First Life

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By latest estimate... how many billions of years after the Big Bang before life became possible? 2 billion yrs? 5 billion yrs? 7? And why?
 

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  • #2
Chronos
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The first life on earth is believed to have originated about 3.8 billion years ago with prokaryotes - most likely cyanobacteria. Multicellular life came much later, beginning about 2.1 billion years ago and critters we would recognize as animals - about 570 million years ago. In terms of BB time, the first life on earth arose about 10 billion years after the big event. The earth, at that time was only around 700 million years old. Obviously selection pressure was fairly subdued over the 1.7 billion years between prokaryotes and multicellulars and the 1.5 billion year span between multicellular life and animals. Of course, there is no telling how many false starts may have been sterilized by random meteorite impacts and/or tectonic cataclysms before life gained an enduring foothold. Most scientists believe the conditions on early earth were very favorable towards abiogenesis.
 
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The first life on earth is believed to have originated about 3.8 billion years ago with prokaryotes - most likely cyanobacteria. Multicellular life came much later, beginning about 2.1 billion years ago and critters we would recognize as animals - about 570 million years ago. In terms of BB time, the first life on earth arose about 10 billion years after the big event. The earth, at that time was only around 700 million years old. Obviously selection pressure was fairly subdued over the 1.7 billion years between prokaryotes and multicellulars and the 1.5 billion year span between multicellular life and animals
Thank you. But I was asking for the first life that is possible in the universe as a whole. For example. 5 billion years after the Big Bang.. can the stars already in a state that can support life? Or in other words, how old could be the oldest possible aliens in any part of the universe?
 
  • #4
davenn
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Thank you. But I was asking for the first life that is possible in the universe as a whole. For example. 5 billion years after the Big Bang.. can the stars already in a state that can support life? Or in other words, how old could be the oldest possible aliens in any part of the universe?
We can only go by what happened on Earth as our guide, since we have no idea if life even exists elsewhere in the universe
 
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We can only go by what happened on Earth as our guide, since we have no idea if life even exists elsewhere in the universe
Or by the age of the stars... how many years after Big Bang was there stars like our sun?
 
  • #6
Chronos
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I think it is fair to assume anywhere conditions similar to those of early earth are found, abiogenesis is a question of when, not if. Whether or not that life evolves into anything familiar is a different and more difficult question. Despite our impressive technology, we still do not know if simple life has ever arisen elsewhere, even within our own solar system. For that matter, we do not even know of all the niches where it ekes out a living on our own planet. To follow up th OP, since the only life for which we have evidence resides on earth, we are compelled to assume earth like conditions are a necessary prerequisite for life. That implies the need for a sun-like star, but, that may be overly constraining. A chemistry similar to earth is certainly a necessity. So we are talking water, for starters - and water is not all that scarce, We also need stellar debris to furnish a mix of 'metals' and a host star near enough to melt ice, but, not near enough to boil off all the water. You also need a star with a spectrum mild enough to avoid sterilizing whatever life may arise. These prerequisites are pretty forgiving and admit a large number of candidate stars to host a potential home for life. Such a star could arise in the universe only a handful of billions of years after the BB. So, the short of it is: life could conceivably have arisen by the time the universe was about half the age it was when the solar system. formed, but, probably not a whole lot sooner.
 
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  • #7
Drakkith
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Or by the age of the stars... how many years after Big Bang was there stars like our sun?
The very first stars, which formed between 150 million to 1 billion years after the big bang, are called population III stars and are extremely metal-poor since big bang nucleosynthesis (the creation of different elements shortly after the big bang) left much less than 1% of the matter in the universe as something other than hydrogen or helium. With almost no metals (elements other than hydrogen and helium) these early stars could not have given rise to life as we know it.

The absolute earliest that life as we know it could have arisen is probably around 1 billion years after the big bang after most of these population III stars had died off and gone supernova, spreading a small amount of heavier elements out into the universe. But that's an extremely rough estimate and should not be taken as fact. Just looking at the abundance of heavy elements, the chances for life increase as the universe ages. But since we don't know how life formed in the first place, there's no real answer to your question.
 
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  • #8
phinds
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Life forms by lightning and thunder and we first became fishes, then monkeys then humans.
This is a science forum. You should not post unsubstantiated opinion as fact.
 
  • #9
PeterDonis
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Since the OP is now on a permanent vacation from PF, this thread can be closed.
 
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