11 ms·

True, but Dyson spheres should be easily visible in the infrared, and I know searching for them is set as an undergrad project by at least one IR astronomy prof

True, but Dyson spheres should be easily visible in the infrared, and I know searching for them is set as an undergrad project by at least one IR astronomy professor. So, I’d expect them to be spotted by now if they are widespread.

CryptoPunk 7y ago
Apparently Dyson spheres can be undetectable with IR telescopes: https://www.tillett.info/2016/08/03/carnot-efficient-dyson-spheres-are-undetectable-by-infrared-surveys/ https://www.tillett.info/2016/08/03/carnot-efficient-dyson-s...
ceejayoz 7y ago
It seems silly for us to make a bunch of rigid conclusions about an unimaginably high technology solar-system scale megastructure.
- ben_w 7y ago
  We could make one with known tech, it would only take a few thousand years thanks to exponential population growth and humans being universal constructors. We’d expect to see Dyson swarms’ heat signatures because of the laws of thermodynamics. If super-advanced aliens can avoid or circumvent thermodynamics, all bets are off.
  - ceejayoz 7y ago
    The laws of thermodynamics don't forbid radiating heat in a directed manner, right?
    - ben_w 7y ago
      I think you’re only able to do that if you’re not in thermal equilibrium. I’m not a trained physicist, so I’m not 100% certain about this, however the phrase “there is no stealth in space” seems to come up a lot in the stuff I read, and that specifically excludes directing heat away in specific directions.
      - ceejayoz 7y ago
        I'd think you could do something like have a deep, V-shaped hole with radiators at the bottom, and really good insulation / conductors throughout the sphere to funnel heat into that radiator. Anything radiating in the wrong direction would just get picked back up and re-directed through the system again. Point that V into deep intergalactic space and buy yourself a few hundred million years.
- cogman10 7y ago
  I don't think it is crazy silly to expect that, before a dyson sphere is built, dyson rings would be built. I think that's where the distinct IR signature is coming into play.
  - jerf 7y ago
    It's the whole shebang. Basic thermodynamics. Suppose you did perfectly insulate... anything. Any system that is also generating and consuming power. That means no energy is escaping. That means all energy being produced is turning into heat on the inside. That means the inside is going to become... unpleasant. In not necessarily all that large an amount of time on human time scales, let alone cosmological ones. A Dyson Sphere has to radiate. As ben_w said and I fully agree with, if you're going to hypothesize a level of technology that can somehow get around that, that's fine and all, but if you're going to invoke magic, you really haven't got any justification for stopping at such a particular place. They could be aliens that have figured out how to shunt energy into the 5th Dimension instead of radiating it out into our universe... but they might also just be elves casting magic spells. Intuitively, it may seem like there's a lot of difference between those two things, but... there really isn't so much.
    - snovv_crash 7y ago
      It isn't unimaginable that they can control the direction of the radiation. It could be directed away from the galactic plane, for example.
    - koheripbal 7y ago
      Perhaps the radiation can be directed. Who's to say it would be omnidirectional?

CryptoPunk 7y ago

Apparently Dyson spheres can be undetectable with IR telescopes: https://www.tillett.info/2016/08/03/carnot-efficient-dyson-spheres-are-undetectable-by-infrared-surveys/ https://www.tillett.info/2016/08/03/carnot-efficient-dyson-s...

ceejayoz 7y ago

It seems silly for us to make a bunch of rigid conclusions about an unimaginably high technology solar-system scale megastructure.

ben_w 7y ago
We could make one with known tech, it would only take a few thousand years thanks to exponential population growth and humans being universal constructors. We’d expect to see Dyson swarms’ heat signatures because of the laws of thermodynamics. If super-advanced aliens can avoid or circumvent thermodynamics, all bets are off.
- ceejayoz 7y ago
  The laws of thermodynamics don't forbid radiating heat in a directed manner, right?
  - ben_w 7y ago
    I think you’re only able to do that if you’re not in thermal equilibrium. I’m not a trained physicist, so I’m not 100% certain about this, however the phrase “there is no stealth in space” seems to come up a lot in the stuff I read, and that specifically excludes directing heat away in specific directions.
    - ceejayoz 7y ago
      I'd think you could do something like have a deep, V-shaped hole with radiators at the bottom, and really good insulation / conductors throughout the sphere to funnel heat into that radiator. Anything radiating in the wrong direction would just get picked back up and re-directed through the system again. Point that V into deep intergalactic space and buy yourself a few hundred million years.
cogman10 7y ago
I don't think it is crazy silly to expect that, before a dyson sphere is built, dyson rings would be built. I think that's where the distinct IR signature is coming into play.
- jerf 7y ago
  It's the whole shebang. Basic thermodynamics. Suppose you did perfectly insulate... anything. Any system that is also generating and consuming power. That means no energy is escaping. That means all energy being produced is turning into heat on the inside. That means the inside is going to become... unpleasant. In not necessarily all that large an amount of time on human time scales, let alone cosmological ones. A Dyson Sphere has to radiate. As ben_w said and I fully agree with, if you're going to hypothesize a level of technology that can somehow get around that, that's fine and all, but if you're going to invoke magic, you really haven't got any justification for stopping at such a particular place. They could be aliens that have figured out how to shunt energy into the 5th Dimension instead of radiating it out into our universe... but they might also just be elves casting magic spells. Intuitively, it may seem like there's a lot of difference between those two things, but... there really isn't so much.
  - snovv_crash 7y ago
    It isn't unimaginable that they can control the direction of the radiation. It could be directed away from the galactic plane, for example.
  - koheripbal 7y ago
    Perhaps the radiation can be directed. Who's to say it would be omnidirectional?