How Old Is E.T.?
Over the years I have seen countless articles and discussions that tackle the likelihood of finding alien intelligence(s) in the Universe.
The argument is often set out like this: considering the sheer scale of the Universe, any alien civilization would likely be so remote that communication would be difficult and physical interaction impossible. That, of course, assumes that any alien technology is comparable to ours.
The discussions often go on to explain that the Universe is over 13 billion years old and so it highly probable that other civilizations have had plenty of time to evolve and develop new technology.
This conjecture is all very interesting, but in some respects a little flawed.
If I was pressed on expressing my opinion, I would certainly support the concept of a Universe where humans are not alone. However, it is also possible that we are amongst the first to emerge with any level of intelligence and technology. It may just be that our alien cousins haven't had as long to evolve as you might think.
Trying to pin down exactly when our alien neighbors emerged is a little difficult because evolution is a gradual process. If we use the point in time when Homo sapiens had an appearance consistent with those of us alive today then 'we' have been around for about 200,000 years.
Earth itself has been around for much longer, at around 4.5 billion years, which is about 35 percent the age of the Universe. If we can understand where we came from, it might be possible to infer whether we are likely to be alone or one of many emerging civilizations.
The Universe is thought to have come into existence 13.77 billion years ago, immediately after the Big Bang. The only elements present in this early Universe were hydrogen and helium and it took around 300 million years before the first 'metal poor' stars (known as Population III stars) started to appear.
Like all stars, the nuclear processes deep inside the cores of Population III stars would have worked to transform the hydrogen and helium into heavier elements.
Population III stars would have likely been massive and therefore very short-lived, maybe even as short 100 million years. As with all massive stars, their death would have been marked by a supernova explosion with the star's contents being ejected out into space. This material would then be found inside the second generation of stars known as Population II.
These stars contained heavy elements, but not the same quantities of heavy elements as we see in Population I stars like the sun. It is unlikely that rocky planets like Earth would have formed around Population II stars because of the lack of significant volumes of heavy elements.
It seems that the evolution of stars precluded the formation of rocky planets much before the appearance of Population I stars. If that is the case, and adding a generous margin for error, it looks like the first planets like Earth would have formed no earlier than 8 billion years ago.
If that is true, then it may well be that we are not necessarily the first life, but perhaps amongst the first intelligent life (as we know it) to evolve.