[yreg]

Even if interstellar travel is impractical, an advanced expansionist civ would be interested in building megastructures. And since there is no stealth in space (unless you can somehow mask heat), they should be observable.

Ofc there are explanations for that part of the paradox as well, but the impractical travel theory doesn't cover it.

[simne]

> no stealth in space (unless you can somehow mask heat)

I know two things.

1. We are now already using heat mask measures, even when we are very young civ in terms of Kardashev scale. We already use simple slit heat emitters in military tech (many Stealth planes have slit nozzles and for example, Leopard tanks also use slit exhaust for same reason).

2. Even we now know about possibility of laser heat, which could emit heat directly with very high focus.

In conclusion, idea is, to surround whole civ with heat mask blanket, and make all heat exhausts directly focused on directions, where now observer expected.

Second, looks like our development now is very slow, because it should be on early stages (Kardashev scale), and old civ's should know this.

And I now support theory, that we are fortunate to be far enough, so stronger civ's are not interested in spending resources to limit our development.

I even consider might be exists some preservation pact between Big civ's, to avoid touch young civ's, for some purposes like scientific, or arts. So yes, basically, I support Zoo theory.

[ben_w]

> In conclusion, idea is, to surround whole civ with heat mask blanket, and make all heat exhausts directly focused on directions, where now observer expected.

Although focussing emissions (not really a blanket) is possible, not only would some specific civilisation have to actually do that, it would have to be a common enough choice that every example we would otherwise have been able to see actually does choose to do that that — this gets increasingly difficult the more such examples there are: if a civilisation can build a Dyson swarm, what are they afraid of that they would want to hide? Even if one civilisation has a reason, everyone has to make this decision, regardless of how many (or few) "everyone" is.

"Dark forest" is a bad reason, as everyone with a Dyson swarm will have been able to know your planet existed and had life on it even when it was all single-cell species; a star winking out of existence is noteworthy, and easily noticed[0].

One Dyson swarm is enough to directly colonise a high percentage of all galaxies that aren't beyond the "reachable horizon"[1] of the universe. As soon as we can make artificial self-replicating machines (we know such machines can be made because all life is self-replicating nano-machines, we just don't know enough to do it completely from scratch yet), this would take us about 31 years[2] to make such a swarm.

[0] So easily noticed that we have, in fact, noticed it: https://vascoproject.org/vanishing-stars/

[1] the "reachable horizon" is how far stuff can get from here starting now given the universe is expanding and no FTL: https://upload.wikimedia.org/wikipedia/commons/8/88/Home_in_...

[2] https://www.lesswrong.com/posts/DvQ7cYxhnrZtWngvW/how-to-tak...

[simne]

> this would take us about 31 years[2] to make such a swarm

They assume, when have already working general AI technology and it have some limited size (volume-mass-energy consumption).

Unfortunately, we still not have GAI and even cannot predict, how large will be first practical unit.

Must admit, looks like we very close to do it, but from history of previous great technical inventions, some things takes decades to achieve production status and was repeatedly reinvented in some years after another inventor fail.

[ben_w]

General AI is unnecessary. Bacteria do not possess this trait, and yet reproduce themselves, some in as little as 30 minutes.

It is also possible to have a large system where humans are just a component, if this were necessary. The human-machine ratio is a function of how close the automation you have is to what you need.

[simne]

> Bacteria do not possess this trait, and yet reproduce themselves

If you programmer, you should know from experience or from learn, that in complex system possible just two ways to achieve reliable execution.

1. Brute force, just test as many possible scenarios as could, 99.999% is better than 99.99%, and make script for each scenario.

2. Smart, run system when tested somewhere between 70..90% and make some sort of insurance, so when happen non-tested scenario and all failing, you will pay (compensate) for harm, and make additions.

That is. Bacteria lives in comfortable environment (mostly in liquid water drop), and spent billions of slightly modified reproductions, to make solutions for all possible scenarios. You may hear, DNA of simplest bacteria are more than Million pairs, that's because of number of scenarios it successfully survive.

Space is much less comfortable environment than liquid water, it have wide range of possible parameters, I even not sure if exists some structure, which could survive in all possible space environments, so need some adaptation mechanisms, to change structure, and best is consciousness AI, which could make smart predictions of causes and reasons, and control all these machinery. And also it will have memory, to repeat moves which helps to survive when something similar happens earlier.

[ben_w]

> If you programmer, you should know from experience or from learn, that in complex system possible just two ways to achieve reliable execution.

Irrelevant. A self-replicating system does not need to be highly reliable. Look to the past, any time over 200 years ago most families were a dozen kids because most didn't reach adulthood.

> That is. Bacteria lives in comfortable environment (mostly in liquid water drop), and spent billions of slightly modified reproductions, to make solutions for all possible scenarios. You may hear, DNA of simplest bacteria are more than Million pairs, that's because of number of scenarios it successfully survive.

False. Bacterial environments are hostile because other bacteria fight them for the same resources, including predation. Many chemicals are hazardous even in small quantities. Internal chemistry requires water in liquid form, yet there's only a narrow range of temperatures where water is liquid, and worse the chemical processes change rate significantly even within that range.

Also irrelevant, we've been using simulated evolution as a form of AI for ages already. It's not new or novel. I implemented a version of this in 30 minutes over a decade ago just to prove a point. A million bases is trivial to store, so is a billion or a trillion.

> Space is much less comfortable environment than liquid water, it have wide range of possible parameters, I even not sure if exists some structure, which could survive in all possible space environments, so need some adaptation mechanisms, to change structure, and best is consciousness AI, which could make smart predictions of causes and reasons, and control all these machinery. And also it will have memory, to repeat moves which helps to survive when something similar happens earlier.

Also false.

1. Space has far fewer parameters than water.

2. One does not need to make a single machine to survive "all possible space environments" to do this, just our solar system at 0.47-0.31 AU from the sun. We already have that, we sent probes there.

3. Consciousness is not necessary for any of that. Neither is episodic memory (though that is trivial to implement). Bacteria exist and do these things well enough with mere DNA.

[simne]

BTW if you really know, you could make GAI for some reasonable amount of money, or you know people, who have this knowledge, I know few very serious people, who want to invest into such thing and have money.

[shrimp_emoji]

You're implying we'd easily see megastructures. Believe it or not, there's many more stars we haven't inspected than have. And our telescopes suck too much to see all but the largest megastructures, which you're assuming it would make rational sense to build in the first place. There can be better things for an economy to spend its (always finite) resources on.

[yreg]

> which you're assuming it would make rational sense to build

Yes I mean why not. If you are an expansionist advanced civ, travel is impractical and you have enought time and resources then what else is there to do?

Obviously there are explanations "why not" (as I said), but insterstellar travel unavailability is not one of them.

[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.