>

CC BY-SA 3.0
2014-04-05T22:28:13.863Z
I agree that matter between universes would not emit light since there is not enough energy. But the density may be low enough so that you cannot tell that it is absorbing light. Can you tell exactly how thick glass is by shining visible light through it? My guess is that you could be off by 10%.
LDC3
CC BY-SA 3.0
2014-04-05T22:21:05.573Z
2014-04-05T22:21:05.573Z
David H
<p>From watching a video on youtube, it states that Dark Matter is 6 times more abundant than known matter. I was wondering if it was possible to have hydrogen clouds between the <strike>universes</strike> galaxies. The density would need to be less than inside <strike>universes</strike> galaxies (since star formation would be possible). </p>

<p>Is it possible that hydrogen clouds be a major component of Dark Matter?</p>

CC BY-SA 3.0
2014-04-06T03:56:47.123Z
I'm not sure what you mean by universes. Are you speaking of a multi verse system or are you speaking of galaxies? Because you seem to be speaking of galaxies.
Re Captcha
CC BY-SA 3.0
2014-04-06T04:00:48.337Z
You're right, I should have said galaxies.
LDC3
<dark-matter><hydrogen>
Density of hydrogen between galaxies
LDC3
# Density of hydrogen between galaxies

(Asked by: username_0 on 2014-04-05)

From watching a video on youtube, it states that Dark Matter is 6 times more abundant than known matter. I was wondering if it was possible to have hydrogen clouds between the universes galaxies. The density would need to be less than inside universes galaxies (since star formation would be possible).

Is it possible that hydrogen clouds be a major component of Dark Matter?

**Tags:** dark-matter, hydrogen
> **Comments:**
> **username_1**: I'm not sure what you mean by universes. Are you speaking of a multi verse system or are you speaking of galaxies? Because you seem to be speaking of galaxies.  
> **username_0**: You're right, I should have said galaxies.  

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## 1 answers

### Answer by username_2 on 2014-04-05. Score: 2

Hydrogen clouds don't even make up a small component of dark matter, because hydrogen is not dark. The image below depicts the emission spectrum of hydrogen in the visible regime (a.k.a., the [Balmer series](http://en.wikipedia.org/wiki/Balmer_series)).

![enter image description here](https://i.sstatic.net/79N24.jpg)

The emission spectrum of dark matter on the other hand would be completely black.

Dark matter is gets its name from the fact that it doesn't absorb or emit light, i.e., electromagnetic radiation. From an elementary particle standpoint, this means dark matter particles can't interact with photons via the electromagnetic force at all, so dark matter particles must be electrically neutral, which electrons and protons certainly are not. No electrons are protons means no hydrogen atoms.

> **Comments:**
> **username_0**: I agree that matter between universes would not emit light since there is not enough energy. But the density may be low enough so that you cannot tell that it is absorbing light. Can you tell exactly how thick glass is by shining visible light through it? My guess is that you could be off by 10%.  

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