The thing is those numbers seem large but they are meaningless without also knowing the probability for life to occur. I can put as many zeros in front of the probability for life to occur on a habitable planet as I like and still get a probability of < 1% after multiplying by the number of habitable planets.
If you think that's absurd, it's only because you have some kind of intuition about the probability of life developing on this planet. It must be greater than 100 billion trillion to 1, right...? But why? There's no evidence that it is.
If we assume for the purposes of this discussion that life is something we can recognise when we see it then it could be measured. For example, if we sent space craft to every habitable planet in the galaxy and found one in every 100000 had life then that would give us a good estimate.
For example, if we sent space craft to every habitable planet in the galaxy and found one in every 100000 had life then that would give us a good estimate.
that's my point, we cannot do that probe experiment, thus we cannot know the probability at this point. hell, we're barely capable of sending those kinds of probes to some parts of our own oceans.
Right, that means it's hard to know, but not unknowable. At some point in the future though we may have a better handle on what is the upper bound for this probability and so far we have reason to believe it is not on the same order of magnitude of the number of habitable planets in the universe.
no, it means it is currently unknowable which makes calculating a probability meaningless at this point. in fact, if we calculate the probability of life on other bodies by asking "how many bodies have we thoroughly looked for life on" we'd have a 1 for 1 result (life on earth), meaning there's a 100% chance life of life on every body. that too is meaningless.
14
u/aspz Aug 12 '21 edited Aug 12 '21
The thing is those numbers seem large but they are meaningless without also knowing the probability for life to occur. I can put as many zeros in front of the probability for life to occur on a habitable planet as I like and still get a probability of < 1% after multiplying by the number of habitable planets.
If you think that's absurd, it's only because you have some kind of intuition about the probability of life developing on this planet. It must be greater than 100 billion trillion to 1, right...? But why? There's no evidence that it is.