<p>As others have mentioned in the comments, there wouldn't have been any oxygen to form water. Soon after the Big Bang, the protons were hot or dense enough to fuse up to helium and some lithium but nothing heavier. Heavier elements were eventually fused in the first stars and partially dispersed in space by their winds and when they exploded as supernovae, but the first stars probably didn't form for a few hundred million years after the Big Bang.</p>
<p>For more information, have a look at the Wikipedia articles on <a href="https://en.wikipedia.org/wiki/Big_Bang_nucleosynthesis" rel="noreferrer">Big Bang nucleosynthesis</a> and the <a href="https://en.wikipedia.org/wiki/Chronology_of_the_universe" rel="noreferrer">chronology of the Universe</a>.</p>

CC BY-SA 4.0
2021-04-14T12:18:38.960Z
According to this article https://journals.aps.org/prd/abstract/10.1103/PhysRevD.75.087304 , big bang nucleosynthesis yielded about 1 oxygen nucleus per 4 x 10^19 protons.
DavePhD
CC BY-SA 4.0
2021-04-14T20:54:48.023Z
@DavePhD : Their [preprint](https://arxiv.org/pdf/astro-ph/0702090.pdf) only has $<2.7\times 10^{-20}$ of ${}^{16}$O/H (from Table I).  Did their result shift by a factor of $20$ between 23 April 2007 (the arXiv v2) and 23 April 2007 (Phys. Rev. D)?
Eric Towers
CC BY-SA 4.0
2021-04-18T13:25:41.413Z
@EricTowers no, 1/(2.7 × 10^(-20)) = ~4 x 10^19 .  I just worded my statement in terms of the reciprocal, and rounded to 1 digit.  The paper gives 3 values in table 1 (1.8, 2.7 and 2.7 × 10^(-20)) like the preprint.
DavePhD
CC BY-SA 4.0
2021-04-13T15:03:28.060Z
2021-04-13T15:03:28.060Z
Warrick
<p>So, the big bang started 13.7 billion years ago, and for the next 380,000 years, the universe expanded and cooled, so atoms could start forming later on. 13,685,000,000 years ago, the early universe was too hot and dense for liquid water to form. So, the answer is <em>NO</em>, liquid water could not form about 15 million years after the big bang.</p>
<p>Hoping this was helpful, I'd like to say something afterwards; Welcome to Astronomy Stack Exchange, @Cerelic!</p>

CC BY-SA 4.0
2021-04-16T14:16:36.660Z
I specified down to the fact that you're new to _Astronomy_ Stack Exchange, but not other Stack Exchange sites. Don't worry, it happens to me all the time! I'm new _here_, but not to Physics, Mathematics, or Academia Stack Exchange.
Questioner
CC BY-SA 4.0
2021-04-16T14:10:44.770Z
2021-04-16T14:10:44.770Z
Questioner
<p>Let's interpret your question to be about whether the conditions would permit blobs of water to remain liquid, whether or not water existed yet. And the answer is No, because the pressure was by then far too low. Basically, space was already a vacuum, just not as hard a vacuum as intergalactic space is now.</p>
<p>It is appealing to imagine an era when the universe was simultaneously dense enough and cool enough for liquid water (and thus perhaps humans) to exist. But alas it is not so. At the time of the creation of the cosmic microwave background, around 370 thousand years after the Big Bang, the temperature was around 3,000K, but the pressure was around <span class="math-container">$10^{-17}$</span> atmospheres (see the Wikipedia article <a href="https://en.wikipedia.org/wiki/Chronology_of_the_universe" rel="noreferrer">Chronology of the Universe</a>, and search for &quot;Recombination&quot;).</p>

CC BY-SA 4.0
2021-04-14T01:14:23.453Z
This is a useful answer - at very low pressures (below about 0.006 atmospheres), only the solid and gas phases of water exist.  So even in our own solar system, in the space between Earth and Venus for example, the equilibrium temperature is between 0 and 100 C, but liquid water cannot exist there because of the low pressure.
Eric Jensen
CC BY-SA 4.0
2021-04-14T12:57:22.003Z
Okay, so not 15 million years after Big Bang. Was there at some earlier point a combination of pressure and temperature to permit liquid water? I think it would make the answer much better if you can answer that too!
Daniel Darabos
CC BY-SA 4.0
2021-04-14T21:34:27.787Z
@DanielDarabos It seems by implication that the answer is no... if the temperature was 3000K at 370k years at 10E-17 atmospheres at it would seem both temperature and pressure could only drop from that point, the pressure is already too low while the temperature is still way too high.
Michael
CC BY-SA 4.0
2021-04-14T22:10:53.007Z
Awesome explanation, thanks!
Daniel Darabos
CC BY-SA 4.0
2021-04-15T12:06:55.553Z
A somewhat literal take on "The Mists of Time" here!
Rowan
CC BY-SA 4.0
2021-04-15T18:58:50.750Z
But doesn't this answer assume the universe was completely homogenous at that time? Shouldn't gravitational effects make for the possibility of much higher density pockets?
stix
CC BY-SA 4.0
2021-04-15T20:09:23.467Z
Pockets too small to have significant gravity would disperse due to internal pressure, and pockets with significant gravity would rather quickly collapse into stars.
Mark Foskey
CC BY-SA 4.0
2021-04-16T19:28:27.193Z
@MarkFoskey - I'm failing to understand your last comment.  There was no oxygen, and there was an extreme level of homogeneity at 370k years.  But we've waved those obstacles away.  So why can't we we wait until the ambient temperature is favorable and take a few zettatons of liquid water (i.e., an Earth sized mass), mostly compressed to a planet sized volume surrounded by the inevitable water vapor atmosphere and let it hang in space till it freezes as the Universe cools down?
Jirka Hanika
CC BY-SA 4.0
2021-04-16T20:54:50.283Z
My understanding of the OP's idea was that maybe liquid water could have existed in small quantities in space. It was really a question about the termperature/pressure properties of the cosmic medium. Absolutely, if you took present-day Earth and time-traveled it back to the 15M-year epoch, then water should be able to exist. You could talk about the heat balance with a CMB at room temperature; not sure if it would need to be lower. But my answer is for small free-floating blobs of water. Maybe I'll clarify that.
Mark Foskey
CC BY-SA 4.0
2021-04-13T23:36:18.397Z
2021-04-15T00:48:08.447Z
2021-04-15T00:48:08.447Z
Mark Foskey
<p>Around 15 million years after the Big Bang, the ambient temperatures was about <span class="math-container">$24^\circ {\rm C}$</span>, which is in a range where water could be liquid. Could liquid blobs of water be existent then?</p>
<p>PS: I am <em>not</em> talking about water on the surface of any solid planet.</p>

CC BY-SA 4.0
2021-04-13T13:56:21.783Z
Finding enough oxygen to make water might be problematic...
Jon Custer
CC BY-SA 4.0
2021-04-13T14:33:57.427Z
There probably was no oxygen in the early Universe, until stars formed.
WarpPrime
CC BY-SA 4.0
2021-04-13T16:16:41.223Z
The Wikipedia BBN article has a link to [Standard big bang nucleosynthesis and primordial CNO Abundances after Planck](https://arxiv.org/abs/1403.6694), which uses simulations to calculate a BBN CNO/H ratio (by number) of $\approx (5-30) × 10^{-15}$, and *possibly* as high as $10^{-13}$. So there was (probably) *some* oxygen before stars existed but it was spread very thinly through the predominant H & He.
PM 2Ring
CC BY-SA 4.0
2021-04-13T16:20:34.653Z
However, even if some water was formed in that era, it wouldn't be in liquid form: liquids tend to evaporate at low pressure. See https://en.wikipedia.org/wiki/Phase_diagram
PM 2Ring
CC BY-SA 4.0
2021-04-14T07:30:20.627Z
Note that temperature in this context does not really mean the same as the temperature you measure in your oven or garden.
gerrit
CC BY-SA 4.0
2021-04-14T16:06:11.547Z
The pressure war far below the triple point of the water, so the very little water which existed, was either vapor or ice (second is unlikely because there was not enough to form crystals, due to the very little O2).
peterh
CC BY-SA 4.0
2021-04-14T16:22:59.937Z
Very unlikely but *maybe* possible that some higher pressure pockets had existed, either by gravitational fluctuations or by some different, possibly unknown phenomena. Too much surely not (it is known that the Universe was "flat" at the time). There, if also the temperature was correct, maybe some little liquid water could have imho existed. But there were not stars yet, afaik the Universe at the time is expected to be a roughly same presure & temperature, filled out mostly with H, with a little He.
peterh
CC BY-SA 4.0
2021-04-15T16:15:09.020Z
I took your question to mean, if a blob of water happened to exist in space, how long would it persist? I would be interested to hear opinions on how long the core of a, say, 2 light year diameter sphere of water would remain livable (to fishy aliens).
MartinB
CC BY-SA 4.0
2021-04-16T05:12:10.030Z
@MartinB Thinking about the mass of a 2LY sphere of water, I suspect the answer is "not long enough for them to suffer". Nothing that heavy stays livable, or liquid, or water, for very long.
G_B
<space><big-bang-theory><temperature><water>
Could liquid water have existed in open space 15 million years after the Big Bang?
Cerelic
# Could liquid water have existed in open space 15 million years after the Big Bang?

(Asked by: username_0 on 2021-04-13)

Around 15 million years after the Big Bang, the ambient temperatures was about $24^\circ {\rm C}$, which is in a range where water could be liquid. Could liquid blobs of water be existent then?

PS: I am *not* talking about water on the surface of any solid planet.

**Tags:** space, big-bang-theory, temperature, water
> **Comments:**
> **username_1**: Finding enough oxygen to make water might be problematic...  
> **username_2**: There probably was no oxygen in the early Universe, until stars formed.  
> **username_3**: The Wikipedia BBN article has a link to [Standard big bang nucleosynthesis and primordial CNO Abundances after Planck](https://arxiv.org/abs/1403.6694), which uses simulations to calculate a BBN CNO/H ratio (by number) of $\approx (5-30) × 10^{-15}$, and *possibly* as high as $10^{-13}$. So there was (probably) *some* oxygen before stars existed but it was spread very thinly through the predominant H & He.  
> **username_3**: However, even if some water was formed in that era, it wouldn't be in liquid form: liquids tend to evaporate at low pressure. See https://en.wikipedia.org/wiki/Phase_diagram  
> **username_4**: Note that temperature in this context does not really mean the same as the temperature you measure in your oven or garden.  
> **username_5**: The pressure war far below the triple point of the water, so the very little water which existed, was either vapor or ice (second is unlikely because there was not enough to form crystals, due to the very little O2).  
> **username_5**: Very unlikely but *maybe* possible that some higher pressure pockets had existed, either by gravitational fluctuations or by some different, possibly unknown phenomena. Too much surely not (it is known that the Universe was "flat" at the time). There, if also the temperature was correct, maybe some little liquid water could have imho existed. But there were not stars yet, afaik the Universe at the time is expected to be a roughly same presure & temperature, filled out mostly with H, with a little He.  
> **username_6**: I took your question to mean, if a blob of water happened to exist in space, how long would it persist? I would be interested to hear opinions on how long the core of a, say, 2 light year diameter sphere of water would remain livable (to fishy aliens).  
> **username_7**: @MartinB Thinking about the mass of a 2LY sphere of water, I suspect the answer is "not long enough for them to suffer". Nothing that heavy stays livable, or liquid, or water, for very long.  

---

## 3 answers

### Answer by username_12 on 2021-04-13. Score: 48 | Accepted answer

Let's interpret your question to be about whether the conditions would permit blobs of water to remain liquid, whether or not water existed yet. And the answer is No, because the pressure was by then far too low. Basically, space was already a vacuum, just not as hard a vacuum as intergalactic space is now.

It is appealing to imagine an era when the universe was simultaneously dense enough and cool enough for liquid water (and thus perhaps humans) to exist. But alas it is not so. At the time of the creation of the cosmic microwave background, around 370 thousand years after the Big Bang, the temperature was around 3,000K, but the pressure was around $10^{-17}$ atmospheres (see the Wikipedia article [Chronology of the Universe](https://en.wikipedia.org/wiki/Chronology_of_the_universe), and search for "Recombination").

> **Comments:**
> **username_13**: This is a useful answer - at very low pressures (below about 0.006 atmospheres), only the solid and gas phases of water exist.  So even in our own solar system, in the space between Earth and Venus for example, the equilibrium temperature is between 0 and 100 C, but liquid water cannot exist there because of the low pressure.  
> **username_14**: Okay, so not 15 million years after Big Bang. Was there at some earlier point a combination of pressure and temperature to permit liquid water? I think it would make the answer much better if you can answer that too!  
> **username_15**: @DanielDarabos It seems by implication that the answer is no... if the temperature was 3000K at 370k years at 10E-17 atmospheres at it would seem both temperature and pressure could only drop from that point, the pressure is already too low while the temperature is still way too high.  
> **username_14**: Awesome explanation, thanks!  
> **username_16**: A somewhat literal take on "The Mists of Time" here!  
> **username_17**: But doesn't this answer assume the universe was completely homogenous at that time? Shouldn't gravitational effects make for the possibility of much higher density pockets?  
> **username_12**: Pockets too small to have significant gravity would disperse due to internal pressure, and pockets with significant gravity would rather quickly collapse into stars.  
> **username_18**: @MarkFoskey - I'm failing to understand your last comment.  There was no oxygen, and there was an extreme level of homogeneity at 370k years.  But we've waved those obstacles away.  So why can't we we wait until the ambient temperature is favorable and take a few zettatons of liquid water (i.e., an Earth sized mass), mostly compressed to a planet sized volume surrounded by the inevitable water vapor atmosphere and let it hang in space till it freezes as the Universe cools down?  
> **username_12**: My understanding of the OP's idea was that maybe liquid water could have existed in small quantities in space. It was really a question about the termperature/pressure properties of the cosmic medium. Absolutely, if you took present-day Earth and time-traveled it back to the 15M-year epoch, then water should be able to exist. You could talk about the heat balance with a CMB at room temperature; not sure if it would need to be lower. But my answer is for small free-floating blobs of water. Maybe I'll clarify that.  

---

### Answer by username_8 on 2021-04-13. Score: 21

As others have mentioned in the comments, there wouldn't have been any oxygen to form water. Soon after the Big Bang, the protons were hot or dense enough to fuse up to helium and some lithium but nothing heavier. Heavier elements were eventually fused in the first stars and partially dispersed in space by their winds and when they exploded as supernovae, but the first stars probably didn't form for a few hundred million years after the Big Bang.

For more information, have a look at the Wikipedia articles on [Big Bang nucleosynthesis](https://en.wikipedia.org/wiki/Big_Bang_nucleosynthesis) and the [chronology of the Universe](https://en.wikipedia.org/wiki/Chronology_of_the_universe).

> **Comments:**
> **username_9**: According to this article https://journals.aps.org/prd/abstract/10.1103/PhysRevD.75.087304 , big bang nucleosynthesis yielded about 1 oxygen nucleus per 4 x 10^19 protons.  
> **username_10**: @DavePhD : Their [preprint](https://arxiv.org/pdf/astro-ph/0702090.pdf) only has $<2.7\times 10^{-20}$ of ${}^{16}$O/H (from Table I).  Did their result shift by a factor of $20$ between 23 April 2007 (the arXiv v2) and 23 April 2007 (Phys. Rev. D)?  
> **username_9**: @EricTowers no, 1/(2.7 × 10^(-20)) = ~4 x 10^19 .  I just worded my statement in terms of the reciprocal, and rounded to 1 digit.  The paper gives 3 values in table 1 (1.8, 2.7 and 2.7 × 10^(-20)) like the preprint.  

---

### Answer by username_11 on 2021-04-16. Score: 1

So, the big bang started 13.7 billion years ago, and for the next 380,000 years, the universe expanded and cooled, so atoms could start forming later on. 13,685,000,000 years ago, the early universe was too hot and dense for liquid water to form. So, the answer is *NO*, liquid water could not form about 15 million years after the big bang.

Hoping this was helpful, I'd like to say something afterwards; Welcome to Astronomy Stack Exchange, @Cerelic!

> **Comments:**
> **username_11**: I specified down to the fact that you're new to _Astronomy_ Stack Exchange, but not other Stack Exchange sites. Don't worry, it happens to me all the time! I'm new _here_, but not to Physics, Mathematics, or Academia Stack Exchange.  

---

