> Statistics is a very precise science. Can you show your work or is it just a gut feeling?
In my case, my gut feeling, but is it so unlikely?
As mentioned in "Cosmos: Possible Worlds", planets may go through a "habitable zone", which is the window in which they are just the right distance from just the right star, and they have the right elements in their surface or whatnot. And then just the right random events have to happen and there's the spark of life. And then a gazillion extinction events must be averted, at times when the Tree of Life (to use the metaphor from Cosmos) is at its most fragile, when all of life could be cut down before its prime.
It sounds unlikely for any single planet, any single star system, any single galaxy, etc. But on the grand scale of the universe, it cannot be that nowhere else but here on Earth did this happen.
I don't know if this is statistics. It surely is gut feeling. But I think it's the right kind of gut feeling...
> it cannot be that nowhere else but here on Earth did this happen.
> I don't know if this is statistics. It surely is gut feeling.
It's possible that life emerging is so unlikely that it has never happened before anywhere even if it could happen again. We do not have the data to establish how likely and in fact we don't even have enough data to fill in all the gaps of how life on earth emerged in the first place. Our gut feelings are likely heavily influenced by science fiction or other priors and can't be trusted for knowledge but we are as a species very good at deluding ourselves into thinking we know things that we don't.
But that's it. Life doesn't seem so unlikely, does it? There are things we still don't understand about it, but we understand some, and it's not magic. It can happen, given the right conditions, much like mold may grow on a piece of bread under the right conditions.
What's difficult to comprehend is the immense vastness of the universe. It seems unlikely that nowhere else did the preconditions for life arise, and in fact, it seems likely that they must have arisen in multiple places. Immensely many places, in fact. Considered like that, it's more unlikely that life didn't appear anywhere else but in this Pale Blue Dot.
We look at our planet, and all that had to happen for those first lifeforms to come into existence, and it seems so unlikely... but not impossible. And we're playing with a lot of dice here! Very hard not to roll a few sixes with a bag of dice so large.
> There are things we still don't understand about it, but we understand some, and it's not magic.
> What's difficult to comprehend is the immense vastness of the universe.
We know a whole lot about ways life changes once it's there but we haven't observed life emerging from non-life and our hypotheses for how life emerged on earth has more holes than swiss cheese and it doesn't have to be magic in order to be exceedingly improbable. And magnitudes work in both ways, if it is sufficiently improbable for life to emerge, let's say 1 chance in 1E100 against then even if you had dice rolls in proportion to all the subatomic particles in the universe (~1E80) multiplied by the number of seconds since the big bang (~4E17) then it would still be about 3 orders of magnitude against the likelihood of life emerging even once. In this scenario if the probability was 4E97 then we'd expect for life to have emerged once. Until we have the data to infer what the probability actually is we can't determine which scenario is the case.
> but we haven't observed life emerging from non-life
But our laboratory is very, very small, so that proves little.
And we know life emerged at least once, and it doesn't seem particularly improbable. That's what I mean by "not magic"; not that we understand every little step, but we have some idea.
I don't think it's scifi to believe it's unlikely only Earth has sparked life. The one thing that is unlikely is that we will ever witness life anywhere else, but that's a different problem.
