A thing I’m still not sure about reading that is “what percent of the light is getting through?”. Like, how dense are the reflector modules?
Later in the paper it says “The Dyson sphere is assumed to have an efficiency of one third”, which could mean “realistically you only capture about 1/3rd of the energy in the first place” or “the capturing/redirecting process” loses 2/3rds of the energy.
They’re probably basing their calculation on the orbital design discussed in citation 34: Suffern’s Some Thoughts on Dyson Spheres whose abstract says
According to Dyson (1960), Malthusian pressures may have led extra-terrestrial civilizations to utilize significant fractions of the energy output from their stars or the total amount of matter in their planetary systems in their search for living space. This would have been achieved by constructing from a large number of independently orbiting colonies, an artificial biosphere surrounding their star. Biospheres of this nature are known as Dyson spheres. If enough matter is available to construct an optically thick Dyson sphere the result of such astroengineering activity, as far as observations from the earth are concerned, would be a point source of infra-red radiation which peaks in the 10 micron range. If not enough matter is available to completely block the stars’ light the result would be anomalous infra-red emission accompanying the visible radiation (Dyson 1960).
Bolded for your convenience. Presumably they justify that assertion somewhere in the paper.
Imperfect efficiency isn’t because it’s transparent (as everyone keeps trying to say, it doesn’t have to let through any sunlight at all) - it’s because of Carnot efficiency. If you want to convert sunlight into electrical energy, you can’t do it perfectly, which means your Dyson swarm heats up, which means it radiates light in the infrared.
So if 2⁄3 of the sun’s energy is getting re-radiated in the infrared, Earth would actually stay warm enough to keep its atmosphere gaseous—a little guessing gives an average surface temperature of −60 Celsius.
So if 2⁄3 of the sun’s energy is getting re-radiated in the infrared, Earth would actually stay warm enough to keep its atmosphere gaseous—a little guessing gives an average surface temperature of −60 Celsius.
That is, until the Matrioshka brain gets built, in which case assuming no efficiency gains, the radiation will drop to 44% of its original, then 30%, then 20%, etc.
A shell in a Matrioshka brain (more generally, a Dyson sphere being used for computation) reradiates 100% of the energy it captures, just at a lower temperature.
Yeah, the energy radiated to infinity only gets reduced if it’s being used for something long-term, like disassembling the sun or sending off energy-intensive intergalactic probes.
A thing I’m still not sure about reading that is “what percent of the light is getting through?”. Like, how dense are the reflector modules?
Later in the paper it says “The Dyson sphere is assumed to have an efficiency of one third”, which could mean “realistically you only capture about 1/3rd of the energy in the first place” or “the capturing/redirecting process” loses 2/3rds of the energy.
They’re probably basing their calculation on the orbital design discussed in citation 34: Suffern’s Some Thoughts on Dyson Spheres whose abstract says
Bolded for your convenience. Presumably they justify that assertion somewhere in the paper.
Imperfect efficiency isn’t because it’s transparent (as everyone keeps trying to say, it doesn’t have to let through any sunlight at all) - it’s because of Carnot efficiency. If you want to convert sunlight into electrical energy, you can’t do it perfectly, which means your Dyson swarm heats up, which means it radiates light in the infrared.
So if 2⁄3 of the sun’s energy is getting re-radiated in the infrared, Earth would actually stay warm enough to keep its atmosphere gaseous—a little guessing gives an average surface temperature of −60 Celsius.
That is, until the Matrioshka brain gets built, in which case assuming no efficiency gains, the radiation will drop to 44% of its original, then 30%, then 20%, etc.
A shell in a Matrioshka brain (more generally, a Dyson sphere being used for computation) reradiates 100% of the energy it captures, just at a lower temperature.
Yeah, the energy radiated to infinity only gets reduced if it’s being used for something long-term, like disassembling the sun or sending off energy-intensive intergalactic probes.