4 ms·

The steps don't have to be that hard for us to be unique. There are 10^22 to 10^24 stars in the Universe (a big range of uncertainty there but it doesn't matte

The steps don't have to be that hard for us to be unique. There are 10^22 to 10^24 stars in the Universe (a big range of uncertainty there but it doesn't matter for this point). That sounds like a lot but anyone with knowledge of combinatronics would immediately say holy shit that's a small number. Cryptography buffs are probably looking at that going "that can't be right, it's a tiny number", you divide it by 10 repeatedly, 24 times in fact and you're down to nothing. 24 not-at-all 'hard' steps and we're probably alone. You've probably heard "there's soooo many stars in the universe there has to be other life out there". There really isn't that many in terms of probability.

A_D_E_P_T 2y ago
This is too facile. The Copernican principle assumes that we are not in a spatially or temporally privileged position, and there are no obvious hard steps -- to say nothing of 24. It's frankly bizarre to go from there to "we are unique among 10^22 stars."
- AnotherGoodName 2y ago
  Having thoughts around how many stars are in the observable universe is a very reasonable starting point. Even without a privileged position the observable universe is still well defined in an expanding universe - at some boundary other stars are moving away too fast to be observed. So we can absolutely state this.
- DennisP 2y ago
  In this case the Copernican principle is at odds with the anthropic principle. If there were only one place in the universe with intelligent life, then necessarily that's where we would be. GP may be thinking of this paper, which uses a reasonable probability distribution for each parameter in the Drake equation, and finds a decent chance that there is no other technological civilization in the observable universe: https://arxiv.org/abs/1806.02404 https://arxiv.org/abs/1806.02404
  - jovial_cavalier 2y ago
    Invocations of the anthropic principle come with more baggage than may be realized. And I suppose, by extension, the Copernican principle too. https://www.scottaaronson.com/democritus/lec17.html https://www.scottaaronson.com/democritus/lec17.html
    - DennisP 2y ago
      Some people take it way too far, but I think my invocation was just trivially true. We can't come to any conclusion about the prevalence of life elsewhere in the universe, just based on the fact that we exist.
bluGill 2y ago
The speed of light is also a factor: most of those stars are so far away that they cannot detect our sun because to them it hasn't even lit up yet. (Our sun is about 4.6 billion years old, the universe is about 93 billion light years across). Stars like our sun are expected to last 10-12 billion years, so most stars that we think can support life in you 10^24 number have already died and we don't know it!. (stars need not be like our sun to support life, but I have to go with something to give numbers)
- qingcharles 2y ago
  And then you add in all the galaxies that are so far away our light will never reach them...
RAM-bunctious 2y ago
Not that I'd call myself a buff, but I don't think my knowledge of larger numbers makes 10^24 a small number in any absolute sense. Cryptographic keyspaces are deliberately designed to be unfathomly large, whereas the number of stars in the universe is simply an observational fact. The number of stars really is huge in a human sense, as much as that's worth anything. There are more stars than there are grains of sand, etc. The fact that we exist to discuss these odds means that whatever the probability distribution, at least one instance of life has occurred. Not only that, but life arose and eventually led to intelligence at our level - something that appears to be rare even on our own planet, but achieved relatively quickly all things concerned (only a few hundred million years). While the anthropic principle guarantees that we observe intelligence as we're defining it (since we include ourselves), I agree that doesn’t mean intelligence is inevitable or common. A more likely modelling in my opinion is that worlds of microbial life are abundant, worlds with complex multicellular life is rarer, and intelligent civilizations are rarer still. Given the distribution of intelligence levels on Earth, it seems unlikely that we simply passed every constraint while no other planet gets close. Also, if we observed a planet with humans as they were 100,000 years ago, would we even consider them intelligent life? Probably just as intelligent as modern-day humans if raised the same, but literally nowhere near our technological level. When scientists evaluate whether soil can support certaing thing, they don’t treat each factor (like pH, moisture, nutrients, microbial conditions) as independent hurdles that must be overcome one by one. Instead, they see that multiple factors interact in complex ways. A deficiency in one area (e.g., nutrient content) can be mitigated by another factor (e.g., microbial activity enhancing nutrient cycling). If you extend this to conditions in which life might it arise, it suggests to me that planetary habitability may be more like a network of contributing conditions rather than a checklist -- actually much more difficult to caclulate? Also, mostly as an aside, we also have the advantage of knowing that life and then intelligence arose relatively quickly once conditions stabilized - only a few hundred million years. n=1 but I think this is a promising indication on where any variables might lie.
d0odk 2y ago
Isn't that just the observable universe?
- AnotherGoodName 2y ago
  Yes although that's all we observe from the point of view of the fermi paradox so is very relevant.
  - d0odk 2y ago
    Ah, that makes sense. Given your original comment, I was considering unevenly distributed life across an infinite universe. But you're right of course, that is irrelevant to the fermi paradox.

A_D_E_P_T 2y ago

This is too facile. The Copernican principle assumes that we are not in a spatially or temporally privileged position, and there are no obvious hard steps -- to say nothing of 24. It's frankly bizarre to go from there to "we are unique among 10^22 stars."

AnotherGoodName 2y ago
Having thoughts around how many stars are in the observable universe is a very reasonable starting point. Even without a privileged position the observable universe is still well defined in an expanding universe - at some boundary other stars are moving away too fast to be observed. So we can absolutely state this.
DennisP 2y ago
In this case the Copernican principle is at odds with the anthropic principle. If there were only one place in the universe with intelligent life, then necessarily that's where we would be. GP may be thinking of this paper, which uses a reasonable probability distribution for each parameter in the Drake equation, and finds a decent chance that there is no other technological civilization in the observable universe: https://arxiv.org/abs/1806.02404 https://arxiv.org/abs/1806.02404
- jovial_cavalier 2y ago
  Invocations of the anthropic principle come with more baggage than may be realized. And I suppose, by extension, the Copernican principle too. https://www.scottaaronson.com/democritus/lec17.html https://www.scottaaronson.com/democritus/lec17.html
  - DennisP 2y ago
    Some people take it way too far, but I think my invocation was just trivially true. We can't come to any conclusion about the prevalence of life elsewhere in the universe, just based on the fact that we exist.

bluGill 2y ago

The speed of light is also a factor: most of those stars are so far away that they cannot detect our sun because to them it hasn't even lit up yet. (Our sun is about 4.6 billion years old, the universe is about 93 billion light years across). Stars like our sun are expected to last 10-12 billion years, so most stars that we think can support life in you 10^24 number have already died and we don't know it!. (stars need not be like our sun to support life, but I have to go with something to give numbers)

qingcharles 2y ago
And then you add in all the galaxies that are so far away our light will never reach them...

RAM-bunctious 2y ago

Not that I'd call myself a buff, but I don't think my knowledge of larger numbers makes 10^24 a small number in any absolute sense. Cryptographic keyspaces are deliberately designed to be unfathomly large, whereas the number of stars in the universe is simply an observational fact. The number of stars really is huge in a human sense, as much as that's worth anything. There are more stars than there are grains of sand, etc. The fact that we exist to discuss these odds means that whatever the probability distribution, at least one instance of life has occurred. Not only that, but life arose and eventually led to intelligence at our level - something that appears to be rare even on our own planet, but achieved relatively quickly all things concerned (only a few hundred million years). While the anthropic principle guarantees that we observe intelligence as we're defining it (since we include ourselves), I agree that doesn’t mean intelligence is inevitable or common. A more likely modelling in my opinion is that worlds of microbial life are abundant, worlds with complex multicellular life is rarer, and intelligent civilizations are rarer still. Given the distribution of intelligence levels on Earth, it seems unlikely that we simply passed every constraint while no other planet gets close. Also, if we observed a planet with humans as they were 100,000 years ago, would we even consider them intelligent life? Probably just as intelligent as modern-day humans if raised the same, but literally nowhere near our technological level. When scientists evaluate whether soil can support certaing thing, they don’t treat each factor (like pH, moisture, nutrients, microbial conditions) as independent hurdles that must be overcome one by one. Instead, they see that multiple factors interact in complex ways. A deficiency in one area (e.g., nutrient content) can be mitigated by another factor (e.g., microbial activity enhancing nutrient cycling). If you extend this to conditions in which life might it arise, it suggests to me that planetary habitability may be more like a network of contributing conditions rather than a checklist -- actually much more difficult to caclulate? Also, mostly as an aside, we also have the advantage of knowing that life and then intelligence arose relatively quickly once conditions stabilized - only a few hundred million years. n=1 but I think this is a promising indication on where any variables might lie.

d0odk 2y ago

Isn't that just the observable universe?

AnotherGoodName 2y ago
Yes although that's all we observe from the point of view of the fermi paradox so is very relevant.
- d0odk 2y ago
  Ah, that makes sense. Given your original comment, I was considering unevenly distributed life across an infinite universe. But you're right of course, that is irrelevant to the fermi paradox.