[jmyeet]

Not the first time I've said this but it's highly unlikely that we'll detect technological civilizations through radio emissions. We've had this kind of radio emission but it's incredibly brief so for Earth, you'd have to be listening for a few decades over the billions of years Earth has existed. That's incredibly unlikely.

The far more likely detection method is IR signatures, specifically from Dyson Swarms. A Dyson Swarm is not a rigid sphere (a confusion caused in part by the original name "Dyson Sphere"). It is a collection of orbitals with the intent of making full use of a star's energy output. The beauty of this is it's all rather low-tech needing little more than solar power, stainless steel level materials science and (this is the big one but is an engineering problem not a science one) getting access to basic raw materials.

Just like a cloud looks solid despite being water droplets, a complete Dyson Swarm would be the same. The visible light would be blocked out.

But here's where the IR part comes in. The only way to dissipate heat in space is to radiate it away. A habitat will have to do this. At any reasonable temperature the signature of that radiated heat is as IR radiation determined by the temperature of the radiating object. That's physics.

So if you see stars with low visible light output but shines like a beacon in the IR specturm (comparatively) that's a good candidate for a Dyson Swarm because stars don't otherwise look anything like that. This is what makes any "Hidden Aliens" type scenarios rather implausible. You just can't hide these things.

Let me add this perspective: on Earth we consume (IIRC) about 10^11 Watts of energy. The Sun's energy output is in the order of 10^26 Watts. It is almost unfathomable what you could do with that much power. That's using humanity's entire energy consumption about every 30 nanoseconds.

So what's more likely: 1. Detecting a few decades of radio emissions or 2. the IR signature of what would likely be millions of years?

So I applaud any investigation into the wow! signal just like I do of FRBs. We should understand likely causes but technological life? It almost certainly isn't.

[slimsag]

No stake in this game, but your likeliness assumption depends on the idea that a civilization could get to the point of creating a Dyson Swarm. If civilizations are statistically likely to destroy themselves before then, 'detecting a few decades of radio emissions' could be the only scenario.

[oceanplexian]

Or civilizations find a better way to generate energy.

Why would you build this big mass around a star when you can create your own, much more efficient fusion reactor where and when you need it? Stars are insanely inefficient; they convert less than 1% of their mass into energy, take billions of years to do it, and you can’t turn them off when you aren’t using them. Plus, if you wanted to use it for some exotic warp drive or something, you would have to haul the mass of a star around. None of it really makes sense to me.

[dividedbyzero]

Or civilizations stop growing and never get to a Dyson something stage. You're a hundred billion or so immortal beings that can engineer their very wants and propensities, with a trillion autonomous robot minions, near-inexhaustible amounts of raw materials from asteroids, and more than enough renewable energy to live very happily ever after, why keep growing? Maybe the great filter is just that, a shift in priorities that prevents the others from getting big enough to be easily detectable.

[jmyeet]

The most likely alternative energy soruce is fusion. Personally I'm not convinced this will ever be commercial. I'm not saying it won't be but there are huge problems to overcome, most notably destroying the container and plasma turbulence.

We already have the tech for space-based solar. Putting it in space makes it much more efficient. It's relatively low tech and doesn't require exotic materials or solving the massive engineering problems that fusion (for example) does.

Then there are other way more exotic methods (eg antimatter, black holes).

But all this misses the point. If you generated 10^26 Watts of power on Earth using fusion power you would still need to dissipate that heat into space or you'd quickly cook the Earth. So you're pretty much back to where you started.

What I like about the Dyson Swarm idea is that it requires no new physics and is relatively low-tech. So even if there is something far-future that's an option (eg antimatter, black holes) you have to ask questions like: Will everyone reach that point? Will civilizations build Dyson Swarms as an intermediate step anyway? How long is that reality? Will there still be a mixed-use future with both space-based solar and exotic enegy generation?

The Sun radiates a ton of energy into space. Capturing it is relatively simple. Dismissing that seems to defy credulity (IMHO).

[voldacar]

Yeah any civilization capable of building a dyson swarm could probably develop technology to dissasemble a star and use its matter for a more efficient nuclear process. I'm not sure how you would practically go about doing that though, a dyson swarm at least is relatively simple (in principle) to construct

[ajkjk]

"Disassembling a star" has to actually be possible in principle for this line of reasoning to make any sense.

[ceejayoz]

Oh, we've plenty of evidence of that going on.

https://arstechnica.com/science/2022/03/study-theres-no-blac...

> "Our best interpretation so far is that we caught this binary system in a moment shortly after one of the stars had sucked the atmosphere off its companion star, said co-author Julia Bodensteiner, an ESO fellow in Germany. "This is a common phenomenon in close binary systems, sometimes referred to as 'stellar vampirism' in the press. While the donor star was stripped of some of its material, the recipient star began to spin more rapidly."

[ajkjk]

Well, that's by another star, not by engineering.

[est31]

There are some sources that discuss the idea here:

https://sites.google.com/view/sources-stellar-engines https://www.youtube.com/watch?v=v3y8AIEX_dU

[voldacar]

the Caplan engine is quite nice! Assuming there is no need to move the solar system, it seems advantageous to dispense with the dyson sphere and just use the mechanism described to siphon out mass from the sun to directly power fusion reactors. Even a perfect dyson sphere captures <1% of the energy released by the sun's nuclear fusion.

[kibwen]

The efficiency of stellar fusion doesn't matter, only the cost does. Whether or not humanity decides to harvest it, the sun emits a ludicrous amount of energy for free, just waiting to be captured with today's tech.

Of course, you'd never want to actually use a Dyson Thing to ever transmit 100% of the Sun's energy to Earth, because all energy turns to heat eventually and you'd scour the planet clean from all the inevitable waste heat.

[chmod775]

> they convert less than 1% of their mass into energy

Isn't that about typical for fusion reactions? What are you fusing in your hypothetical reactor?

[maxerickson]

Get a star to eject mass is probably one of the more reasonable ways to go somewhere else in the galaxy.

You need a pretty big vessel to be self sufficient.

[Hydraulix989]

A star IS a fusion reactor

[colechristensen]

The second possibility is that there’s just another form of communication using a known or unknown physics phenomena which becomes common for long term usage. There’s this baked in presumption that we have discovered all of the basic technology and physics in the last couple hundred years that civilizations would be using for millions of years.

[jmyeet]

In the context of the Fermi Paradox, that's not really an issue. Let me explain.

Imagine the chance of a civilization getting from our point to a Dyson Swarm without destroying themselves is 1% for wahtever reasons you like. If there are 10,000 equivalents to us within 10,000 light years it becomes incredibly likely we won't see one of these. You can argue we're "first" but being "first" out of 100 or 10,000 civilizations gets unlikely.

Now imagine there are 5 instead of 10,000. Then not seeing any gets much more likely.

So my point is that not seeing any evidence of these so far is still evidence of something and that something is most likely to be that civilizations reaching even our point is rare.

As for destruction of a species at our point, that's a whole separeate avenue of discussion. But the short version is that this is incredibly likely. Even if all the superviruses get released and all the nuclear weapons get detonated humanity will still likely survive.

A lot of our advances were delayed not because that advance is hard but because we didn't know any better and just coming up with that idea is the problem. Once you know the structure of matter and ideas like smelting steel (which is realtively low tech) can be recovered way quicker than they're lost.

1,000 years ago we were throwing spears at each other. A little over 100 years ago we took our first flight. In the last 50+ years we've gone from landing on the Moon to reducing LEO payload costs from $50,000+/kg to arguably <$1,000/kg and it's likely in the next 20 years that'll come down to possibly as low as $100/kg.

Barring some cosmic catastrophe it seems that permanent habitation of orbitals within the next 1,000 is pretty conservative.

[wildermuthn]

Good explanation, but I disagree about the improbability of being “first”. Probability doesn’t apply when taking about why we are conscious at this moment in time. The same applies to the why I experiencing consciousness as a 21st century human verses a 50,000 BC human. Unless we propose that there is a unique pre-existing soul that gets assigned to a single human body out of every single human who will ever exist, consciousness is just a non-individualized phenomenon of the brain and has a 100% chance of existing for every human who will ever exist.

When you look at it this way, the idea of being “first” is actually the most simple solution to the Fermi paradox. It fits with what we see (or rather don’t see) without denying what history shows us: life seems to have sprung up quite easily on earth and by its nature is driven toward intelligence, insofar as intelligence is at root the capacity to predict and control the world around us. Non-intelligence can flourish as long as conditions in its world don’t diverge from the survival patterns encoded into biology. Only intelligence is capable of adapting to new and changing circumstances. Ironically, the harder it is for life to avoid annihilation, the more that evolution needs to select for intelligence. The same is true even for self-annihilation: we will have to be smarter to avoid it, not dumber.

Additionally, why would we expect earth to have evolved intelligent life if another intelligent species spread and settled across the galaxy?

The first ought to be the last.

[MR4D]

Not the OP, but if you think about it, putting devices at Lagrange points is in some ways the start of the process of building one.

The JWT is the most famous device at such a point, but there are a few others as well. [0]

The great thing about a swarm is that you can do it one at a time. Change the timescale to a thousand years or more, and there implied size even with our current level of tech would be nearly unimaginable compared to what we have today, while probably nowhere near a sphere.

[0] - https://en.wikipedia.org/wiki/List_of_objects_at_Lagrange_po...

— - - EDIT: meant to add - even if the world were destroyed today, the JWT would still transmit signals for some time (I don’t know it’s design lifetime, but likely years if not decades).

[Ekaros]

I'm not sure but there is question also about resources. Let's say we turn all rocky objects excluding most of Earth and our Moon in the solar system to Dyson swarm. Would this have any noticeable effect on how we show outwards? There is lot of dust around solar system already and asteroid belt is also there.

[jmyeet]

I've seen one estimate that 1% of Mercury's mass is sufficient to build a full Dyson Swarm around the Sun.

That's part of what makes Dyson Swarms attractive: planets are incredibly inefficent uses of mass in terms of living area created.

Why Mercury? It's metal-rich, has no atmosphere, has relatively low mass and energy is incredibly abundant due to proximity to the Sun.

Many seem to think we would need to dismantle the Solar System. We do not.

[kingcharles]

No stake, but what if a civilization just doesn't care any more? For instance, we all download our consciousness into the Singularity and our every wish is fulfilled. Why bother doing anything else as long as you have enough solar power hitting your planet's surface for whatever you are currently doing?

[goatlover]

This assumes everyone in the civilization would want to do that, including any AIs. We don't have an example for history or contemporary society where this is true. Not everyone wants to immerse themselves in digital entertainment, despite the proliferation of it. People engage in a wide range of activities, some of them which require deprivations and real danger, like climbing mountains. It would be odd if nobody from a civilization retained an interest in exploring space, with the possibility of finding something truly alien.

[tomrod]

Ennui seems motivating.

[zackees]

Funny how none of the solutions to the drake equation include the possibility that a government would hide evidence of alien life.

It’s literally more probable that all life in the universe dies than our government would cover up contact, according to the media.

[midasuni]

You assume mass competence of different governments in different countries over a dozen administrations. That’s a mass conspiracy theory, one which seems pretty much impossible.

[zackees]

And with all the media stories about alien life with laughable grainy footage of people walking in stilts and anal probes, what signal would you use to be able to determine what the "truth" is on alien contact? Would it be "your gut feeling"?

There's literally so much mainstream disinformation in the UFO space that there is zero chance that someone casually be able to figure out what's fact from fiction. The noise is so high that the signal is effectively buried.

So I disagree with your assessment that the truth would be viral. Most of the human population has already been inoculated to a viral UFO truth narrative.

[wincy]

I mean, it makes sense. If we had definitive proof that alien life existed a large portion of society would go absolutely bonkers. I'm pretty sure I would.

[heavyset_go]

The Dyson sphere hypothesis always bothered me because it rests on a lot of assumptions, most of them are anthropomorphic in nature, unless, of course, the hypothesis is only meant to recognize a very specific, human-like civilizations with human-like motivations and needs.

Who is to say that alien life would form human-like civilizations at all? Or that Dyson spheres are the "obvious" next steps for even our own civilization? Or that Dyson spheres would even suit the use cases of alien, or human, civilizations?

[jmyeet]

I disagree that it's human-centric.

Life seems way more likely to evolve in a gravity well. That creates certain constraints. Likewise, it's hard to imagine how life would become a spacefaring species without some form of social organization (ie they'd need to be social creatures).

And thing slike generating and using energy and creating living area also seem to be quite fundamental.

An alternative is for a meatbag civilization to go virtual. That's possible of course but computing power is a function of energy expenditure so you're kind of back where you started.

[mod]

> An alternative is for a meatbag civilization to go virtual.

Is there a name for this theory?

It seems inevitable to me, so I'm curious to hear the counter-arguments

[robonerd]

We know of one instance of a civilization broadcasting radio waves. But a Dyson Swarm has never been seen, it's purely speculative at this point. Uncertainty that Dyson Swarms ever exist changes the expected outcome of searching for them.

[analog31]

It's interesting that we're building a poor man's Dyson swarm of sorts. More and more of our communications are conducted along waveguides -- fiber optics -- that leak no signal. Remaining radio signals are being engineered to operate at lower power and be increasingly hard to distinguish from noise. And our long distance power transmission might switch to DC any day now. This took roughly a century from our first radio emanations, so the time frame for picking us up from a distance might be pretty short.

Another civilization might notice the IR signature of chemical changes to our atmosphere, as a clue that we're harboring intelligent life.

They probably assume that if we're smart, we're not going to try to communicate outside of our own solar system by radio. Even with a big enough antenna, radio signals eventually spread out and are governed by the inverse square law. We'd be better off sending out a matter-based container that remains intact along its journey, and can be programmed to engage in short-distance communications at its destination. Such a thing could also steer itself if it receives better information.

[Simon_O_Rourke]

I find the concept of Dyson swarms or spheres to be too grounded in what we humans would do now to capture that sort of energy. What are they going to use all that energy for anyway? We may as well discuss how alien civilizations handle mortgage interest rates.

We've got no concept of power requirements or generating capacity for even our own species given a few thousand years. No need to be projecting our own technology onto another potentially intelligent civilization.

[taotau]

Dyson swarms are fascinating concepts, but as we are learning about our own ever increasing energy requirements harvested from our ecosystem, moving around too much energy in a complex system can have undesirable consequences.

I would imagine that a planetary system as a whole has a 'climate' driven by it's host star, and redirecting large amounts of that energy would have unpredictable consequences. While most of the suns energy does leak off into interstellar space, before it reaches that point it interacts with various bodies big and small, solid and gaseous, it generates magnetic fields and powers phenomena we may not be aware of.

Perhaps the choice of creating a Dyson swarm IS the great filter, and any civilization that has achieved it finds itself in a state of 'solar climate crisis'.

[Balgair]

Whenever these discussions on mega structures come up I feel compelled to mention the ratios of mass-energy in the universe.

~5% of the universe is made up of the stuff you and I are. Most of that is hydrogen and helium, cooking in stars.

~20% of the universe is dark matter. We know very little about it except that it falls down.

~75% of the universe is 'dark energy'. I use quotes because we know almost nothing about it except that it seems to fall up (!?).

Give us another 500 years and who knows what the %s will look like. We could be missing dozens of whole categories still.

So when talking about aliens and hyper civilizations, I'm on the side that we know too little to even properly speculate. Like goldfish stuck in a pond.

That said, yeah, it's suuuuper fun to speculate about this stuff. I enjoy it a lot too.

[asvitkine]

But do civilizations need that much energy?

[jmyeet]

Energy is the ultimate limiting factor in everything we do. Cheaper and more abundant energy creates applications just like increasing bandwidth leads to new applications (eg video is really predicated on megabit+ connections).

But two things spring to mind:

1. Computing power. AGI is an obvious one. But can you imagine the virtual worlds people could lose themselves in or even live in permanently? and

2. Interstellar travel ie space highways. Curently interstellar travel is effectively predicated fusion power (or something more exotic) because of the reaction mass problem. But another possibility is concentrating sunlight to accelerate vessels out of the Solar System. This is currently the likeliest scenario for reaching a high percentage of light speed.

[0xBABAD00C]

That's like asking "but do fires need that much wood", watching a fire spreading through a forest.

[goatlover]

If they wish to do things requiring that much energy.

[goatlover]

The SETI assumption is that some alien civilizations want to make themselves known, and radio is the easiest way to do this. It would mean committing to a long term project of beaming powerful radio signals at candidate star systems. So we just need to scan radio frequencies for enough stars before we stumble across a beacon.

[bglazer]

Are there other phenomena that have similar affects on a star? Dust clouds?

I’m not really familiar with astronomy but I did follow the story around Tabby’s Star, which dimmed over a very short period. People threw around the idea of a Dyson swarm, but, I believe the most likely source of the dimming is believed to be a passing dust cloud.

[gabereiser]

I have come to the same conclusion. More than likely we’ll know about other civilizations not from radio waves but from either a celestial event they have created or by them visiting us (and letting us know).

Searching for radio waves is like digging for celestial dinosaurs without a shovel. Just hoping there’s a fossil on the top soil.

[jamiek88]

And worth doing because sometimes we get very lucky and stumble upon such surface fossils.

[gabereiser]

Sure, but usually you have to dig, even with surface fossils.

[pmoriarty]

"We've had this kind of radio emission but it's incredibly brief so for Earth, you'd have to be listening for a few decades over the billions of years Earth has existed."

This signal could have been repeating every 100 years for billions of years, for all we know.

[Lutzb]

The question is if we can direct the radiating of heat. So instead of an omnidirectional beacon it could be directed towards a target and as such reduce the probability of being detected.

[andrewljohnson]

you'd have to be listening for a few decades over the billions of years Earth has existed

Maybe all advanced civilizations are clustered around a certain time. It's less relevant how old the Earth than how old galactic civilization is.

[jkhdigital]

> It is almost unfathomable what you could do with that much power.

…Bitcoin?

[tomrod]

We have pretty rocks that trade for much less transaction cost. Let's use those as currency versus consuming entire stars!