<p>Given what we know of entropy and of the expansion of the Universe, the answer to your question is of course "Yes".</p>

<p>It will take a really really long time, however. </p>

<p>Edited to add:</p>

<p>"...a really really long time..." is an intentionally vague description.  Whether it is 10<sup>10</sup> or 10<sup>10<sup>10</sup></sup> Hubble times is open to question.  </p>

CC BY-SA 3.0
2014-01-13T18:04:24.937Z
Could you be a little bit more precise and indicate, what do you really mean by really really long? Is it several Hubble times, or $10^{10}$ Hubble times, or $10^{10^{10}}$?
Alexey Bobrick
CC BY-SA 3.0
2014-01-13T21:54:28.133Z
How precise do you need it, @AlexeyBobrick?
Cyberherbalist
CC BY-SA 3.0
2014-01-13T22:31:46.240Z
As precise as possible :)
Alexey Bobrick
CC BY-SA 3.0
2014-01-13T22:44:12.343Z
OK, @AlexeyBobrick, how about 983.98332 x 10^10  Hubble times?
Cyberherbalist
CC BY-SA 3.0
2014-01-13T22:45:57.823Z
Nice, but not very convincing, sorry.
Alexey Bobrick
CC BY-SA 3.0
2014-01-13T22:47:20.237Z
Not very convincing?  I am devastated.  :)
Cyberherbalist
CC BY-SA 3.0
2014-01-13T23:27:19.360Z
Well, to share something positive, here is an artists impression of a multiverse: http://www.physicsoftheuniverse.com/images/bigbang_multiverse.jpg , enjoy!
Alexey Bobrick
CC BY-SA 3.0
2014-01-13T17:04:32.943Z
2014-01-13T22:20:30.003Z
2014-01-13T22:20:30.003Z
Cyberherbalist
<p><a href="http://phys.org/news/2012-11-cosmic-gdp-star-formation-slumps.html" rel="noreferrer">Cosmic GDP has already crashed</a>, as Peak Star was ~11 billion years ago.
<img src="https://i.sstatic.net/rDhA4.jpg" alt="Cosmic GDP"></p>

<p>According to <a href="http://arxiv.org/abs/1202.3436" rel="noreferrer">Sobral et al</a>'s prediction, the future star production by mass will give only 5% of the stars in the universe today, "even if we wait forever." More theoretical predictions, such as <a href="http://arxiv.org/abs/astro-ph/9701131" rel="noreferrer">this one</a>, suggest that nebulae will run out of hydrogen on the order of $10^{13}$ years, while star formation will occasionally happen due to collision of brown dwarfs until somewhere on the order of $10^{14}$ years.</p>

<p>Of course, hydrogen itself may have a finite lifetime. The half-life of a proton is experimentally known to be longer than $10^{34}$ years, but it may still be quite finite.</p>

CC BY-SA 3.0
2014-01-13T20:30:36.463Z
I thought I remembered reading something about this, but I couldn't remember where so I left it to someone else to answer. +1
called2voyage
CC BY-SA 3.0
2014-01-13T22:02:11.803Z
Very well explained. Exactly the answer I was looking for. Thank you!
Ranveer
CC BY-SA 3.0
2014-01-13T23:39:04.467Z
@called2voyage Brian Cox did a nice show on this in his "Wonders of the Universe" series, but if I recall, he got a bit poetic in specifying the time frames involved. Basically a really really really long time.
Robert Cartaino
CC BY-SA 3.0
2014-01-14T11:13:31.290Z
Could it be that at after a certain time, the "dark matter" observed, will become hydrogen? Perhaps after such a long time, that we could never observe it close enough?
frodeborli
CC BY-SA 3.0
2014-01-14T11:18:24.183Z
@frodeborli: If it were the case, that would shift the "no more new stars" date upwards. But there's no reason to believe it.
Stan Liou
CC BY-SA 3.0
2014-01-14T11:41:22.597Z
@StanLiou I agree that there's no reason to believe it. It's just an idea. I think ideas are important, and sometimes worth to explore.
frodeborli
CC BY-SA 3.0
2014-01-14T13:08:45.927Z
@frodeborli, a very interesting idea, by the way. Indeed, how do we know if DM particles are stable.
Alexey Bobrick
CC BY-SA 3.0
2014-01-14T13:26:55.173Z
@AlexeyBobrick Thank you; it would seem to make the universe a continuous flow instead of something with a beginning and an end, which is a somewhat pleasing thought. How can I find out if somebody else have explored the idea before?
frodeborli
CC BY-SA 3.0
2014-01-14T13:36:59.557Z
@frodeborli: As dark matter particle hasn't been identified, I don't think anybody considered its lifetimes, except for that they are obviously longer than Hubble time. But you can surely ask a question here on on Physics SE. By the way, http://arxiv.org/abs/1307.6434 .
Alexey Bobrick
CC BY-SA 3.0
2014-01-14T13:42:25.550Z
@AlexeyBobrick I did at http://astronomy.stackexchange.com/questions/1435/could-dark-matter-be-unstable.
frodeborli
CC BY-SA 3.0
2014-01-13T20:21:19.280Z
2014-01-13T20:21:19.280Z
Stan Liou
<p>New stars keep forming in the universe thanks to all the nebulae. Now, we need Hydrogen to form stars and there would a time when all the hydrogen will get exhausted, and no more star formation will take place, theoretically.</p>

<p>Will there practically be such a point of time? I guess there is no place where hydrogen is replenished after star formation. Or is there a feedback cycle?</p>

CC BY-SA 3.0
2014-01-13T16:38:24.047Z
There is no feedback cycle, there will be a point where no stars form anymore, [entropy](http://en.wikipedia.org/wiki/Entropy#Cosmology) dictates it.
Eduardo Serra
CC BY-SA 3.0
2014-01-13T16:53:56.283Z
@EduardoSerra To be more precise, there is a feedback cycle, but it is a negative feedback rather than a positive. Entropy is the law of decreasing returns essentially.
called2voyage
CC BY-SA 3.0
2014-01-14T13:11:15.687Z
Who deleted my comment? There is a positive feedback cycle, which is very weak though. Protons and antiprotons can be produced in black hole evaporation as a side product.
Alexey Bobrick
<star><nebula><star-formation>
Will new stars stop forming at some point of time?
Ranveer
# Will new stars stop forming at some point of time?

(Asked by: username_0 on 2014-01-13)

New stars keep forming in the universe thanks to all the nebulae. Now, we need Hydrogen to form stars and there would a time when all the hydrogen will get exhausted, and no more star formation will take place, theoretically.

Will there practically be such a point of time? I guess there is no place where hydrogen is replenished after star formation. Or is there a feedback cycle?

**Tags:** star, nebula, star-formation

> **Comments:**
> **username_1**: There is no feedback cycle, there will be a point where no stars form anymore, [entropy](http://en.wikipedia.org/wiki/Entropy#Cosmology) dictates it.  
> **username_2**: @username_1 To be more precise, there is a feedback cycle, but it is a negative feedback rather than a positive. Entropy is the law of decreasing returns essentially.  
> **username_3**: Who deleted my comment? There is a positive feedback cycle, which is very weak though. Protons and antiprotons can be produced in black hole evaporation as a side product.  

---

## 2 answers

### Answer by username_5 on 2014-01-13. Score: 15 | Accepted answer

[Cosmic GDP has already crashed](http://phys.org/news/2012-11-cosmic-gdp-star-formation-slumps.html), as Peak Star was ~11 billion years ago.
![Cosmic GDP](https://i.sstatic.net/rDhA4.jpg)

According to [Sobral et al](http://arxiv.org/abs/1202.3436)'s prediction, the future star production by mass will give only 5% of the stars in the universe today, "even if we wait forever." More theoretical predictions, such as [this one](http://arxiv.org/abs/astro-ph/9701131), suggest that nebulae will run out of hydrogen on the order of $10^{13}$ years, while star formation will occasionally happen due to collision of brown dwarfs until somewhere on the order of $10^{14}$ years.

Of course, hydrogen itself may have a finite lifetime. The half-life of a proton is experimentally known to be longer than $10^{34}$ years, but it may still be quite finite.

> **Comments:**
> **username_2**: I thought I remembered reading something about this, but I couldn't remember where so I left it to someone else to answer. +1  
> **username_0**: Very well explained. Exactly the answer I was looking for. Thank you!  
> **username_6**: @username_2 Brian Cox did a nice show on this in his "Wonders of the Universe" series, but if I recall, he got a bit poetic in specifying the time frames involved. Basically a really really really long time.  
> **username_7**: Could it be that at after a certain time, the "dark matter" observed, will become hydrogen? Perhaps after such a long time, that we could never observe it close enough?  
> **username_5**: @username_7: If it were the case, that would shift the "no more new stars" date upwards. But there's no reason to believe it.  
> **username_7**: @username_5 I agree that there's no reason to believe it. It's just an idea. I think ideas are important, and sometimes worth to explore.  
> **username_3**: @username_7, a very interesting idea, by the way. Indeed, how do we know if DM particles are stable.  
> **username_7**: @username_3 Thank you; it would seem to make the universe a continuous flow instead of something with a beginning and an end, which is a somewhat pleasing thought. How can I find out if somebody else have explored the idea before?  
> **username_3**: @username_7: As dark matter particle hasn't been identified, I don't think anybody considered its lifetimes, except for that they are obviously longer than Hubble time. But you can surely ask a question here on on Physics SE. By the way, http://arxiv.org/abs/1307.6434 .  
> **username_7**: @username_3 I did at http://astronomy.stackexchange.com/questions/1435/could-dark-matter-be-unstable.  

---

### Answer by username_4 on 2014-01-13. Score: 2

Given what we know of entropy and of the expansion of the Universe, the answer to your question is of course "Yes".

It will take a really really long time, however.

Edited to add:

"...a really really long time..." is an intentionally vague description. Whether it is 1010 or 101010 Hubble times is open to question.

> **Comments:**
> **username_3**: Could you be a little bit more precise and indicate, what do you really mean by really really long? Is it several Hubble times, or $10^{10}$ Hubble times, or $10^{10^{10}}$?  
> **username_4**: How precise do you need it, @username_3?  
> **username_3**: As precise as possible :)  
> **username_4**: OK, @username_3, how about 983.98332 x 10^10  Hubble times?  
> **username_3**: Nice, but not very convincing, sorry.  
> **username_4**: Not very convincing?  I am devastated.  :)  
> **username_3**: Well, to share something positive, here is an artists impression of a multiverse: http://www.physicsoftheuniverse.com/images/bigbang_multiverse.jpg , enjoy!  

---

