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Could stars blacked out by Dyson spheres or other technology that completely harnesses their energy be an explanation for dark matter? Or would this matter not

Could stars blacked out by Dyson spheres or other technology that completely harnesses their energy be an explanation for dark matter? Or would this matter not be so "dark" due to the heat signature?

awb 5y ago
I think most if not every galaxy has dark matter so if it’s Dyson spheres that would mean that nearly every galaxy was colonized with Dyson spheres in the same way (except ours because we don’t have evidence of a galaxy-wide civilization).
maxander 5y ago
Indeed, Dyson spheres would need to release some amount of waste heat, due to the laws of thermodynamics. If there were too many of them that heat would be visible (at least to infrared telescopes,) so we know that’s not the explanation for dark matter. Same with dust and other non-luminescent matter- it’s all way more visible than dark matter has to be, somehow.
- freemint 5y ago
  What prevents that waste head being as warm ad the peak in cosmic background background radiation
  - ncmncm 5y ago
    Literally every last thing in the whole universe that can radiate heat is at least as warm as the cosmic background radiation. You cannot shed any heat at all unless you are warmer than the background radiation, because you would be absorbing as much heat from it as you radiate. If you were colder, you would necessarily be absorbing more. Thermodynamics does not play around.
buryat 5y ago
what would prevent an intelligent civilization from covering all other stars in dyson spheres? and the dark matter is everywhere (almost, there're galaxies without it) which would mean that most of the universe has intelligent life but then why there's no other signals? something should've leaked/pointed at it
- ncmncm 5y ago
  What would prevent it? Good sense. To be able to do it is to know better than to bother.
ncmncm 5y ago
In a word, no. Any sort of Dyson-spherish thing would radiate in infrared, and not be dark at all. A long time ago somebody went looking for these infrared emitters, and found billions (and billions) of them in our galaxy alone. Turns out low-grade infrared-emitting stars and star-like things are more common than dirt. There is no way to tell them apart from a hypothetical Dyson thingy, even if there were any actual reason ever to build one of those. (Which, hint, there isn't.)
- MattPalmer1086 5y ago
  The introduction to the article says: "The observational signatures of such “Dyson spheres” include waste-heat from the absorbing sphere, obscured direct star light (resulting in both an apparently underluminous star and potential temporal variations in brightness) and the effects of feedback on the properties of the star from the surrounding sphere." So there are ways to distinguish probable Dyson spheres from the majority of these natural infrared sources.
  - ncmncm 5y ago
    That would depend on somebody, anybody seeing any reason to build so much as one of them. You might imagine a playful civilization building one next-system-over to fool planet-bound hicks who actually still believe they are a good idea. The hicks restructure their whole civilization to be able to mount a trip to visit it, and when they arrive find it is all just a mock-up.
    - MattPalmer1086 5y ago
      Sure, there are good and interesting arguments as to whether anyone would bother, but that's orthogonal to whether we can distinguish them from natural sources. EDIT: but I like your idea, sounds like it would be a fun short story!
    - colordrops 5y ago
      Dyson, a very smart man, saw a reason to build them. Now there may have been some revelations since his time that have made it obvious that they are not a good idea, but clearly that information has not spread widely. Care to enlighten us?
mabbo 5y ago
A fun thought experiment to counter this idea. Let's presume that the universe is full of Dyson Spheres, and the gravity they produce is what we call "Dark Matter". Well, Dyson Spheres must be built, right? So earlier in time, there would be fewer of them, and later in time there would be more of them. When we look into the sky, we look back in time. So if this were the case, when we look backwards in time we should see more brightness and less dark matter effects, while closer in time we should see less brightness and more dark matter effects. We do not see those patterns. Dark matter is consistent over time, as far as we can tell, and brightness from stars remains what we would expect.

Could stars blacked out by Dyson spheres or other technology that completely harnesses their energy be an explanation for dark matter? Or would this matter not be so "dark" due to the heat signature?

awb 5y ago

I think most if not every galaxy has dark matter so if it’s Dyson spheres that would mean that nearly every galaxy was colonized with Dyson spheres in the same way (except ours because we don’t have evidence of a galaxy-wide civilization).

maxander 5y ago

Indeed, Dyson spheres would need to release some amount of waste heat, due to the laws of thermodynamics. If there were too many of them that heat would be visible (at least to infrared telescopes,) so we know that’s not the explanation for dark matter. Same with dust and other non-luminescent matter- it’s all way more visible than dark matter has to be, somehow.

freemint 5y ago
What prevents that waste head being as warm ad the peak in cosmic background background radiation
- ncmncm 5y ago
  Literally every last thing in the whole universe that can radiate heat is at least as warm as the cosmic background radiation. You cannot shed any heat at all unless you are warmer than the background radiation, because you would be absorbing as much heat from it as you radiate. If you were colder, you would necessarily be absorbing more. Thermodynamics does not play around.

buryat 5y ago

what would prevent an intelligent civilization from covering all other stars in dyson spheres? and the dark matter is everywhere (almost, there're galaxies without it) which would mean that most of the universe has intelligent life but then why there's no other signals? something should've leaked/pointed at it

ncmncm 5y ago
What would prevent it? Good sense. To be able to do it is to know better than to bother.

ncmncm 5y ago

In a word, no. Any sort of Dyson-spherish thing would radiate in infrared, and not be dark at all. A long time ago somebody went looking for these infrared emitters, and found billions (and billions) of them in our galaxy alone. Turns out low-grade infrared-emitting stars and star-like things are more common than dirt. There is no way to tell them apart from a hypothetical Dyson thingy, even if there were any actual reason ever to build one of those. (Which, hint, there isn't.)

MattPalmer1086 5y ago
The introduction to the article says: "The observational signatures of such “Dyson spheres” include waste-heat from the absorbing sphere, obscured direct star light (resulting in both an apparently underluminous star and potential temporal variations in brightness) and the effects of feedback on the properties of the star from the surrounding sphere." So there are ways to distinguish probable Dyson spheres from the majority of these natural infrared sources.
- ncmncm 5y ago
  That would depend on somebody, anybody seeing any reason to build so much as one of them. You might imagine a playful civilization building one next-system-over to fool planet-bound hicks who actually still believe they are a good idea. The hicks restructure their whole civilization to be able to mount a trip to visit it, and when they arrive find it is all just a mock-up.
  - MattPalmer1086 5y ago
    Sure, there are good and interesting arguments as to whether anyone would bother, but that's orthogonal to whether we can distinguish them from natural sources. EDIT: but I like your idea, sounds like it would be a fun short story!
  - colordrops 5y ago
    Dyson, a very smart man, saw a reason to build them. Now there may have been some revelations since his time that have made it obvious that they are not a good idea, but clearly that information has not spread widely. Care to enlighten us?

mabbo 5y ago

A fun thought experiment to counter this idea. Let's presume that the universe is full of Dyson Spheres, and the gravity they produce is what we call "Dark Matter". Well, Dyson Spheres must be built, right? So earlier in time, there would be fewer of them, and later in time there would be more of them. When we look into the sky, we look back in time. So if this were the case, when we look backwards in time we should see more brightness and less dark matter effects, while closer in time we should see less brightness and more dark matter effects. We do not see those patterns. Dark matter is consistent over time, as far as we can tell, and brightness from stars remains what we would expect.