[pharke]

If an advanced civilization continued to improve the efficiency of this effect would they eventually use it to capture the majority of the energy output of their local star? You could have a shell of high efficiency solar satellites surrounded by another shell of high efficiency Seebeck satellites. What would this look like from a distance? Would they be able to capture enough energy so their star would be indistinguishable from the ambient temperature of space?

Our galaxy and others appear to be missing most of the mass i.e. stars that they should have in order to rotate as fast as they do. We put the figure for missing mass at about 80 to 90 percent for our galaxy. What if our galaxy and others are already colonized by advanced civilizations that make maximal use of the power output of stars so it simply looks like we're missing most of the matter that should exist. This could explain why there is a variation in the amount of missing mass between galaxies with some galaxies apparently containing 0% 'dark matter'. No advanced civilization = no dark matter, different amounts = different stages in development of the galactic civilization.

Could this be a solution to the Fermi paradox?

[ailideex]

> Would they be able to capture enough energy so their star would be indistinguishable from the ambient temperature of space?

You would still see infrared:

https://en.wikipedia.org/wiki/Fermi_paradox#Conjectures_abou...

> Such a feat of astroengineering would drastically alter the observed spectrum of the star involved, changing it at least partly from the normal emission lines of a natural stellar atmosphere to those of black-body radiation, probably with a peak in the infrared.

https://en.wikipedia.org/wiki/Technosignature

> A Dyson sphere, constructed by life forms dwelling in proximity to a Sun-like star, would cause an increase in the amount of infrared radiation in the star system's emitted spectrum. Hence, Freeman Dyson selected the title "Search for Artificial Stellar Sources of Infrared Radiation" for his 1960 paper on the subject.[4] SETI has adopted these assumptions in its search, looking for such "infrared heavy" spectra from solar analogs. From 2005, Fermilab has conducted an ongoing survey for such spectra, analyzing data from the Infrared Astronomical Satellite.[5][6]

[Misdicorl]

Only if the 2nd law of thermodynamics holds. When speculating about advanced civilizations building Dyson spheres, why not speculate about the bedrock of science as well?

There are (probably) other paths to avoiding this conundrum as well. Spitballing here, but perhaps the 'satellites' in this case can be pairs of orbiting black holes which emit the waste heat in a band we don't detect (gravitational waves).

[pharke]

I always forget about the concept of gravitational engineering, probably because it's just a bit scary to think about the unknowns involved. If you could mass produce small black holes and position them you could pretty easily construct giant lenses capable of redirecting the output of a star to anywhere you please. That's more than a little terrifying.

[ailideex]

> Only if the 2nd law of thermodynamics holds. When speculating about advanced civilizations building Dyson spheres, why not speculate about the bedrock of science as well?

If the person I replied to qualified their comment with "lets assume laws of physicis is not relevant" then sure...

[Misdicorl]

Except when discussing technologically hyper advanced civilizations, the 2nd law of thermodynamics is a (vaguely) reasonable place to expect our laws to break.

The 2nd law is an observed fact with very shaky theoretical underpinnings (I am not talking about the behavior which has very strong underpinnings). It appears to be an emergent behavior rather than a fundamental one. It is a surprising fact given what else we know about the universe. It breaks the time symmetry of the other laws of physics. This is akin to learning that even though the laws of physics dont break position and rotational symmetries, there is a preferred direction and spin. In fact there is a preferred spin- all neutrinos are left handed. There are huge research efforts to understand why or if there are corresponding right handed particles. Broken symmetries mean big things because as far as we can tell the universe is ruled by what symmetries exist and in what ways they are broken.

[pharke]

You're ignoring the point I was making about capturing the infrared waste heat. It seems counterintuitive for a civilization to go to the effort of encasing their star in a shell of satellites while dumping energy as waste heat. Surely there must be some way of utilizing that energy and my conjecture was that advances in the efficiency of the Seebeck effect might lead to a way to fully utilize that waste.

[Dyonisus]

If we look at our planet, we should realize that fossils and nuclear power are limited. Aside of the quantitative limitation, we get to feel the negative green-house effects now, making alternative energy sources even more urgent. The only real long-term source is the sun. We HAVE to (completely) switch to sun energy within the next 100 years. This will require huge photon harvesting facilities. For now, covering our deserts would be enough. But what if our energy requirement increases 10 fold? The more energy we have, the more people can have steaks and luxury. In the SECOND we reach the point of energy limitation on Earth, we will expand our photon harvesting facilities into space, close to Earth. This will grow with generations, so will technology. The gigantic amount of energy daily shining onto Earth is still ridicously few compared to what the Sun radiates every second. The photon harvesting layer will shrink, become more efficient, harvest more wavelengths (maybe even just a single atomic layer) and routed to central cores where it is collected and sent to Earth or the future intelligence habitat. Even if it is just a mirror, redirecting the photons to a central core, which routes it close to Earth, where it will evaporate water - or whatever much smarter ideas our future generations will find.

And this is what we could do now with our technology.

The infra-red issue, imho, is based on current technology level. No light enters the depth of the ocean because life evolved to build photon-recepters of all wave-lengths, even the less fruitful.

Taking this into consideration, every maturing civilization WILL inevitably produce Dyson spheres at least transiently. We already started it! Just look at the solar moduls of the ISS, which are actually the beginning of a Dyson sphere.

[bagacrap]

What would they use all that energy for, and how would they use it in a way that wouldn't radiate heat or light on par with the amount captured?

[pharke]

A good use might be computing power whether its for storing the minds of everyone in the civilization or powering one big mind or simulating universes or maybe it's all dedicated to finding a way to reverse entropy.

If we're assuming a highly advanced civilization aiming for maximal efficiency I would hope that they have figured out how to make all of their electrical systems out of high temperature superconductors.

[Matumio]

Is there really a way to "use" energy for computation that doesn't just convert all of it to heat?

[strbean]

Store it as mass!

[bwanab]

Sounds like a good beginning to a collaboration novel by Neal Stephenson and Alastair Reynolds.

[etimberg]

https://en.wikipedia.org/wiki/Dyson_sphere