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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 e

by jmyeet 5y ago

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.

pmoriarty 5y ago
"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.
slimsag 5y ago
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.
- kingcharles 5y ago
  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?
  - tomrod 5y ago
    Ennui seems motivating.
  - goatlover 5y ago
    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.
- colechristensen 5y ago
  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.
- oceanplexian 5y ago
  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.
asvitkine 5y ago
But do civilizations need that much energy?
- 0xBABAD00C 5y ago
  That's like asking "but do fires need that much wood", watching a fire spreading through a forest.
- jmyeet 5y ago
  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.
- deleted 5y ago
  [deleted]
- goatlover 5y ago
  If they wish to do things requiring that much energy.
gabereiser 5y ago
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 5y ago
  And worth doing because sometimes we get very lucky and stumble upon such surface fossils.
  - gabereiser 5y ago
    Sure, but usually you have to dig, even with surface fossils.
robonerd 5y ago
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 5y ago
  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.
heavyset_go 5y ago
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 5y ago
  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 5y ago
    > 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
andrewljohnson 5y ago
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 5y ago
> It is almost unfathomable what you could do with that much power. …Bitcoin?
- tomrod 5y ago
  We have pretty rocks that trade for much less transaction cost. Let's use those as currency versus consuming entire stars!
taotau 5y ago
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'.
goatlover 5y ago
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 5y ago
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.
Simon_O_Rourke 5y ago
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.
Balgair 5y ago
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.
Lutzb 5y ago
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.

by jmyeet 5y ago

pmoriarty 5y ago

"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.

slimsag 5y ago

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.

kingcharles 5y ago
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?
- tomrod 5y ago
  Ennui seems motivating.
- goatlover 5y ago
  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.
colechristensen 5y ago
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.
oceanplexian 5y ago
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.

asvitkine 5y ago

But do civilizations need that much energy?

0xBABAD00C 5y ago
That's like asking "but do fires need that much wood", watching a fire spreading through a forest.
jmyeet 5y ago
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.
deleted 5y ago
[deleted]
goatlover 5y ago
If they wish to do things requiring that much energy.

gabereiser 5y ago

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 5y ago
And worth doing because sometimes we get very lucky and stumble upon such surface fossils.
- gabereiser 5y ago
  Sure, but usually you have to dig, even with surface fossils.

robonerd 5y ago

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 5y ago
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.

heavyset_go 5y ago

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 5y ago
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 5y ago
  > 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

andrewljohnson 5y ago

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 5y ago

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

tomrod 5y ago
We have pretty rocks that trade for much less transaction cost. Let's use those as currency versus consuming entire stars!

taotau 5y ago

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'.

goatlover 5y ago

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 5y ago

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.

Simon_O_Rourke 5y ago

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.

Balgair 5y ago

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.

Lutzb 5y ago

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.