Doesn’t this paper boil down to “Some factors in the Drake equation are highly uncertain, and we don’t see any aliens, so those probabilities must be small after all?”
Not quite. The mean number of aliens to see is basically unchanged—the main claim that the paper is making is that a very high probability of 0 aliens is consistent with uncertainty ranges that people have already expressed, and thus with the high mean number of aliens that people would have expected to see before observations.
I’d like to rescue/clarify Mitchell’s summary. The paper’s resolution of the Fermi paradox boils down to “(1) Some factors in the Drake equation are highly uncertain, and we don’t see any aliens, so (2) one or more of those factors must be small after all”.
(1) is enough to weaken the argument for aliens, to the point where there’s no paradox anymore. (2) is basically Section 5 from the paper (“Updating the factors”).
The point you raised, that “expected number of aliens is high vs. substantial probability of no aliens” is an explanation of why people were confused.
I’m making this comment because if I’m right it means that we only need to look for people (like me?) who were saying all along “there is no Fermi paradox because abiogenesis is cosmically rare”, and figure out why no one listened to them.
The point you raised, that “expected number of aliens is high vs. substantial probability of no aliens” is an explanation of why people were confused.
Right, I think it’s important to separate out the “argument for X” and the “dissolving confusions around X” as the two have different purposes.
I’m making this comment because if I’m right it means that we only need to look for people (like me?) who were saying all along “there is no Fermi paradox because abiogenesis is cosmically rare”, and figure out why no one listened to them.
I think the important thing here is the difference between saying “abiogenesis is rare” (as an observation) and “we should expect that abiogenesis might be rare” (as a prediction) and “your own parameters, taken seriously, imply that we should expect that abiogenesis might be rare” (as a computation). I am not aware of papers that did the third before this, and I think most claims of the second form were heard as “the expected number of aliens is low” (which is hard to construct without fudging) as opposed to “the probability of no aliens is not tiny.”
But this paper does not talk about “your own parameters.” The parameters it uses are the range of published parameters. Saying that people should have used that range is exactly the same as saying that people should not have ignored the extremists. (But I think it’s just not true that people ignored the extremists.)
If interstellar panspermia is possible, “abiogenesis is cosmically rare” is not an explanation, and our Galaxy could be populated by aliens of approximately our civilisational age and the same basic genetic code.
Good point. In that case the Drake equation must be modified to include panspermia probabilities and the variance in time-to-civilization among our sister lineages. I’m curious what kind of Bayesian update we get on those...
No. It boils down to the following fact: If you take given estimates on the distribution of parameter values at face value, then:
(1) The expected number of observable alien civilizations is medium-large
(2) If you consider the distribution of the number of alien civs, you get a large probability of zero, and a small probability of “very very many aliens”, that integrates up to the medium-large expectation value.
Previous discussions computed (1) and falsely observed a conflict with astronomical observations, and totally failed to compute (2) from their own input data. This is unquestionably an embarrassing failure of the field.
I’m still not seeing a big innovation here. I’m pretty sure most researchers who look at the Drake equation think “huge sensitivity to parameterization.”
If we have a 5 parameter drake equation then number of civilizations scales with X^5, so if X comes in at 0.01, we’ve got a 1e-10 probability of detectable civilization formation. But if we’ve got a 10 parameter Drake equation and X comes in at 0.01 then it implies a 1e-20 probability. (extraordinary smaller)
So yes, it has a a huge sensitivity, but it is primarily a constructed sensitivity. All the Drake equation really tells us is that we don’t know very much and it probably won’t be useful until we can get N above one for more of the parameters.
The difference is that before people looked at the Drake equation, and thought that even with the uncertainty, there was a very low probability of no aliens, and this corrects that assumption.
Doesn’t this paper boil down to “Some factors in the Drake equation are highly uncertain, and we don’t see any aliens, so those probabilities must be small after all?”
Not quite. The mean number of aliens to see is basically unchanged—the main claim that the paper is making is that a very high probability of 0 aliens is consistent with uncertainty ranges that people have already expressed, and thus with the high mean number of aliens that people would have expected to see before observations.
I’d like to rescue/clarify Mitchell’s summary. The paper’s resolution of the Fermi paradox boils down to “(1) Some factors in the Drake equation are highly uncertain, and we don’t see any aliens, so (2) one or more of those factors must be small after all”.
(1) is enough to weaken the argument for aliens, to the point where there’s no paradox anymore. (2) is basically Section 5 from the paper (“Updating the factors”).
The point you raised, that “expected number of aliens is high vs. substantial probability of no aliens” is an explanation of why people were confused.
I’m making this comment because if I’m right it means that we only need to look for people (like me?) who were saying all along “there is no Fermi paradox because abiogenesis is cosmically rare”, and figure out why no one listened to them.
Right, I think it’s important to separate out the “argument for X” and the “dissolving confusions around X” as the two have different purposes.
I think the important thing here is the difference between saying “abiogenesis is rare” (as an observation) and “we should expect that abiogenesis might be rare” (as a prediction) and “your own parameters, taken seriously, imply that we should expect that abiogenesis might be rare” (as a computation). I am not aware of papers that did the third before this, and I think most claims of the second form were heard as “the expected number of aliens is low” (which is hard to construct without fudging) as opposed to “the probability of no aliens is not tiny.”
But this paper does not talk about “your own parameters.” The parameters it uses are the range of published parameters. Saying that people should have used that range is exactly the same as saying that people should not have ignored the extremists. (But I think it’s just not true that people ignored the extremists.)
If interstellar panspermia is possible, “abiogenesis is cosmically rare” is not an explanation, and our Galaxy could be populated by aliens of approximately our civilisational age and the same basic genetic code.
Good point. In that case the Drake equation must be modified to include panspermia probabilities and the variance in time-to-civilization among our sister lineages. I’m curious what kind of Bayesian update we get on those...
In fact, not a mine idea, I read an article about it by Panov—https://www.sociostudies.org/almanac/articles/prebiological_panspermia_and_the_hypothesis_of_the_self-consistent_galaxy_origin_of_life/
No. It boils down to the following fact: If you take given estimates on the distribution of parameter values at face value, then:
(1) The expected number of observable alien civilizations is medium-large (2) If you consider the distribution of the number of alien civs, you get a large probability of zero, and a small probability of “very very many aliens”, that integrates up to the medium-large expectation value.
Previous discussions computed (1) and falsely observed a conflict with astronomical observations, and totally failed to compute (2) from their own input data. This is unquestionably an embarrassing failure of the field.
It’s a bit more than that. I think Jan’s comment is the best summary.
I’m still not seeing a big innovation here. I’m pretty sure most researchers who look at the Drake equation think “huge sensitivity to parameterization.”
If we have a 5 parameter drake equation then number of civilizations scales with X^5, so if X comes in at 0.01, we’ve got a 1e-10 probability of detectable civilization formation. But if we’ve got a 10 parameter Drake equation and X comes in at 0.01 then it implies a 1e-20 probability. (extraordinary smaller)
So yes, it has a a huge sensitivity, but it is primarily a constructed sensitivity. All the Drake equation really tells us is that we don’t know very much and it probably won’t be useful until we can get N above one for more of the parameters.
The difference is that before people looked at the Drake equation, and thought that even with the uncertainty, there was a very low probability of no aliens, and this corrects that assumption.