<p>Your friend sounds confused. Maybe this answer helps to address your friend's confusion in a charitable way. TLDR: Yes, it is hard to form stars, but the Universe is large, so even if only 1% of gas can form stars, you still get a lot of stars.</p>
<p>We know stars form. We see them. However, there are many things we do not fully understand about star formation. Star formation is ultimately a complex dance between gravity, which brings gas and dust together, and pressure/turbulence/magnetic fields, which tends to keep gas and dust from collapsing.</p>
<p>It turns out that star formation is very inefficient. And it can be simultaneously true that we have evidence that:</p>
<ul>
<li>Star formation is inefficient</li>
<li>Pressure, turbulence, and magnetic fields play a role preventing star formation</li>
<li>Stars exist nonetheless, because even if only 1% of gas is forming stars, there are still stars.</li>
</ul>
<p>None of this is evidence that star formation is impossible. Only that it is &quot;rare&quot; from the POV that only a small fraction of gas is in stars at any given time. If your friend is willing to accept all these truths simultaneously, then you can have an interesting discussion, because &quot;why star formation is inefficient&quot; is indeed very interesting, and trying to understand the role of pressure/magnetic fields/turbulence is also very interesting! And perhaps lets you better appreciate each star that managed to &quot;make it.&quot;</p>
<p>There are too many sources to count (star formation is an entire active subfield of Astrophysics) so I recommend searching for the following:</p>
<ul>
<li>Star formation efficiency (how much of the gas is in stars? This depends on object: galaxy, giant molecular cloud, etc.). You'll find numbers close to 1-5%.</li>
<li>Star formation efficiency per free-fall time (how fast do stars form compared to how fast they could be forming, assuming the gas is in free-fall gravitational collapse). For galaxies, this is very small, but gets more efficient as you get closer to objects that really are gravitationally collapsing.</li>
<li>Jeans instability</li>
<li>Role of magnetic fields in star formation</li>
<li>Role of turbulence in star formation</li>
</ul>

CC BY-SA 4.0
2024-08-12T09:12:35.010Z
Thank you Alwin for actually being positive and helpful. It is somewhat rare online, people mostly just want to be unhelpful. Like pointing out that "um actually the other guy should have to prove his claim" *rolls eyes* You rock and thank you, wish I had rep to give bounty for it.
Wyrsa
CC BY-SA 4.0
2024-08-09T22:28:08.083Z
2024-08-09T22:28:08.083Z
Alwin
<blockquote>
<p>I'm dealing with someone who claims there is &quot;loads of evidence&quot;</p>
</blockquote>
<p>Science is based on the principle that if you make a wild claim <em>you</em> have to support it with evidence.  Making vague assertions that other people say this makes it virtually impossible to refute the argument.</p>
<p>Your friend has to provide concrete evidence, not anyone else.</p>
<blockquote>
<p>that star formation is impossible due to the above issue. Apparently gas would repel itself and not form a concentrated mass.</p>
</blockquote>
<p>Which is a weird claim to make for someone who is a bag of atoms and molecules, held together by electromagnetic forces and living on a ball of material held together by gravity, who is also entirely dependent on the Sun to stop freezing (and starving - sunlight powers plant growth), a huge ball of stuff held together by gravity.</p>
<p>Your friend could not exist if what they said was true.</p>

CC BY-SA 4.0
2024-08-09T08:41:37.397Z
2024-08-09T08:41:37.397Z
StephenG - Help Ukraine
<p>My question is based on a separate conversation I've been having. And forgive my very simple phrasing of the question I have below.</p>
<blockquote>
<p>Is there any evidence that gravity would lose the &quot;battle&quot; against gas/dust due to them repelling each other? Specifically in respect to our understanding of star formation.</p>
</blockquote>
<p>I'm dealing with someone who claims there is &quot;loads of evidence&quot; that star formation is impossible due to the above issue. Apparently gas would repel itself and not form a concentrated mass.</p>
<p>So... does anyone know of any evidence that might support this claim or can someone clarify exactly how silly the argument this guy made was?
Thanks in advance.</p>

CC BY-SA 4.0
2024-08-08T11:59:31.713Z
So you are asking us for what evidence there is that stars don't form?? It is unclear what the issue is. Gas and dust don't repel each other.
ProfRob
CC BY-SA 4.0
2024-08-08T12:30:31.937Z
I agree the premise is silly! Can anyone just stomp this nonsense into the dirt so to speak? I think the person I was talking to is assuming magnetic forces are stronger than gravity so ions should repel each other... idk, I just want someone to stomp the argument with science :)
Wyrsa
CC BY-SA 4.0
2024-08-08T12:54:32.537Z
By "repelling", does the person perhaps refer to the _pressure_ of a gas increasing as a cloud is compressed? If so, yes indeed star formation is impossible unless the cloud is very massive (so it can overcome pressure), or efficient at cooling (so it can relieve the pressure). This is the essence of the [Jeans collapse criterion](https://en.wikipedia.org/wiki/Jeans_instability). So if thousands of stars on the sky is not evidence enough, you can point them to this article.
pela
CC BY-SA 4.0
2024-08-08T20:14:15.953Z
I suspect that the guy you're arguing with is attempting to promote the notorious crackpot "plasma theory", aka the Electric Universe theory. See https://astronomy.stackexchange.com/a/21527/16685 & https://physics.stackexchange.com/q/18950/123208
PM 2Ring
CC BY-SA 4.0
2024-08-09T01:52:40.540Z
@Wyrsa if you found your answer, please feel free to self answer it. Self answer is appreciated and it also helps future readers.
Nilay Ghosh
CC BY-SA 4.0
2024-08-09T03:53:36.947Z
I’m voting to close this question because questions of the form "my friend has a crazy theory, what's the best answer to it?" are off-topic.
Chappo Hasn't Forgotten
CC BY-SA 4.0
2024-08-12T09:15:13.877Z
@PM2Ring Actually it is so much worse, he claims that Neil deGrasse Tyson said "if we didn't know stars existed, we wouldn't believe they could form at all" and then misquotes him from that book he wrote... and then tries to prove that most of astrophysics is inaccurate and we can't trust science it is all flawed... and on and on.
Wyrsa
CC BY-SA 4.0
2024-08-12T10:47:07.067Z
Really, it's a waste of energy arguing with such people. They're not responsive to valid input,  they just want to convince you that you're wrong. But if you wish to persist, you may find RationalWiki helpful, eg https://rationalwiki.org/wiki/Argument_from_ignorance & https://rationalwiki.org/wiki/Willful_ignorance
PM 2Ring
CC BY-SA 4.0
2024-08-12T11:20:50.300Z
Oh trust me I know, but I mean you don't get to pick who is near you and what they are... :)
Wyrsa
<star-formation>
Fundamental question about Star formation with respect to gas density and gravity
Wyrsa
# Fundamental question about Star formation with respect to gas density and gravity

(Asked by: username_0 on 2024-08-08)

My question is based on a separate conversation I've been having. And forgive my very simple phrasing of the question I have below.

> Is there any evidence that gravity would lose the "battle" against gas/dust due to them repelling each other? Specifically in respect to our understanding of star formation.

I'm dealing with someone who claims there is "loads of evidence" that star formation is impossible due to the above issue. Apparently gas would repel itself and not form a concentrated mass.

So... does anyone know of any evidence that might support this claim or can someone clarify exactly how silly the argument this guy made was?
Thanks in advance.

**Tags:** star-formation

> **Comments:**
> **username_1**: So you are asking us for what evidence there is that stars don't form?? It is unclear what the issue is. Gas and dust don't repel each other.  
> **username_0**: I agree the premise is silly! Can anyone just stomp this nonsense into the dirt so to speak? I think the person I was talking to is assuming magnetic forces are stronger than gravity so ions should repel each other... idk, I just want someone to stomp the argument with science :)  
> **username_2**: By "repelling", does the person perhaps refer to the _pressure_ of a gas increasing as a cloud is compressed? If so, yes indeed star formation is impossible unless the cloud is very massive (so it can overcome pressure), or efficient at cooling (so it can relieve the pressure). This is the essence of the [Jeans collapse criterion](https://en.wikipedia.org/wiki/Jeans_instability). So if thousands of stars on the sky is not evidence enough, you can point them to this article.  
> **username_3**: I suspect that the guy you're arguing with is attempting to promote the notorious crackpot "plasma theory", aka the Electric Universe theory. See https://astronomy.stackexchange.com/a/21527/16685 & https://physics.stackexchange.com/q/18950/123208  
> **username_4**: @username_0 if you found your answer, please feel free to self answer it. Self answer is appreciated and it also helps future readers.  
> **username_5**: I’m voting to close this question because questions of the form "my friend has a crazy theory, what's the best answer to it?" are off-topic.  
> **username_0**: @PM2Ring Actually it is so much worse, he claims that Neil deGrasse Tyson said "if we didn't know stars existed, we wouldn't believe they could form at all" and then misquotes him from that book he wrote... and then tries to prove that most of astrophysics is inaccurate and we can't trust science it is all flawed... and on and on.  
> **username_3**: Really, it's a waste of energy arguing with such people. They're not responsive to valid input,  they just want to convince you that you're wrong. But if you wish to persist, you may find RationalWiki helpful, eg https://rationalwiki.org/wiki/Argument_from_ignorance & https://rationalwiki.org/wiki/Willful_ignorance  
> **username_0**: Oh trust me I know, but I mean you don't get to pick who is near you and what they are... :)  

---

## 2 answers

### Answer by username_6 on 2024-08-09. Score: 3 | Accepted answer

Your friend sounds confused. Maybe this answer helps to address your friend's confusion in a charitable way. TLDR: Yes, it is hard to form stars, but the Universe is large, so even if only 1% of gas can form stars, you still get a lot of stars.

We know stars form. We see them. However, there are many things we do not fully understand about star formation. Star formation is ultimately a complex dance between gravity, which brings gas and dust together, and pressure/turbulence/magnetic fields, which tends to keep gas and dust from collapsing.

It turns out that star formation is very inefficient. And it can be simultaneously true that we have evidence that:

* Star formation is inefficient
* Pressure, turbulence, and magnetic fields play a role preventing star formation
* Stars exist nonetheless, because even if only 1% of gas is forming stars, there are still stars.

None of this is evidence that star formation is impossible. Only that it is "rare" from the POV that only a small fraction of gas is in stars at any given time. If your friend is willing to accept all these truths simultaneously, then you can have an interesting discussion, because "why star formation is inefficient" is indeed very interesting, and trying to understand the role of pressure/magnetic fields/turbulence is also very interesting! And perhaps lets you better appreciate each star that managed to "make it."

There are too many sources to count (star formation is an entire active subfield of Astrophysics) so I recommend searching for the following:

* Star formation efficiency (how much of the gas is in stars? This depends on object: galaxy, giant molecular cloud, etc.). You'll find numbers close to 1-5%.
* Star formation efficiency per free-fall time (how fast do stars form compared to how fast they could be forming, assuming the gas is in free-fall gravitational collapse). For galaxies, this is very small, but gets more efficient as you get closer to objects that really are gravitationally collapsing.
* Jeans instability
* Role of magnetic fields in star formation
* Role of turbulence in star formation

> **Comments:**
> **username_0**: Thank you username_6 for actually being positive and helpful. It is somewhat rare online, people mostly just want to be unhelpful. Like pointing out that "um actually the other guy should have to prove his claim" *rolls eyes* You rock and thank you, wish I had rep to give bounty for it.  

---

### Answer by username_7 on 2024-08-09. Score: 1

> I'm dealing with someone who claims there is "loads of evidence"

Science is based on the principle that if you make a wild claim *you* have to support it with evidence. Making vague assertions that other people say this makes it virtually impossible to refute the argument.

Your friend has to provide concrete evidence, not anyone else.

> that star formation is impossible due to the above issue. Apparently gas would repel itself and not form a concentrated mass.

Which is a weird claim to make for someone who is a bag of atoms and molecules, held together by electromagnetic forces and living on a ball of material held together by gravity, who is also entirely dependent on the Sun to stop freezing (and starving - sunlight powers plant growth), a huge ball of stuff held together by gravity.

Your friend could not exist if what they said was true.


---

