Extraterrestrial Life Probability

On Earth, it took something over half the available time for it to happen, and during that time, several events nearly rolled back complex life, so it doesn't seem inevitable. In the universe as a whole, it would seem much more likely, unless you think the Fermi Paradox indicates that there's probably at least one difficulty that takes literally astronomical odds to surmount.

Nice work of science fiction. It is impossible to estimate the probability of these events with a sample size of one. It likely took billions of years for our planet to reach the right temperature and composition for life to form. It's probable that life readily forms given the right conditions. In my opinion, it makes more sense that it is rare for a planet to develop the right conditions for life. That doesn't really matter much given there are 700 quintillion planets in our universe

Ok, we don't know how likely life is to evolve in the universe. It could range from impossibly hard (though it cant actually be that, because we exist) to easy enough that it has occurred many times. Of all those possibilities, what difficulty range would result in it occurring once (on earth), but never again - despite the billions and billions of planets that exist. A very, very fine tuned difficulty - or to put it another way, the earth would need to be super,super unique, to be the only

I think that's only true assuming no other life has appeared in any other place of the universe.

The space is big, but time is vast too. There was a time in the universe when the entire universe averaged a temperature conducive to life and there was oxygen, carbon, and other crucial elements available (although not as plentiful as now). Life could have formed then, and largely died out. In fact life may only pop up rarely in both space and time, so rarely that it’s unlikely two planets have life within a detectable distance at the same time. In fact it’s even possible a highly advanced civi

"Chance of life forming from non life * age of the universe * number of stars * the chance a star has an earth like planet, is far from zero"You have no proof for this, and things can well be the other way round. Letn = age of the universe * number of stars * the chance a star has an Earth like planetn is a number that we currently have a pretty good guess at. Let p = chance of life forming from non life on Earth-like planet within a given year. We are basically clu

One thing that gives me pause for thought: even here on Earth, we are all, likely, descendants of a single organism: https://en.wikipedia.org/wiki/Last_universal_common_ancestor .It doesn't necessarily mean that the 0-1 creation of life happened exactly once on Earth (maybe it happened many times but the other lineages died out), but I think it makes this argu

Given the gaps in our knowledge of early life, a definite statement in either direction is unlikely to be in the offing. However, terrestrial life is decidedly unlikely. Life is decidedly unlikely, and no one has so far suggested an even remotely plausible mechanism for abiogenesis on Earth. This means if you are betting, an extraterrestrial origin is the safe bet; if the odds of abiogenesis are so slim, while life once formed is tenacious and hardy enough to travel through space, it is more lik

Is that a reasonable assumption to make? I don't think we have any evidence of other places we look being "largely the same" with respect to life conduciveness. It took billions of years for our own planet to achieve multicellular life, which is a significant fraction of our best estimate of the lifetime of the entire universe up to this point.

Or maybe not. If you consider how improbable is the origin of life on the earth then maybe it's not even enough planets in the observable universe to start a life. But the universe is much greater than its observable part.