Not sure if you are talking about the Great Filter theory or something else.
Nevertheless, for purposes of this thread, even if a Great Filter kicks in life still evolved. Evolved and killed itself but more than one planet has life (probably). And, presumably (given the timescales involved) probably all over the spectrum of evolution from microbes to space-faring societies.
“Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.” - Arthur C. Clarke
ETA: Has anyone ever postulated that we are the first sentient life in the universe and the first to go into space? Seems unlikely but maybe?
What is the chance that life arises out of inorganic materials? We don’t know - full stop. 200 million (potentially) habitable planets is a very big number. But if the odds of life arising is, say, one in a trillion the odds of life out there is almost nil.
A pithy quote to be sure, but I’ve never bought into it. In fact, neither are terrifying. If we are alone, that’s sad, maybe, but it is what it is. How can it be terrifying when we are all going to die anyway?
And if there is other life out there, that’s a cause for celebration. I don’t assume we will be alien food. Nor do a lot of folks that are running SETI.
Organic compounds are not life. The experiment was a proof of concept for abiogenesis (the origin of life from non-living matter), not a creation of life itself. Creating life is a complex process that would require many more steps to form a living organism. None of that can point to the actual odds of spontaneous life.
But they did make organic material from inorganic material. Sure, they did not poof-out a human from a lab beaker but it is certainly the first step and there is no reason to think it only ever happened on Earth.
Life as we know it probably cannot arise out of inorganic materials, but organic materials can and do form spontaneously out of inorganic ones, and they’re found not just on Earth but on Mars and other planets and have even been detected on exoplanets. Organic compounds are basically compounds with carbon-hydrogen or carbon-carbon bonds which can form long complex chains and are the basis of biomolecules and ultimately the basis of life.
So given the apparent prevalence of organic compounds beyond Earth and beyond the solar system, what would have caused life to evolve only here and nowhere else with suitable conditions? It was either some extraordinarily special condition that exists nowhere else, or some astronomically unlikely happenstance that has occurred nowhere else in the galaxy. It seems much more plausible to believe that neither of those fantastic improbabilities are true.
Nor did they poof out a single cell organism. Many scientist have been trying since then to take it to the next step - without success. That tells me it’s not an easy process. Also, IIRC, the gasses they used were incorrect for early earth.
I don’t necessarily think it only happened on earth. I was addressing the point that just because there are 200 million potential planets that there must be other civilizations out there. Without know the actual odds of life arising, the 200 million figure is meaningless.
We may not ever be able to know that but we do know it happened at least once.
When doing math tossing a zero in makes all things zero (or unanswerable…divide by zero). But we have ONE we know for certain. That changes the math and it is very unlikely, given the size of the universe and all that is in it, to suppose our planet is the only one. Possible but mathematically unlikely. Very unlikely.
I’m not disagreeing that there are probably other lifeforms out there. I’ve stated several times in this thread that I do. But we can’t know how rare it is or might be without knowing the odds of life arising. I’m pushing back against those who are postulating there are millions, of million years of ETIs that are whizzing around our galaxy like Star Trek.
A subset of one tells us only that it happened once. Show me just one more and I’ll concede ubiquity.
I think the anthropic principle is more an argument about why the universe is the way it is, with apparently fine-tuned physical constants that allow it to be stable and allow stars to form, and so on. It’s not really an argument about the prevalence of life in the universe, other than to say that if the universe were built in any other way (as perhaps some are in multiverse hypotheses) there would be no one there to observe it.
Yah…kind of a universe Zeroth Law! (if you know, you know)
But to the OP it would suggest there is nothing particularly special about the Earth either. Our universe has life in it (proof: you are reading this which circles back to the Anthropic Principle…I forget if strong or weak though). Life could form anywhere in our universe under the right conditions (which are likely to be abundant).
But note another data point is that the first organisms appeared on earth anywhere from 4.4 to 3.5 billion years ago…really pretty early, the planet was still basically a molten ball.
So the one data point we have implies the first (proto-) cell may not be the big bottleneck.
In my case, it’s only a tacit (and now explicit) acknowledgment that I don’t know enough about making either interstellar craft or self-replicating probes to make arguments about their difficulty. I’ll let those who know about what relevant work we’ve done so far in those areas make those arguments.
