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Comment by pfdietz | Hacker News Reader

Now justify your implicit assumption that the chance life arises on a suitable planet is at least 1 in 10^22.

It is at least 1 in 10^22 because we have very strong evidence of one habitable planet

Edit: See https://en.m.wikipedia.org/wiki/Earth

The chance of a habitable planet happening could just as easily be 1 in 10^10000000000000000000000000, and it was just a freak occurrence it happened at all. Just because something happened once doesn't tell you much about the odds of it occurring.

Why 10^22, and not 10^10, or 10^40, or whatever? The number has to come from somewhere. This should be a strong clue your logic is defective.

This earth place sounds preposterous!

I'm supposed to believe the planet's alpha predators willing make themselves subservient to smaller, but more furry beta predators?

Anything goes, when you're made of meat :-)

Wait...are you asking me to believe in thinking meat!?

To be fair, we are working very hard on changing it to uninhabitable

>uninhabitable

*for humans

If you get hit by a bus on a second crosswalk that doesn’t mean the chance of it was 50%.

The point is we don’t know either way. Earth may or may not be a “Goldilocks” planet.

Also, the numbers above are based on the observable universe. We have no idea how big the universe is outside that region. It could be infinitely large.

Right. So, the argument "10^22 is a lot so we can't be alone" is a non sequitur.

I understand it to be a counterargument to the “Goldilocks” non-sequitur.

A root fact of my philosophy is the unrefutable claim that I exist, and am alive, so the 1 in 10^22 seems very reasonable.

Not 1 in 10^21, or 1 in 10^23? Where exactly is this number coming from? You are implicitly assuming a probability that life can arise. Don't you think that number has to be informed by an actual theory of how life arises, not inferred just from your own existence?

And in fact, you can conclude nothing from your own existence. Observer selection bias.

What an oddly pedantic comment.

10^21, 10^22 and 10^23... Whichever number, the point that the parent poster was making doesn't change at all.

>You are implicitly assuming a probability that life can arise.

What are you suggesting? We're all actually not alive? Come on.

No, it's not oddly pedantic. It's more an expression of anger, because this sort of argument is common among SETI people. It's a very common error: there's lots of opportunities for life to arise, therefore life must be common in the universe. And this is utter bullshit. Probability does not work that way!

> there's lots of opportunities for life to arise, therefore life must be common in the universe. And this is utter bullshit.

Why anger? And will you expand on why this is utter bullshit? In what way does probability not work this way? You are making strong assertions without expanding on why you believe those assertions.

Your assertion also goes against some pretty big names in the field; not that big names are automatically trustworthy, but they do seem to carry more weight than a random HN comment (no offense).

The argument that gets my goat is basically this: "if N is large enough, then for any probability p > 0, N p > 1." And that's clearly false.

The SETI people making this busted argument are implicitly assuming p, the chance that life arises on a suitable world, is not "too small". And there is no basis for making that assumption.

I don't think the common form of argument is that because N is large enough, life must exist.

The argument is generally that scale and probability favor the existence of intelligent life, assuming Earth is not somehow exceptional in the universe.

Assuming Earth is exceptional seems just as problematic.

Welcome to the Fermi paradox.

And for any N, if p is small enough, other life is very unlikely to exist.

Why are you holding p fixed and allowing N to increase? You are implicitly assuming N is in that regime where N > 1/p. That's just assuming p > 1/N, and there's no good reason to make that assumption.

I sympathize -- I've argued your side of this many times. I won't jump in today, but I just wanted you to know your words aren't falling on entirely deaf ears.

I think observer selection falls into a cognitive blind spot many people have.

This fallacy has always bothered me so thank you for stating it so well!

> I don't think the common form of argument is that because N is large enough, life must exist.

The comment that started this thread: "That's 10^22 opportunities to get it right. We can't possibly be alone."

On all of the Goldilocks planets we have so far been able to image with the resolution needed to determine the presence of life, we have determined the presence of life.

That is not mathematically rigorous, but it is, from the Bayesian perspective, enough to move the needle.

Observer selection bias blows that argument out of the water. Ask yourself: if life were extremely rare, what would be different here on Earth? Nothing, because life has to have started on Earth for us to be here to be thinking about it.

> That is not mathematically rigorous, but it is, from the Bayesian perspective, enough to move the needle.

That is obviously false; zero observations will never cause a Bayesian adjustment.

As far as N is smaller than the available combinations, the hypothesis is probable.

This thread comes across as bickering, and detracts from OP's original euphoric "wow" message.

Orthogonal and bickering, but I find it interesting. I can keep two thoughts going at once. Sort of.

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