I don't even understand why people call it a paradox. A paradox has no obvious solution. This one has many obvious solutions, the most obvious one that the premise is faulty: perhaps life is not common at all.

I mean, we don't have any other perspective to look through. There is no other point of reference to draw from. We try to compensate by assuming that our system, planet, and species aren't particularly special and are probably about average in terms of supporting life.

We can't know or even begin to guess at what an alien civilization may do or think or how they evolved. Best we can do is assume it's probably somewhat similar to our experience. At least it's based on something factual. Anything else is really just wild speculation.

We pretty much have to assume aliens will be sort of similar to us because we haven't met any. Our experience is the only one we've got, so it's the most reasonable baseline we have. We know that aliens will probably be wildly different from us, but it's so unknowable as to be moot. Do we base our assumptions on Heinlein's writing? Asimov? Douglas Adams? Anything other than what we know from our own experience is just fanciful fiction.

But also you're not supposed to take as read the Fermi paradox, Kardashev scale, or any other ways of thinking about aliens. It's implied that they won't be anything like us. You're not supposed to take it as a literal statement that alien species will be hairless bipeds with a warlike society who think and look like us. You're supposed to follow the assumptions that statistically, we're probably not special as a species and probably any aliens we meet will have evolved along similar lines and probably will be relatable to us. Implicitly we understand that this likely is not true. We just don't know and there aren't really any options that are more reasonable or reliable than basing assumptions on the one and only planet we know that has intelligent life.

Putin and Xi fantasizing about immortality via 3D-printed organs quite starkly illustrated that many adults do not understand the difference between science and science fiction.

Yes, but as time goes to infinity there will eventually be an environment context and mutation path that will result in something that has a similar level of intelligence.

In fact, this makes the preoccupation with humans escaping a Great Filter all the more childish. Even on a single planet the species that will evolve from humans by the time Earth is swallowed by the sun will have less in common with humans than we do now with single cell organisms. Internalize that fact a little bit. Once you realize it is absurd to talk about the human species being preserved as is to the end of time, you will understand the silliness of this obsession. Cause after that point you might as well believe in a deity.

If it makes you feel warm and fuzzy inside, it suffices to hope that only single cell organisms survive the Great Filter, since given enough time it might lead to something that is as intelligent or more intelligent and kind than humans.

Embrace the silliness. The answer to "Why should we humans spread to other planets?" need only be "Why the fuck not?"

That is, unless you want to fund your rocket company. In which case you have to make people believe in a deity.

Er... No that's not a meaningful critique. There's no framework that doesn't assume it's a random process. The point is to find out how likely each step is to occur, randomly.

That doesn’t mean much. If it is actually common and the great filter is passing technological adolescence, then at least one civilisation would need to be around at least a hundred thousand years ago to be detected by us. Then, they would need to survive the great filter. We’ve only been broadcasting for 80 years or so, and any modern technology is probably indistinguishable from noise...

In other words, even if the average technological civilisation lasts 1000 years, the odds of those civilisations overlapping are nearly zero if the great filter is ahead of us. Unless civilisations manage to last much, much longer than 1,000 years (millions of years), the chance that two blips overlap in time and space closely enough to detect each other is basically negligible.

That is why the “life on Mars” point feels ominous:

- If abiogenesis is easy, the filter isn’t there.

- If the filter is later (like surviving technological adolescence), then most civilisations blink out quickly.

Which means overlapping, detectable civilisations would be vanishingly rare, explaining the silence, but also suggesting our future may be short.

Or just really hard to detect with existing technology. Combine that with the vastness of the universe, it's not a unreasonable take.

If you take the beginning of the cosmos to be 1 second ago, the point where other galaxies will be unobservable is in just a few seconds (at T+7–8). We’ve only had civilization for about 700-800 nanoseconds. You could fit hundreds or even thousands of advanced civilizations in there and they’d never know the other existed.