Even a Dyson sphere, which is technically unlikely anyway, would be possible to spot. You would look for something very bright in the infrared spectrum with almost no light in the visible spectrum. It would also be larger than a normal star of the same energy, but that would be hard to tell given all the other issues.
A partial swarm is easier because it will have variability towards more infrared and then back to a more normal spectrum.
And, of course, all this is speculation until we find a candidate and determine it doesn’t have a natural source for that behavior.
Why would there necessarily be strong infrared emissions? Since a Dyson Sphere is meant to harvest all energy produced by a star, any leakage would be unnecessary inefficiency, wouldn’t it?
Thermodynamics says that energy can’t be destroyed (mass-energy, but generally that won’t matter). So after the work of running your stellar civilization is done, you will radiate out waste heat. There is no real way around this without breaking thermodynamics or having a handy black hole to dump all your waste heat into. Therefore, the energy of the star will still be released, but it will be released as infrared.
If you’re using the Dyson sphere purely as a power plant and e.g. charge batteries, the thermal radiation will be distributed over the whole area covered by the civilization.
A solar panel, or any other power generator we use, doesn’t radiate away all the generated energy either. It’s radiated from the point of use.
So you heat habitats, which radiate heat. And run computers, which radiate heat. And move objects around, which radiates heat (among other things). And if you merely absorb energy from your star…it radiates as heat. This is the whole idea of entropy. Unless your lasers are particularly efficient and you use them to beam the energy elsewhere, your Dyson swarm is going to radiate heat equivalent to the energy your star puts out.
You’re ignoring my example - what if you charge up batteries at the Dyson sphere, and use the energy anywhere else? There’s no physical reason the energy must be used around the Dyson sphere.
So all you need is a perfect charging system. We don’t have those, and physics doesn’t allow for them. This would be no different than the laser example I gave, and this only makes sense after you have a second Dyson swarm.
Why perfect? As long as the efficiency is high enough, you wouldn’t see the sphere itself as very bright, it would be quite dim. Do we know any hard, physical limitations for this, like we do for speed?
But you would still be radiating heat from that star system unless you’re proposing wireless energy transfer over Interstellar distances. So the entire system would still give off an unusually high infrared signature.
I’m not proposing that - I literally wrote my idea in the comment you replied to: a potential alien civilization could charge up batteries at their Dyson sphere, and use the energy anywhere else in the galaxy. You know, the way EVs work.
Sure, you won’t reach 100%. But say you reach 99.9% - the Dyson sphere should radiate infrared at 0.1% of a normal star, right? It wouldn’t necessarily be bright.
Even if that level of efficiency were possible, 0.01% of a star’s output is still a substantial amount of heat. You would still have to radiate it away otherwise it would melt your mega structure, and you would have to radiate it out equally in all directions otherwise you’d knock it off its orbit with the thrust generated from the radiating of the heat on one side.
Dyson swarms are more likely. We even have a tiny one with our satellites using solar power in a heliocentric orbit. (Dyson spheres are basically impossible.) But we could theoretically detect either in infrared since if it doesn’t give off waste heat, it’d all heat up and melt.
That being said, I’m personally of the opinion this is a waste of time. Not to get all Fermi Paradox but it’s pretty sci fi brained to think any other species out there is as dumb as we are. Space sucks. You die super fast there. Everything had to align just right for Earth to make a bunch of dumb fuck apes willing to strap themselves onto rockets, have a planet small enough that the rocket could even overcome gravity to enter orbit using chemical rockets, and a World War and Cold War to accelerate things.
Time will always be the great filter. Even if we did spot a Dyson swarm, we have no feasible way to contact anything on a practice timescale. Any speck of civilization we detect will be hundreds of thousands of years out of date at best, billions at worst. Life in the universe, imo, is basically guaranteed. If it happened once, it can happen again. Meaningful contact between separately evolved concurrent sapient species? Not likely.
Everything had to align just right for Earth to make a bunch of dumb fuck apes willing to strap themselves onto rockets, have a planet small enough that the rocket could even overcome gravity to enter orbit using chemical rockets, and a World War and Cold War to accelerate things.
Given the estimated number of planets in this galaxy alone, it’s particularly guaranteed that very similar events have occurred on multiple worlds. Unless you’re proposing that all theoretical alien races are Vulcan level logical then tensions and interstate conflicts will always exist that will advance technology. This is practically an inevitability unless the race question is a hive mind species.
Not to mention the problem of what life is even supposed to do beyond a certain point of development. The depressing fact is that there is a finite amount of knowledge to be gained, a finite amount of resources to harvest, a finite diversity of life to contend or thrive alongside with. Once a pocket of life in this massive universe begins to run out of things to do and stagnates, then what? What is there to think about; to feel; to experience?
There’s little point in exploring space if one know how this universe works. One knows the rules, knows all the ways it can play out, and there’s no surprise waiting on the other end of any venture one can imagine embarking on.
That’s my theory. The Great Filter is just depressive boredom. We don’t see other life because by the time a civilisation is able and ready to spend thousands of years travelling through deep space, they’ll have already lost any motivation they might have had to do so.
I suspect that there’s at best a very short window wherein a species is both knowledgeable enough to dream of space exploration and technologically capable of sending any significant amount of artificial constructions out there.
Not to mention that anything an alien species might send into interstellar space is unimaginably unlikely to be recorded exactly at precisely the moment they pass another lump of matter - especially if the window is as short as I fear.
If it was actually completely enclosing a star that would be impressive. It would also be a bit pointless, since It would result in your spear heating up to stupid temperatures, Which would cause it to glow in the infrared, so you would detect it by that infrared.
Okay, so the title is a bit off. They’re hunting for partial Dyson spheres using infrared and optical.
I was confused on how they would detect something completely blocking a sun from millions of light-years away.
Even a Dyson sphere, which is technically unlikely anyway, would be possible to spot. You would look for something very bright in the infrared spectrum with almost no light in the visible spectrum. It would also be larger than a normal star of the same energy, but that would be hard to tell given all the other issues.
A partial swarm is easier because it will have variability towards more infrared and then back to a more normal spectrum.
And, of course, all this is speculation until we find a candidate and determine it doesn’t have a natural source for that behavior.
Why would there necessarily be strong infrared emissions? Since a Dyson Sphere is meant to harvest all energy produced by a star, any leakage would be unnecessary inefficiency, wouldn’t it?
Thermodynamics says that energy can’t be destroyed (mass-energy, but generally that won’t matter). So after the work of running your stellar civilization is done, you will radiate out waste heat. There is no real way around this without breaking thermodynamics or having a handy black hole to dump all your waste heat into. Therefore, the energy of the star will still be released, but it will be released as infrared.
If you’re using the Dyson sphere purely as a power plant and e.g. charge batteries, the thermal radiation will be distributed over the whole area covered by the civilization.
A solar panel, or any other power generator we use, doesn’t radiate away all the generated energy either. It’s radiated from the point of use.
So you heat habitats, which radiate heat. And run computers, which radiate heat. And move objects around, which radiates heat (among other things). And if you merely absorb energy from your star…it radiates as heat. This is the whole idea of entropy. Unless your lasers are particularly efficient and you use them to beam the energy elsewhere, your Dyson swarm is going to radiate heat equivalent to the energy your star puts out.
You’re ignoring my example - what if you charge up batteries at the Dyson sphere, and use the energy anywhere else? There’s no physical reason the energy must be used around the Dyson sphere.
So all you need is a perfect charging system. We don’t have those, and physics doesn’t allow for them. This would be no different than the laser example I gave, and this only makes sense after you have a second Dyson swarm.
Why perfect? As long as the efficiency is high enough, you wouldn’t see the sphere itself as very bright, it would be quite dim. Do we know any hard, physical limitations for this, like we do for speed?
But you would still be radiating heat from that star system unless you’re proposing wireless energy transfer over Interstellar distances. So the entire system would still give off an unusually high infrared signature.
I’m not proposing that - I literally wrote my idea in the comment you replied to: a potential alien civilization could charge up batteries at their Dyson sphere, and use the energy anywhere else in the galaxy. You know, the way EVs work.
Because all that energy contains heat as well, and you’ll need to balance the heat from your star along with the energy absorbed.
You’re never going to get to 100% efficient conversion, so you’ll have to radiate away the heat so your sphere doesn’t melt or something.
Sure, you won’t reach 100%. But say you reach 99.9% - the Dyson sphere should radiate infrared at 0.1% of a normal star, right? It wouldn’t necessarily be bright.
Not all heat can be converted to work by the second law of thermodynamics. Now the question is, how hot can the star be for it to sustain life? Can most of its light be UV with very little visible? https://courses.lumenlearning.com/suny-physics/chapter/15-4-carnots-perfect-heat-engine-the-second-law-of-thermodynamics-restated/
They must be mining a lot of bitcoin to need 99.9% of a star’s energy.
Or else to power one of those Kurtzgestat space lasers that will melt us anyway.
Maybe they are just fabricating matter. That takes a surprising amount of energy!
Even if that level of efficiency were possible, 0.01% of a star’s output is still a substantial amount of heat. You would still have to radiate it away otherwise it would melt your mega structure, and you would have to radiate it out equally in all directions otherwise you’d knock it off its orbit with the thrust generated from the radiating of the heat on one side.
Yeah, it’s interesting to think about IR powered thrust.
I wonder if moving a star by cooling one side could ever happen? Like in a some weird future tech way obviously.
Dyson swarms are more likely. We even have a tiny one with our satellites using solar power in a heliocentric orbit. (Dyson spheres are basically impossible.) But we could theoretically detect either in infrared since if it doesn’t give off waste heat, it’d all heat up and melt.
That being said, I’m personally of the opinion this is a waste of time. Not to get all Fermi Paradox but it’s pretty sci fi brained to think any other species out there is as dumb as we are. Space sucks. You die super fast there. Everything had to align just right for Earth to make a bunch of dumb fuck apes willing to strap themselves onto rockets, have a planet small enough that the rocket could even overcome gravity to enter orbit using chemical rockets, and a World War and Cold War to accelerate things.
Time will always be the great filter. Even if we did spot a Dyson swarm, we have no feasible way to contact anything on a practice timescale. Any speck of civilization we detect will be hundreds of thousands of years out of date at best, billions at worst. Life in the universe, imo, is basically guaranteed. If it happened once, it can happen again. Meaningful contact between separately evolved concurrent sapient species? Not likely.
Given the estimated number of planets in this galaxy alone, it’s particularly guaranteed that very similar events have occurred on multiple worlds. Unless you’re proposing that all theoretical alien races are Vulcan level logical then tensions and interstate conflicts will always exist that will advance technology. This is practically an inevitability unless the race question is a hive mind species.
I think my Fermi Paradox explanation is that space is really fucking big and hostile and protecting the planet you evolved on is the only real option.
Not to mention the problem of what life is even supposed to do beyond a certain point of development. The depressing fact is that there is a finite amount of knowledge to be gained, a finite amount of resources to harvest, a finite diversity of life to contend or thrive alongside with. Once a pocket of life in this massive universe begins to run out of things to do and stagnates, then what? What is there to think about; to feel; to experience?
There’s little point in exploring space if one know how this universe works. One knows the rules, knows all the ways it can play out, and there’s no surprise waiting on the other end of any venture one can imagine embarking on.
That’s my theory. The Great Filter is just depressive boredom. We don’t see other life because by the time a civilisation is able and ready to spend thousands of years travelling through deep space, they’ll have already lost any motivation they might have had to do so.
I suspect that there’s at best a very short window wherein a species is both knowledgeable enough to dream of space exploration and technologically capable of sending any significant amount of artificial constructions out there.
Not to mention that anything an alien species might send into interstellar space is unimaginably unlikely to be recorded exactly at precisely the moment they pass another lump of matter - especially if the window is as short as I fear.
If it was actually completely enclosing a star that would be impressive. It would also be a bit pointless, since It would result in your spear heating up to stupid temperatures, Which would cause it to glow in the infrared, so you would detect it by that infrared.
Isn’t the idea that the sphere would have a circumference the size of earths orbit? Not sure it would heat up all that much to be noticeable.