In the redshift range 100<(1+z)<137, the cosmic microwave background (CMB) had a temperature of 273-373K (0-100 degrees Celsius), allowing early rocky planets (if any existed) to have liquid water chemistry on their surface and be habitable, irrespective of their distance from a star. In the standard LCDM cosmology, the first star-forming halos within our Hubble volume started collapsing at these redshifts, allowing the chemistry of life to possibly begin when the Universe was merely 10-17 million years old. The possibility of life starting when the average matter density was a million times bigger than it is today argues against the anthropic explanation for the low value of the cosmological constant.
Metadata: arXiv. Abstracts retain their original authors’ rights.
In the conversation
Original HN comments, with labels from simple text rules. A label describes the whole comment and may miss context or irony. Read the discussion to make up your own mind. About the labels
That gets into astrobiology. Theoretically life could have started as soon as its basic ingredients were ready. So not until things had cooled down a bit after the Bang, when there were heavier elements than hydrogen and helium; and some kind of land and water.
> In the redshift range 100 . (1 + z) . 137, the cosmic microwave background (CMB) had a temperature of 273–373 K (0-100◦C), allowing early rocky planets (if any existed) to have liquid water chemistry on their surface and be habitable, irrespective of their distance from a star.
> In the standard ΛCDM cosmology, the first star-forming halos within our Hubble volume started collapsing at these redshifts,allowing…
Read the full comment
the chemistry of life to possibly begin when the Universe was merely 10–17 million years old.
From: The Habitable Epoch of the Early Universe - https://arxiv.org/abs/1312.0613
In comparison, our beloved sun is estimated to have been born 9.2 billion years after the Big Bang, a third of the way into the universe's history so far.
> The Sun is approximately 4.6 billion years old, while the age of the universe, based on current estimates, is about 13.8 billion years.
So our solar system is not that old, relatively speaking. We're among elders, some stars are three times older than the sun.
> In the future, however, life might continue to emerge on planets orbiting dwarf stars, like our nearest neighbor, Proxima Centauri, which will endure hundreds of times longer than the sun’s.
> Ultimately, it would be desirable for humanity to relocate to a habitable planet around a dwarf star like Proxima Centauri b, where it could keep itself warm near a natural nuclear furnace for up to 10 trillion years into the future.
my favourite hypothesis for the first life is the idea that the entire universe might have been habitable for a while: https://arxiv.org/abs/1312.0613
of course, it's very unlikely, but it's such a cool idea!
> the time when the universe was at life supporting temperatures, was long before the formation of the first stars and fusion of heavier atoms than hydrogen
Stars with rocky planets during the habitable epoch "lie ∼8.5 standard deviations (σ) away on the exponential tail of the Gaussian probability distribution of initial density perturbations," though "their abundance could have been significantly enhanced by primordial non-Gaussianity."
[1] https://arxiv.org/pdf/1312.0613.pdf
This reminds me of a paper [1] where they find that... "In the redshift range 100<(1+z)<137, the cosmic microwave background (CMB) had a temperature of 273-373K (0-100 degrees Celsius), allowing early rocky planets (if any existed) to have liquid water chemistry on their surface and be habitable, irrespective of their distance from a star."
[1] https://arxiv.org/abs/1312.0613
The big bang was extremely hot; the universe now is quite cold (microwave background). It was a continuous process of cooling, implying that there was an interval where the entire universe was comfortable (there are at least a few papers on this, e.g. https://arxiv.org/abs/1312.0613 , but I like it more just as a strange thing to thing about).
I did my PhD in astrophysics, and I can tell you that the author's name has become synonymous with, shall we say, fringe ideas. I won't say crack pot because he is a legit tenured astronomer at Harvard, but I have seen his papers roundly critiqued on the merits at too many journal clubs to count. (Eg, life could have evolved in interstellar space https://arxiv.org/abs/1312.0613 ) Its a bit outrageous to claim he's Galileo and the rest of the community is the Church when he is so clearly using his tenure as a defense against the weakness, and untestability, of his ideas.
Regardless of the truth in this specific case, Avi has some very interesting ideas such as the habitable early universe.
https://arxiv.org/abs/1312.0613
The habitable epoch of the early Universe, Abraham Loeb, DOI: https://doi.org/10.1017/S1473550414000196
https://arxiv.org/abs/1312.0613 , https://www.cambridge.org/core/journals/international-journa...
>"In the redshift range 100≲(1+z)≲137, the cosmic microwave background (CMB) had a temperature of 273–373 K (0–100°C), allowing early rocky planets (if any existed) to have liquid water chemistry on their surface and be habitable, irrespective of their distance from a star. In the standard ΛCDM cosmology, the first star-forming halos within our Hubble volume started collapsing at these redshifts, allowing the chemistry of life to possibly begin when the Universe was merely 10–17 million years old. The possibility of life starting when the average matter density was a million times bigger than it is today is not in agreement with the anthropic explanation for the low value of the cosmological constant."
It is a pretty out there theory, but at one point the universe would have cooled enough from the very hot big bang origins to allow liquid water to exist everywhere, but not cooled sufficiently to cause everything to freeze.
If any rocky planets existed at the time, maybe that was the origin of life which was much more able to spread widely due to the small size of the early universe.
https://arxiv.org/abs/1312.0613
This reminds me of "The Habitable Epoch of the Early Universe" https://arxiv.org/abs/1312.0613 where it is pointed out that for some time during cosmological evolution, the universe would have been quite comfortable and rocky planets (if any existed) could have had liquid water, with no need to be in a Goldilocks zone---the whole universe was Goldilocks!
Let's not forget about the habitable epoch of the early universe [1]. There's a good 7 million years near the beginning of the universe that in principle was inhabitable to Earth-like life. None can say if the physicists of that epoch (if there were any) had enough observational evidence to foresee their quickly approaching end.
[1] http://arxiv.org/abs/1312.0613
* do actually I believe there was early-epoch life sophisticated enough to think up physical theories? No, but what does that matter?
In honor of Alan Turing's hundredth birthday, I unwisely set out some thoughts about one of Turing's obsessions throughout his life, the question of physics and free will.