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Yeah but 25% of a few hundred billion (planets in the milky way) is still a fair lot of opportunities. “Space is big. You just won't believe how vastly, hugely

Yeah but 25% of a few hundred billion (planets in the milky way) is still a fair lot of opportunities. “Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is.”

jvanderbot 2y ago
Well I suppose it's fair to say that only 1/8 planets has plate techtonics, and AFAIK, none of the dozens of moons either.
- MPSimmons 2y ago
  I thought Titan did (though in that case, I think it's more ice quakes)
  - mnky9800n 2y ago
    But earthquakes and plate tectonics are not the same thing
- eep_social 2y ago
  I think the point is that we know the numerator today is one, and no matter how much you cut down the denominator, increasing the numerator to two would be a huge deal. Conversely, given that we think the denominator approaches a small infinity, it seems implausible that the numerator is actually one.
  - jvanderbot 2y ago
    Well that's not my point. Right now the denominator is about 10 trillion. A single 1/10 factor makes it 1 trillion. 10-ish more factors and we're down to a small number of planets before we even consider the emergence of life and likelihood of propagation. There are likely many more 1/10 factors: Habitable zone, diurnal cycles, billions of years of geological peace, sufficient water, a stable moon (maybe only one), a particular spectra of the star ... all those were "well they seem to happen to 1/10 or 1/100 planets" individually. They cut down the space quickly when combined.
  - irrational 2y ago
    But, the 2 may be on the other side of the universe, or even past the cosmological horizon. And since FTL speed travel is almost certainly impossible, it may very well always be 1 to the best of our knowledge.
    - eep_social 2y ago
      That’s what makes this discussion so fun ;)
- TomK32 2y ago
  Even 1 in a million (planets) would allow for 100 thousand solar systems in the 100 billion stars strong galaxy to have at least one tectonic active planet; not counting moons.
  - jvanderbot 2y ago
    As stated in another thread, it's yet another 80% reduction in the number of habitable worlds. On top of all the factors, the exponential decay is pretty steep. That's just the nature of the drake equation. It's very much a geometric series and if all factors have to line up with 1/10 odds, you only need 10-ish "vital things" to cancel basically all chance of life except earth. And here we have a hypothesis which might be about 1/10 odds and might be vital. 9 left. Water? Diurnal duration? Spectrum of star? A billion years of peace? A moon? A magnetic field? There's potentially lots of factors.
    - eep_social 2y ago
      Seems to me like “basically” is doing a lot of work, that leaves behind what.. a few billion planets?
      - jvanderbot 2y ago
        "basically" is doing only what I suggested: a geometric series. Here's exactly what work it's doing: Pretend there's 10s of trillions of planets. That's 10-13 zeros depending on whose estimate you trust most. 1/10 factor cancels one zero. at most 13 factors accumulated means you have 1 habitable planet out of all those planets. We have just hypothesized a 1/10 factor in this thread - that leaves 12 more - and I've lised 6 more off the top of my head. It's just a fermi question - ballpark estimates like that are a way of thinking of the relative scale. A 1/10 chance seems like it leaves a lot of planets left (as you say - 100s of billions), but there are already many 1/10 factors floating around.
        delta_p_delta_x 2y ago
        The Milky Way alone has about 2.5 × 10^11 stars. The Andromeda Galaxy has around 10^12. Let's take 0.5 × 10^12 stars on average per galaxy. There are about 2.5 × 10^11 galaxies in the observable universe. This gives us around 10^23 stars in the universe to fiddle with. Assume every star has an average of 2 planets; some have more, some have none. This is a pretty large number to trim down. I'd argue the Drake equation is excessively conservative. Note that when microbial life first emerged on Earth 4.1 billion years ago, the Earth's atmosphere was rather reducing, and the Sun was around 30% less luminous than it is today. There was free water, but no free oxygen, and an extremely high-pressure CO2 atmosphere. The universe is arguably extremely young; the longest-lasting stars will only burn out around 10^13 years from now, and the universe is barely 10^10 years old. It's fair to say that many sun-like stars haven't even formed yet.

Yeah but 25% of a few hundred billion (planets in the milky way) is still a fair lot of opportunities. “Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is.”

jvanderbot 2y ago

Well I suppose it's fair to say that only 1/8 planets has plate techtonics, and AFAIK, none of the dozens of moons either.

MPSimmons 2y ago
I thought Titan did (though in that case, I think it's more ice quakes)
- mnky9800n 2y ago
  But earthquakes and plate tectonics are not the same thing
eep_social 2y ago
I think the point is that we know the numerator today is one, and no matter how much you cut down the denominator, increasing the numerator to two would be a huge deal. Conversely, given that we think the denominator approaches a small infinity, it seems implausible that the numerator is actually one.
- jvanderbot 2y ago
  Well that's not my point. Right now the denominator is about 10 trillion. A single 1/10 factor makes it 1 trillion. 10-ish more factors and we're down to a small number of planets before we even consider the emergence of life and likelihood of propagation. There are likely many more 1/10 factors: Habitable zone, diurnal cycles, billions of years of geological peace, sufficient water, a stable moon (maybe only one), a particular spectra of the star ... all those were "well they seem to happen to 1/10 or 1/100 planets" individually. They cut down the space quickly when combined.
- irrational 2y ago
  But, the 2 may be on the other side of the universe, or even past the cosmological horizon. And since FTL speed travel is almost certainly impossible, it may very well always be 1 to the best of our knowledge.
  - eep_social 2y ago
    That’s what makes this discussion so fun ;)
TomK32 2y ago
Even 1 in a million (planets) would allow for 100 thousand solar systems in the 100 billion stars strong galaxy to have at least one tectonic active planet; not counting moons.
- jvanderbot 2y ago
  As stated in another thread, it's yet another 80% reduction in the number of habitable worlds. On top of all the factors, the exponential decay is pretty steep. That's just the nature of the drake equation. It's very much a geometric series and if all factors have to line up with 1/10 odds, you only need 10-ish "vital things" to cancel basically all chance of life except earth. And here we have a hypothesis which might be about 1/10 odds and might be vital. 9 left. Water? Diurnal duration? Spectrum of star? A billion years of peace? A moon? A magnetic field? There's potentially lots of factors.
  - eep_social 2y ago
    Seems to me like “basically” is doing a lot of work, that leaves behind what.. a few billion planets?
    - jvanderbot 2y ago
      "basically" is doing only what I suggested: a geometric series. Here's exactly what work it's doing: Pretend there's 10s of trillions of planets. That's 10-13 zeros depending on whose estimate you trust most. 1/10 factor cancels one zero. at most 13 factors accumulated means you have 1 habitable planet out of all those planets. We have just hypothesized a 1/10 factor in this thread - that leaves 12 more - and I've lised 6 more off the top of my head. It's just a fermi question - ballpark estimates like that are a way of thinking of the relative scale. A 1/10 chance seems like it leaves a lot of planets left (as you say - 100s of billions), but there are already many 1/10 factors floating around.
      - delta_p_delta_x 2y ago
        The Milky Way alone has about 2.5 × 10^11 stars. The Andromeda Galaxy has around 10^12. Let's take 0.5 × 10^12 stars on average per galaxy. There are about 2.5 × 10^11 galaxies in the observable universe. This gives us around 10^23 stars in the universe to fiddle with. Assume every star has an average of 2 planets; some have more, some have none. This is a pretty large number to trim down. I'd argue the Drake equation is excessively conservative. Note that when microbial life first emerged on Earth 4.1 billion years ago, the Earth's atmosphere was rather reducing, and the Sun was around 30% less luminous than it is today. There was free water, but no free oxygen, and an extremely high-pressure CO2 atmosphere. The universe is arguably extremely young; the longest-lasting stars will only burn out around 10^13 years from now, and the universe is barely 10^10 years old. It's fair to say that many sun-like stars haven't even formed yet.