Typical galaxies the size of the Milky Way have 100 to 2,000 billion stars and could have as many as ten trillion planets.
That’s about 100^5, so one way to think of this is that if you categories these by any four properties (temperature, stability, hydration, day length) then you’d expect about 100 samples for any point in that 4D space.
So even if you believe Earth is unique along four critical metrics, there are about a hundred planets per galaxy that also have those attributes within a percentage point. If you allow some wiggle room then you have tens of thousands or even millions.
We know conditions here on Earth varied significantly more than 1% over billions of years and life survived and even thrived.
But it spent 1.5 billion years trapped in a low energy trap. Only the unusual process that brought proto-mitochondria inside bacteria made it interest. The branches that didn't follow have remained trapped with a severe limit upon their complexity.
Then use that as one of the four critical parameters.
E.g.: You might believe that some variability in conditions (hot-house Earth, iceball Earth) is required to "kick start" evolution. Okay, then simply pick out the subset of the parameter space with that amount of variability.
But we literally don't know the variability. Unlike the numbers of stars in the universe or the number of planets, which we have some statistically board observational evidence for, we have no such statistical evidence for the development of high energy microbiology. We have 1/1 examples. And we don't know if that's because it was inevitable and the eukaryotes have just outcompeted everything else or if it was exceedingly rare. It could be a coefficient of effectively 0 on the whole the thing.
That’s about 100^5, so one way to think of this is that if you categories these by any four properties (temperature, stability, hydration, day length) then you’d expect about 100 samples for any point in that 4D space.
So even if you believe Earth is unique along four critical metrics, there are about a hundred planets per galaxy that also have those attributes within a percentage point. If you allow some wiggle room then you have tens of thousands or even millions.
We know conditions here on Earth varied significantly more than 1% over billions of years and life survived and even thrived.