[zare_st]

A hypothetical megastructure Dyson's sphere would not radiate heat. And I'm not so sure that you can apply the stealth principle here. Stealth inhibits active measurement and astronomical measurements are passive. We have sensor resolution and we have a mass of data to sift through - each time sensor generation or data processing advances, we see stuff we haven't seen before.

The data is analyzed as a dynamic system. Radar just looks at a bounce. If you setup radar incorrectly you might get false hits and no returns on valid targets. If you use a wrong model in analysis of astronomical data you're never getting anywhere close to a correct result.

[cwillu]

A Dyson's sphere is a device to convert high frequency photons (visible light and uv) to low frequency photons (radiated “heat”). A sufficiently deep stack of shells can bring the temperature of the radiated light closer to the temperature of the cosmic background radiation, but it absolutely will radiate.

[zare_st]

Which is exactly my point.

The question isn't whether Dyson speheres radiate, the question is can we detect an artificial megastructure and my answer is no, based on the hypothetical Dyson design.

[cgriswald]

That is physically impossible unless there is new physics in that hypothetical design. All physical objects radiate heat and a Dyson sphere in particular would be trivial to detect. You look take a picture of the sky in infrared and in the visible spectrum. If you find an infrared source but no associated visible star you’ve got a strong candidate for being a Dyson sphere. Such searches have actually been conducted.

Other megastructures might be discovered through the same methods as exoplanets.

[JPLeRouzic]

> If you find an infrared source but no associated visible star you’ve got a strong candidate for being a Dyson sphere

You mean like brown dwarfs?

[cgriswald]

Yes, but a Dyson sphere, even around a red dwarf, would be far more luminous in the infrared than a brown dwarf. It would also have a different spectrographic signature, and importantly its heat distribution would appear artificial.

[wolfram74]

Rough calculation get's me a dyson sphere big enough to bring the black body radiation of the sun down to ~4k being hundreds of times the orbit of pluto. At that point it's actually an interesting question of where you get all the mass for the nesting shells.

R_sol^2T_sun^4 = R_shell^2T_cmb^4 (R_sol^2*(T_sun/T_cmb)^4)^(1/2) ~= 2 light months.

[mattashii]

> A hypothetical megastructure Dyson's sphere would not radiate heat

Could you elaborate why not? All current technology I know of has an efficiency of <100%, with waste energy being lost as heat (which in space would be radiated away in the infrared spectrum). Why would this not be the case for a hypothetical dyson sphere or swarm?

[zare_st]

Because the topic isn't about heat per se but heat signatures and detecting artificial heat signatures across the universe.

Of course everything radiates heat I did not think I have to get down to that level in commenting here.

[yreg]

Sorry, I don't understand you either. Without new physics Dyson spheres radiate heat. Therefore they are detectable.