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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

by 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.
      - jvanderbot 2y ago
        You can zoom out arbitrarily far to increase the odds, sure. But for discussion purposes i limited to our galaxy's 10^10-ish hypothesized planets.
    - eep_social 2y ago
      Right but the unstated assumption that there is no other positive path isn’t any more well-supported than the converse. For example, observe the variety of life we have locally. I’m thinking particularly of the various life (or life-like but I digress) that exists in extremes like thermal vents or under-explored places like deep soil. So maybe it does eliminate 1/10 but maybe we forgot to add the other 1/10 for life that wants to live at 100C (or whatever) — I’m pushing back on your assuredness, not the math.
      - deleted 2y ago
        [deleted]

by 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.
    - jvanderbot 2y ago
      You can zoom out arbitrarily far to increase the odds, sure. But for discussion purposes i limited to our galaxy's 10^10-ish hypothesized planets.
  - eep_social 2y ago
    Right but the unstated assumption that there is no other positive path isn’t any more well-supported than the converse. For example, observe the variety of life we have locally. I’m thinking particularly of the various life (or life-like but I digress) that exists in extremes like thermal vents or under-explored places like deep soil. So maybe it does eliminate 1/10 but maybe we forgot to add the other 1/10 for life that wants to live at 100C (or whatever) — I’m pushing back on your assuredness, not the math.
    - deleted 2y ago
      [deleted]