I don't know enough to know if the range you specify is right, but I agree that it is silly to say 10^-22 is a ridiculously small number. For one thing, when ta

I don't know enough to know if the range you specify is right, but I agree that it is silly to say 10^-22 is a ridiculously small number. For one thing, when talking about the size of probabilities, we should talk about the size of the exponent. -22 is not a ridiculously small number. People base the idea that there should be other life in the universe on the fact that life developed at least once, which is here on earth. The odds are it would happen either 0 times or many times, but not exactly once. This argument is reasonable if there is one universe. Another scenario is that there is some god awful large number of universes (for round numbers let's say 10^1000 raised to the 10^10000 power, which would be a huge underestimate), and that most of these universes contain no life, because the odds of life developing are also very, very small. We ARE special in that we are viewing one of the small fraction of universes that has life, because if it didn't we wouldn't be viewing it. This allows for life to exist exactly once in our universe. There could also be universe where life developed independently more than once, but the odds of us being in that universe are very small relative to the odds of being in a universe with one life. But how would there be many universes? Here is one possibility that is surely controversial. In quantum mechanics, things happen in parallel. Is that electron spin up or spin down? It is both, but the electron in one state is not influenced by the electron in the other state. Each exists wholly on its own. This is true whether you believe the Stockholm or the Many Worlds interpretation of quantum mechanics. These two cases only differ when some special life form makes an observation, in which cases something very dramatic happens in the Stockholm interpretation (which is observationally indistinguishable from the "nothing different" that happens in the Many Worlds interpretation). If we think about the simplest form of life that can not make observations rather than looking for human-like life, the distinction between Stockholm and Many Worlds is mute. These parallel states of the system form our many universes, some that contain life and some that do not.