this post was submitted on 31 Mar 2024
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Showerthoughts
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I'd think of it like this...
The universe is ~13 billion years old. However for the first few billion years, the universe was a wildly dangerous place to live. A sea of Hydrogen generating Supermassive stars, exploding within just 100,000s/millions of years, and generating many of the heavy elements that exist today. Even if a planet could form in these conditions, chances are it would've been annihilated before life could develop.
I don't know exactly when the universe started to "stabilise", but let's say there is ~10 billion years of time that a planet like Earth could've formed.
The Earth is ~4.5 billion years old.
Single-celled life arose ~3-4 billion years ago.
Complex multi-cellular life arose only ~500 million years ago during the Cambrian Explosion - so much needs to happen for complex life to arise that it could take a long time even in the best case scenario.
Humans arose only ~100,000 years ago... albeit had the dinosaurs not been around for so long, we could have come about maybe 10s of millions of years earlier.
From there basically everything comes down to how long it takes for a race to figure out farming, adopt a sedentary lifestyle that allows development of non-survival related disciplines, and to industrialise.
In the case of humans, the oldest cultures are around 10,000 years old, and we industrialised only a couple hundred years ago.
If we make the assumption that we're not exceptional amongst any intelligent lifeforms, then it would make sense to assume that it takes roughly 3-5 billion years for a race to reach where we are now.
That means we could be late to the party, and everyone else has already wiped themselves out, but it's just as likely we're right in the thick of it but just too far away from anyone else in our cohort to see anything, and vice versa.
It's basically just the Fermi Paradox - and the only way we get an answer is when the void answers back.
Didn’t we just get new evidence from JWST+Hubble that the universe may be as much as twice as old as we thought - or ~26bn years?
That relies on the "tired light" hypothesis being correct. It solves a number of problems, in a more elegant way. However, it also requires explanations for some new mismatches. E.g. why the cosmic background radiation doesn't seem to have aged the same way.
It's a theory that can't be immediately dismissed, which makes it interesting, but it's far from proven. Scientists can now look for details that would differ between the 2 models, and so help clarify what is happening.
I wouldn't know anything about that - but it certainly sounds interesting, including what @cynar said
There's also a period of time just as expansion gets going for a few million years where literally everywhere, except the exploding and burning stars, was the correct temperature for water to be liquid. Life may have gotten as far as some basic bacteria chilling everywhere out in "space" which may be why it seems to have been on Mars, back when Mars had an atmosphere and liquid water.