5 ms·

I understand that in 500m years luminosity will increase by 5%. By then we should be able to survive that modest increase. Where did you get 500m years?

mystified5016 1y ago
As you said, luminosity increases. It isn't a matter of survival, it's a physics problem. If a planet absorbs more energy from its star than it's capable of radiating away, it will rise in temperature forever until and unless energy output increases above energy input. And when you consider that by this point energy input is on a permanent increase, there's really not much you can do apart from moving the whole damn planet out of the way. It's kind of pointless to speculate what kind of technology we'll have in 500m years (or indeed if there is a 'we' left in the system). The time scale is so enormous that there's simply no way to predict anything at all involving humans or human-derivatives. The planet (without literally unimaginable intervention) will heat up and become uninhabitable sometime around 500m years from now.
- datadrivenangel 1y ago
  I suspect with the right mix of aerosol injection and additional megaengineering of radiators pointing to deep space we could make that work
- thebruce87m 1y ago
  > there's really not much you can do apart from moving the whole damn planet out of the way. You can put something in between, a giant sun shade
  - WillAdams 1y ago
    Or a giant solar array?
  - thfuran 1y ago
    Can you without making a ringworld?
    - thebruce87m 1y ago
      I guess you’re thinking of something that orbits earth? If you build something that orbits the sun at the same rate as us then it could just be flat and circular. Maybe someone smarter than me can calculate the optimal parameters to get the smallest shade that orbits the sun. If we are looking to only block out a percentage of the sun then it doesn’t even need to be fully opaque, maybe a giant dream catcher would be fine.
      - hinkley 1y ago
        https://en.wikipedia.org/wiki/Lagrange_point https://en.wikipedia.org/wiki/Lagrange_point And already a known option for our current global warming situation.
      - thfuran 1y ago
        >orbits the sun at the same rate as us That means you're heavily restricted in where you can put it. It has to be either right next to earth, in which case it's hard to keep away from Earth, or at L1, which is not stable. There's no other place you can put something where it will stay directly between us and the sun.
        thebruce87m 1y ago
        Why restricted? Are we assuming it does not produce thrust here? Because it could.
        thfuran 1y ago
        It's wildly impractical to try to keep something far from a stable orbit with active thrust long-term. I mean, why don't we all have flying houses? It'd be cool.
    - rendall 1y ago
  - mattigames 1y ago
    Chunks of other planets, we have always been pretty good at creating explosives previous generations couldn't even fathom so such destructive disposition may get to be a positive thing for once.
  - bravesoul2 1y ago
    Can artificial clouds help? Geo hacking might be cheaper than building billions of acres of shade.
    - looofooo0 1y ago
      We just build an L1 Solar park for micro g manufacturing of space mined materials.
- Bootvis 1y ago
  The interest in speculating, to me at least, is the impact of intelligent life still existing. It puts an upper bound on the life span on single planet species.
  - MangoToupe 1y ago
    ...it also pushes the lower bound lower :( really it just means we can extrapolate less from the historical record than had we not evolved, although I suppose that's a rather silly statement to make given that it was "non-intelligent" life that produced us in the only sample we have. Now I'm actually morbidly curious: do you think humans could even come close to sterilizing this planet if we wanted to? I mean maybe we could burn away the atmosphere if we set off enough nukes (probably more than humanity's ready-to-use-stockpile, I think?), but the biomass that's inside the ocean (...would that even remain without an atmosphere or would it boil off? regardless...) and crust is simply massive. I strongly suspect that life would keep on going.
- Retric 1y ago
  > If a planet absorbs more energy from its star than it's capable of radiating away, it will rise in temperature forever until and unless energy output increases above energy input. That’s a really misleading way to describe what going on. The amount of energy radiated into space is a function of temperature, so increasing incoming radiation also increases outgoing radiation. 5% increase in luminosity is roughly 3.5C increase in earths average surface temperatures ignoring other effects. However, you get a feedback loop as water vapor is a greenhouse gas which makes things hard to model. Here’s a study suggesting the tipping point is on 1 billion years https://www.sciencedaily.com/releases/2013/12/131216142310.htm https://www.sciencedaily.com/releases/2013/12/131216142310.h... but it’s not suggesting the oceans literally boil but rather a transition point where there’s a lot more water in the atmosphere.

mystified5016 1y ago

As you said, luminosity increases. It isn't a matter of survival, it's a physics problem. If a planet absorbs more energy from its star than it's capable of radiating away, it will rise in temperature forever until and unless energy output increases above energy input. And when you consider that by this point energy input is on a permanent increase, there's really not much you can do apart from moving the whole damn planet out of the way. It's kind of pointless to speculate what kind of technology we'll have in 500m years (or indeed if there is a 'we' left in the system). The time scale is so enormous that there's simply no way to predict anything at all involving humans or human-derivatives. The planet (without literally unimaginable intervention) will heat up and become uninhabitable sometime around 500m years from now.

datadrivenangel 1y ago
I suspect with the right mix of aerosol injection and additional megaengineering of radiators pointing to deep space we could make that work
thebruce87m 1y ago
> there's really not much you can do apart from moving the whole damn planet out of the way. You can put something in between, a giant sun shade
- WillAdams 1y ago
  Or a giant solar array?
- thfuran 1y ago
  Can you without making a ringworld?
  - thebruce87m 1y ago
    I guess you’re thinking of something that orbits earth? If you build something that orbits the sun at the same rate as us then it could just be flat and circular. Maybe someone smarter than me can calculate the optimal parameters to get the smallest shade that orbits the sun. If we are looking to only block out a percentage of the sun then it doesn’t even need to be fully opaque, maybe a giant dream catcher would be fine.
    - hinkley 1y ago
      https://en.wikipedia.org/wiki/Lagrange_point https://en.wikipedia.org/wiki/Lagrange_point And already a known option for our current global warming situation.
    - thfuran 1y ago
      >orbits the sun at the same rate as us That means you're heavily restricted in where you can put it. It has to be either right next to earth, in which case it's hard to keep away from Earth, or at L1, which is not stable. There's no other place you can put something where it will stay directly between us and the sun.
      - thebruce87m 1y ago
        Why restricted? Are we assuming it does not produce thrust here? Because it could.
        thfuran 1y ago
        It's wildly impractical to try to keep something far from a stable orbit with active thrust long-term. I mean, why don't we all have flying houses? It'd be cool.
  - rendall 1y ago
- mattigames 1y ago
  Chunks of other planets, we have always been pretty good at creating explosives previous generations couldn't even fathom so such destructive disposition may get to be a positive thing for once.
- bravesoul2 1y ago
  Can artificial clouds help? Geo hacking might be cheaper than building billions of acres of shade.
  - looofooo0 1y ago
    We just build an L1 Solar park for micro g manufacturing of space mined materials.
Bootvis 1y ago
The interest in speculating, to me at least, is the impact of intelligent life still existing. It puts an upper bound on the life span on single planet species.
- MangoToupe 1y ago
  ...it also pushes the lower bound lower :( really it just means we can extrapolate less from the historical record than had we not evolved, although I suppose that's a rather silly statement to make given that it was "non-intelligent" life that produced us in the only sample we have. Now I'm actually morbidly curious: do you think humans could even come close to sterilizing this planet if we wanted to? I mean maybe we could burn away the atmosphere if we set off enough nukes (probably more than humanity's ready-to-use-stockpile, I think?), but the biomass that's inside the ocean (...would that even remain without an atmosphere or would it boil off? regardless...) and crust is simply massive. I strongly suspect that life would keep on going.
Retric 1y ago
> If a planet absorbs more energy from its star than it's capable of radiating away, it will rise in temperature forever until and unless energy output increases above energy input. That’s a really misleading way to describe what going on. The amount of energy radiated into space is a function of temperature, so increasing incoming radiation also increases outgoing radiation. 5% increase in luminosity is roughly 3.5C increase in earths average surface temperatures ignoring other effects. However, you get a feedback loop as water vapor is a greenhouse gas which makes things hard to model. Here’s a study suggesting the tipping point is on 1 billion years https://www.sciencedaily.com/releases/2013/12/131216142310.htm https://www.sciencedaily.com/releases/2013/12/131216142310.h... but it’s not suggesting the oceans literally boil but rather a transition point where there’s a lot more water in the atmosphere.