[ExI] Alien Civilizations May Only Be Detectable For A Cosmic Blink Of An Eye

[Keith Henson]

There is a world of difference between radiating a very small heat
leakage on the JWT and GW scale radiation from a power satellite.

If you want, I can send you an Excel sheet on radiation at various temperatures

It is a big problem with thermal-type power satellites when they go
into eclipse.  The steam freezes out, and they are hard to restart.

Keith

On Wed, Oct 22, 2025 at 3:48 AM John Clark <johnkclark at gmail.com> wrote:
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> On Tue, Oct 21, 2025 at 5:17 PM Keith Henson <hkeithhenson at gmail.com> wrote:
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>> > A hot heat sink is not desirable.
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> Sure, but that doesn't change the fact that the hot sun facing part of a planet still radiates away heat. The surface of Venus is at a scorching 464 C, but the planet is at thermal equilibrium so the amount of solar radiation energy it absorbs is still equal to the amount of heat energy it radiates away.
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>> > My work on low-pressure, low-temperature steam radiators optimised at 20 deg C.
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> Using no mechanical refrigeration and with just passive cooling (a.k.a. putting things in the shade) the James Webb telescope can get key components down to just 40 Kelvin or -233 C. And the telescope is only about 1% further from the sun than the Earth is.
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> John K Clark
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>> On Tue, Oct 21, 2025 at 5:57 AM John Clark <johnkclark at gmail.com> wrote:
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>> > On Mon, Oct 20, 2025 at 10:50 PM Keith Henson <hkeithhenson at gmail.com> wrote:
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>> >> > A heat sink facing the sun or a hot surface is not useful as a heat sink.
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>> > Yes it is. If you want to figure out how hot a planet is you've got to figure out how much solar radiation is being absorbed and how much is being radiated. If nothing is being radiated away, and the amount being absorbed is greater than zero, then the planet would keep getting hotter and hotter forever and its temperature would approach infinity. But that never happens.
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>> > John K Clark
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>> >> >> > That study is ancient, it's from 2016. Since then observations have shown that when the intermittent dimming of Tabby's Star occurs the dimming is much larger at short wavelengths of light than longer wavelengths, so whatever is causing the dimming it can NOT be a solid object, but it's just what you would expect from a dust cloud.  The visible light dimming is more pronounced than the infrared, it's more constant, but Tabby's Star produces more infrared light then you'd expect from a typical F-type Star, but it's what you'd expect if a dust cloud was involved.
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>> >> >> > Today the overwhelming consensus of astronomers and astrophysicists is that an uneven dust cloud orbits around Tabby's Star, although there is still debate about the exact nature of that cloud. Some think it's composed of comets and large fragments in the process of forming planets. But others think it is much younger than that and the dust is composed of the debris produced by the collision of two large planets. After all, something like that happened in the solar system, the moon is probably the result of a collision between the Earth and a Mars sized planet about 4.5 billion years ago, although in Tabby's case the planets involved would have been larger.
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>> >> >> > Also, Tabby's star is only about 1 billion years old, so it's very hard to believe a super advanced megastructure building life form could have evolved in such a short time, it would be amazing if even bacteria had. In fact it's very unlikely that complex life forms will EVER evolve around Tabby's Star because the Earth will become too hot for complex lifeforms to exist in about 500 million years, and the longevity of a star is inversely proportional to its mass take it to the power of 2.5, and Tabby's Star is 1.4 times the mass of the sun. Stellar lifetime =(Mass)^-2.5= (1.4)^-2.5 = 0.43.  So Tabby's Star will only live 43% as long as the sun, so forget about super intelligent beings, complex life forms such as worms would die of excess heat exhaustion just about the time they managed to evolve into existence.
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