Could liquid water have existed in open space 15 million years after the Big Bang?

  • 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.


    Finding enough oxygen to make water might be problematic...

    There probably was no oxygen in the early Universe, until stars formed.

    The Wikipedia BBN article has a link to Standard big bang nucleosynthesis and primordial CNO Abundances after Planck, 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.

    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

    Note that temperature in this context does not really mean the same as the temperature you measure in your oven or garden.

    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).

    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.

    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 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.

  • 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, and search for "Recombination").


    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.

    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!

    @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.

    Awesome explanation, thanks!

    A somewhat literal take on "The Mists of Time" here!

    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?

    Pockets too small to have significant gravity would disperse due to internal pressure, and pockets with significant gravity would rather quickly collapse into stars.

    @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?

    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.

License under CC-BY-SA with attribution


Content dated before 7/24/2021 11:53 AM