The habitable epoch of the early Universe, Abraham Loeb, DOI: https://doi.org/10.1017/S1473550414000196 https://doi.org/10.1017/S1473550414000196 https://arxiv

The habitable epoch of the early Universe, Abraham Loeb, DOI: https://doi.org/10.1017/S1473550414000196 https://doi.org/10.1017/S1473550414000196 https://arxiv.org/abs/1312.0613 https://arxiv.org/abs/1312.0613 , https://www.cambridge.org/core/journals/international-journal-of-astrobiology/article/habitable-epoch-of-the-early-universe/114595C6E860A5002A9B783875602106 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."