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

Mon Oct 20 01:32:13 UTC 2025

-----Original Message-----
From: extropy-chat <extropy-chat-bounces at lists.extropy.org> On Behalf Of Keith Henson via extropy-chat
Sent: Sunday, 19 October, 2025 6:23 PM
To: John Clark <johnkclark at gmail.com>
Cc: Keith Henson <hkeithhenson at gmail.com>; ExI chat list <extropy-chat at lists.extropy.org>
Subject: Re: [ExI] Alien Civilizations May Only Be Detectable For A Cosmic Blink Of An Eye

 I am fairly sure that if you want a really large amount of low-error computation, it is better to run at a low temperature.  Current-day computers don't help that much in deciding how far out from the star you want to place a data center. Far out, they can be bigger without any structural issues.  Whatever is blocking light at Tabby's Star is
1.5 light seconds in diameter.

How many watts do you think it would take to run an uploaded human and simulate their environment?

Keith

Keith there is a tradeoff that Robert Bradbury and I argued about for years.  If the nodes in closer to the star, you have more energy per unit material, which is good, but it also gets hotter, which is bad.

Where Robert and I could never agree is in thickness.  He loved the idea of Matrioshka Brains because he did so much theoretical work on it, but he flatly refused to deal with (or even accept) thermal problems from the designs which had a significant thickness.

Without significant thickness, most of the star's energy passes right thru it.  This is OK, and helps keep everything cool, but it comes at the expense of speed: If a node can contact other nodes in any direction, it is good for speed, but bad for thermal dissipation.

spike

On Sun, Oct 19, 2025 at 2:46 PM John Clark <johnkclark at gmail.com> wrote:
>
> On Sun, Oct 19, 2025 at 3:16 PM Keith Henson <hkeithhenson at gmail.com> wrote:
>
>> > I expect we will eventually build data centers in space to accommodate trillions of uploaded humans.  I suspect they will be in the relatively cold "computational zone" where the lower yemperature reduces errors.
>
>
> The further from the sun your Dyson sphere (or Dyson swarm ) is, the more massive it has to be and the more difficult it is to build. If you build it from the distance the Earth is from the sun it would receive about 1360 watts of solar radiation per square meter. Assuming it's a blackbody you can figure out what its equilibrium temperature will be by using the formula T=(2σ)^1/4 where σ is the Boltzmann constant, and the "2" is in there because it radiates from both sides. Plugging in the numbers we get (1360/(2*5.67*10^-8))^(1/4)= 331 kelvins = 58 °C = 136 °F.
>
> Modern microprocessors typically operate between the temperatures of 30 and 85°C, so they should not malfunction at 58°C, thus I see no reason why you'd want to build a Dyson sphere with a radius larger than the Earth's radius around the sun.
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> John K Clark
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>
>>
>> I expect we will eventually build data centers in space to 
>> accommodate trillions of uploaded humans.  I suspect they will be in the relatively cold "computational zone" where the lower emperature reduces errors.
>>
>> As I have mentioned before, I hope there are no aliens; we don't need 
>> the competition.
>>
>> Keith
>>
>> On Sun, Oct 19, 2025 at 5:03 AM John Clark <johnkclark at gmail.com> wrote:
>> >
>> > On Sun, Oct 19, 2025 at 3:45 AM Keith Henson <hkeithhenson at gmail.com> wrote:
>> >
>> >> > wikipedis
>> >> "whereas Tabby's Star appears to be a normal F-type star 
>> >> displaying no evidence of a disc.[148]
>> >
>> >
>> > 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.
>> >
>> > 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.
>> >
>> > 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.
>> >
>> >  John K Clark
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>> >>
>> >> Keith
>> >>
>> >> On Sat, Oct 18, 2025 at 5:47 PM John Clark <johnkclark at gmail.com> wrote:
>> >> >
>> >> >
>> >> >
>> >> > On Sat, Oct 18, 2025 at 7:25 PM Keith Henson via extropy-chat <extropy-chat at lists.extropy.org> wrote:
>> >> >
>> >> >> > Tabby's star is well beyond the planet-making dust stage.
>> >> >
>> >> >
>> >> > There is no evidence of that. The sun is about 5 billion years old but Tabby's star is only about 1 billion years old. And the sun is only about 1 billion years older than the Earth. So Tabby is in its planet building stage.
>> >> >
>> >> > John K Clark
>> >> >
>> >> >
>> >> >
>> >> >>
>> >> >> On Sat, Oct 18, 2025 at 3:06 PM Adrian Tymes via extropy-chat 
>> >> >> <extropy-chat at lists.extropy.org> wrote:
>> >> >> >
>> >> >> > The same way that dust in most early solar systems sticks 
>> >> >> > around long enough to clump into planets, despite there being 
>> >> >> > an active star - more active at that time than later on - in the middle?
>> >> >> >
>> >> >> > On Sat, Oct 18, 2025 at 5:56 PM Keith Henson via extropy-chat 
>> >> >> > <extropy-chat at lists.extropy.org> wrote:
>> >> >> > >
>> >> >> > > How do you account for dust not being blown out of the 
>> >> >> > > system by light pressure like a comet tail?
>> >> >> > >
>> >> >> > > Keith
>> >> >> > >
>> >> >> > > On Sat, Oct 18, 2025 at 11:19 AM John Clark <johnkclark at gmail.com> wrote:
>> >> >> > > >
>> >> >> > > >
>> >> >> > > >
>> >> >> > > > On Sat, Oct 18, 2025 at 1:28 PM Keith Henson <hkeithhenson at gmail.com> wrote:
>> >> >> > > >
>> >> >> > > >> > How do you distinguish dust from computronium 
>> >> >> > > >> > discussed on this list
>> >> >> > > >> since sometime in the 1990s?
>> >> >> > > >
>> >> >> > > >
>> >> >> > > > Occam's razor. If simple and very common dust particles can explain the observed phenomenon, and it can, then why conjure up exotic and ultra complex computronium?
>> >> >> > > >
>> >> >> > > > John K Clark
>> >> >> > > >
>> >> >> > > >
>> >> >> > > >
>> >> >> > > >>
>> >> >> > > >>
>> >> >> > > >> Best wishes,
>> >> >> > > >>
>> >> >> > > >> Keith
>> >> >> > > >>
>> >> >> > > >> On Sat, Oct 18, 2025 at 3:36 AM John Clark <johnkclark at gmail.com> wrote:
>> >> >> > > >> >
>> >> >> > > >> > On Fri, Oct 17, 2025 at 11:35 PM Keith Henson <hkeithhenson at gmail.com> wrote:
>> >> >> > > >> >
>> >> >> > > >> >>> >>"That's why I think, at least in the observable universe, we are alone. "
>> >> >> > > >> >>
>> >> >> > > >> >>
>> >> >> > > >> >> > That's what I thought until the astronomers found almost 2 dozen blinking stars in a 2000 ly volume around Tabby's Star.
>> >> >> > > >> >
>> >> >> > > >> >
>> >> >> > > >> > That's an old claim from 2019, and even then the paper says the question of whether the 21 stars are really "Tabby-alikes" requires further investigation, but as of 2025 the claim remains unconfirmed and is now considered dubious by nearly all professional astronomers. The paper about the odd behavior of those 21 stars was based on data from a ground-based telescope over a period of just 11 months, but the data about Tabby's Star came from the Kepler space telescope over a period of 9 years and 7 months, so there was insufficient data to say that the two phenomenon were the same. And those 21 stars were "close" to Tabby in that they were near to it in the night sky as seen from earth, but that doesn't necessarily mean they were close to it physically.
>> >> >> > > >> >
>> >> >> > > >> > And the theory that the dimming of Tabby's Star is caused by an uneven cloud of small dust particles orbiting the star explains observations quite well, but the theory that the dimming is caused by a megastructure built by ET does not. In short, that 2019 paper has been largely superseded by subsequent astronomical research and astronomers have moved on to more interesting things.
>> >> >> > > >> >
>> >> >> > > >> > John K Clark
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>> >> >> > > >> >> > That makes absolutely no sense to me! What does AI have to do with it? It makes no difference if the brain that develops Drexler style Nanotechnology is wet and squishy or dry and hard because then they could make a von Neumann probe, and even if they couldn't move them faster than 0.001 C, which they almost certainly could, they could send one to every star in the galaxy in less than 50 million years (a blink of the eye cosmically speaking) and then a blind man in the fog bank could tell that the galaxy had been engineered. But even with our most powerful telescopes we've never seen a hint of such a thing. That's why I think, at least in the observable universe, we are alone.
>> >> >> > > >> >> >
>> >> >> > > >> >> >  John K Clark
>> >>

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