When did alien life evolve - just after the Big Bang or not?
Earthlings may be extreme latecomers to a universe full of life, with a great number of alien microbes possibly emerging on exoplanets beginning just 15 million years after the Big Bang, new research suggests. Astrobiologists keen on solving the mystery of the origin of life in the universe, as a rule, look for planets in habitable zones around stars, which are also known as Goldilocks zones. And what is needed for life to exist, as we know, is liquid water.
However, even exoplanets that orbit far beyond the habitable zone may have been able to support life in the distant past, warmed by the relic radiation left over from the Big Bang that created the universe 13.8 billion years ago, Harvard astrophysicist Abraham Loeb says.( The Big Bang to Now in 10 Easy Steps)
After the Big Bang occurred, the cosmos was a far hotter place that was filled with sizzling plasma. The first light produced by this plasma is the cosmic microwave background (CMB) that we can observe today, which dates from about 389,000 years after the Big Bang.
Now the CMB is freezing cold - around minus 454 degrees Fahrenheit (minus 270 degrees Celsius).
It is the CMB’s heat that would have allowed water to remain liquid on ancient exoplanets, Loeb said.
The only question here is whether planets – and especially rocky planets – could already have formed at that early epoch, that is, 15 million years ago.
According to the standard cosmological model, the formation of the very first stars out of hydrogen and helium started tens of millions of years after the Big Bang.. Heavy elements, which are necessary for planet formation, were not around at that time.
But Loeb says that rare “islands” loaded with denser matter may have existed in the early universe, and that massive, short-lived stars could have formed in them earlier than expected.
Loeb argues, it would have possible for the very first rocky planets to have liquid water on their surface for several million years.
Loeb says that it is possible to test his theory by searching in the Milky Way Galaxy for planets around stars with almost no heavy elements.
Based on his findings, Loeb also challenges the idea in cosmology known as the anthropic principle. This concept attempts to explain the values of fundamental parameters by arguing that humans could not have existed in a universe where these parameters were any different than they are. Therefore, intelligent beings are supposed to exist only in a universe like ours, which is tuned for life.
For instance, Albert Einstein identified a fundamental parameter in his theory of gravity. This constant is now thought to account for the accelerating expansion of the universe.
Also known as dark energy, this constant can be interpreted as the energy density of the vacuum, one of the fundamental parameters of our universe.
Anthropic reasoning suggests that there might be different values for this parameter in different regions of the multiverse.
Loeb disagrees. He says that life could have emerged in the early universe even if the cosmological constant was a million times bigger than observed.
Edwin Turner, a professor of astrophysical sciences at Princeton University, who was not involved in the new study, found the research “very original, stimulating and thought-provoking”.
Astrophysicist Joshua Winn of the Massachusetts Institute of Technology, who did not take part in the study either, agrees.
Voice of Russia, Space.com
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