12 ms·

"Equation" is an unfortunate name because some view that like the Drake Equation is meant to produce a quantifiable number. It isn't and never was. It's a thoug

by cletus 5y ago

"Equation" is an unfortunate name because some view that like the Drake Equation is meant to produce a quantifiable number. It isn't and never was. It's a thought experiment and a way to frame the problem (the article states this explicitly). What has changed is the assumptions about how we would detect a starfaring civilization. 60 years ago we were assuming radio communications because that seemed to be where our future was and, by extension, what we might expect other civilizations to do. Obviously the values in the equation are unknown. We use such things to frame problems that involve unknowns like this. A good example: the anthropic principle [1]. Anyway, the more prevalent line of thinking now is that starfaring civilizations are likely to end up building Dyson swarms. This is a long and complex discussion. There are many objections but those objections tend to suffer from the problem that, if that objection is true, there should be more not less starfaring life (eg any form of FTL). If matter is the ultimate limiter to civilizations then it makes sense that civilizations will try and amass as much of it as possible. It doesn't matter if not every civilization goes this route because even one such galaxy-spanning civilization within a million light years will stand out (based on the IR signature). Even without that it probably wouldn't take more than about 10M years for humanity to colonize the Milky Way. [1]: https://en.wikipedia.org/wiki/Anthropic_principle https://en.wikipedia.org/wiki/Anthropic_principle

LatteLazy 5y ago
Wait, do people actually think Dyson swarms are a thing? The amount of time and energy needed to build them always seemed ridiculous to me. Especially as all you gain is energy (which hasn’t proven limiting) and you lose almost everything else (gravity and atmosphere for a start)...
- mgolawala 5y ago
  I am not at all well informed about this but I imagined a Dyson swarm would sort of grow and evolve organically over time. Not as an end goal in themselves. For example, if you start building space habitats (even if they are enclosed cylinders such that they hold an atmosphere and provide gravity via rotation) you need to put them somewhere. It makes sense to throw them in orbit around the star at some optimal distance (for example at 1AU +/- some amount), if you continue to put more and more such habitats around a star in similar orbits over time, in sufficient numbers, wouldn't they start to resemble a Dyson swarm?
  - cletus 5y ago
    Think of it this way: a cloud is just water droplets suspended in the air. The air is transparent. Water is transparent. Yet... you can't see through clouds. That's essentially what a full Dyson Swarm looks like. People have modeled how many orbitals you'd need to achieve this and I believe that if you orbit them at 1 AU (plus or minus) the mean distance between them is still around 150,000km.
- the8472 5y ago
  > Especially as all you gain is energy (which hasn’t proven limiting) What? Civilization runs on cheap, abundant energy. Before the industrial revolution we had to use labor animals, slaves and the occasionally water and wind mill. Providing light was expensive. Global supply chains (transportation), aluminium smelting, fixing nitrogen for fertilizer or calcination for cement consume stupendous amounts of energy. If energy became cheaper then creating green fuel for airplanes and rockets, electrorefining all metals, desalination or perhaps mining and crushing olivine rocks for carbon sequestration would become more feasible. Whenever vertical farming is discussed here the main counter-argument boils down to energy not being cheap enough. It's hard to compete with the sun delivering it to plants for free.
  - Grustaf 5y ago
    None of those things are necessary for civilisation, or radio communication. They just improve things on the margin. Besides, surely it must be simpler to build a fusion reactor on earth than harvesting enough material to cover the sun in solar panels. Would the solar system even have enough resources for that?
    - the8472 5y ago
      > None of those things are necessary for civilisation That's only true for low values of civilization. Even bronze age tech consumes more than hunter-gatherers which consume more than monkeys. > Besides, surely it must be simpler to build a fusion reactor on earth than harvesting enough material to cover the sun in solar panels. Dyson swarms sit higher on the kardashev scale than harvesting whatever you can get on a single planet. At some point waste heat rather than fuel will also become a real problem. Fusion reactors are ultimately thermal power stations, glorified steam engines. > Would the solar system even have enough resources for that? You'd start small with asteroids. And then disassemble some moons with shallow gravity wells. Which of course again requires stupendous amounts of energy just to move the material around but the sun still has billions of years left so there will be time to recoup that investment.
    - pie420 5y ago
      The sun is a large fusion reactor. Eventually you will run out of mass in the solar system to put in your fusion reactor, and then you'll resort to extracting energy from the natural fusion reactor. A Dyson sphere is a fusion reactor of sorts.
- cletus 5y ago
  > Wait, do people actually think Dyson swarms are a thing? Yes, absolutely. The main reason is that building orbitals is largely an engineering problem. You need a material no stronger than stainless steel. If graphite is feasible, it allows you to build bigger orbitals but it's not necessary. Compare this to a lot of other proposed megastructures like space elevators, which would take a material to build that doesn't currently exist. Also, to be clear, we're talking about Dyson _Swarms_. This is the original design idea that was called Dyson Spheres but that name is often not used because people mistakenly think we're talking about a rigid shell that encompasses a star. That is not and never was the intent. It's also impossible for many reasons. A Dyson swarm is simply a collection of orbitals. The great thing about it is you can also build it incrementally. Note that since these are spinning orbitals they have (spin) gravity and atmospheres. Energy is absolutely a factor here.
  - UI_at_80x24 5y ago
    >Also, to be clear, we're talking about Dyson _Swarms_. This is the original design idea that was called Dyson Spheres but that name is often not used because people mistakenly think we're talking about a rigid shell that encompasses a star. That is not and never was the intent. It's also impossible for many reasons. Thank-you for clearing this up for me. I made a post after you, but you addressed the issues that I discarded. I now know more then I did. Thanks!
  - LatteLazy 5y ago
    How do such small objects maintain their atmospheres? Also, to remain in a stable orbit, wouldn't the spin force have to match the gravity of the star? So there would be no effective force left to provide gravity would there? (Similar to how people on the ISS are weightless despite still being within earth's gravity well).
    - pixl97 5y ago
      The vast majority of devices in a theoretical dyson sphere are energy collectors. These would be mostly flat with no atmosphere or gravity. Much larger 'space stations' could be built throughout the swarm that would have induced gravity or internal atmosphere.
- UI_at_80x24 5y ago
  I liked that Ringworld addresses this. What Dyson Sphere's excel at is hiding their location* and capturing 100% of a stars output. At those sizes, a civilization MUST have already conquered the energy problem. It'd be impossible to construct without "free energy", because you need to convert that energy into matter to make/engineer enough material to create a sphere the size of the Goldilocks zone. And as you said, you'd lose atmosphere & gravity* would be wonky. But to address the fine article, the equation was a thought experiment. We now have hard data on the number of stars that we've looked at that have planets. And of those we have a hard number that have planets in the habitable zone. The Drake Equation presumes that you guess TINY numbers for those values. Well using known numbers and extrapolating the number of possible worlds with intelligent life jumps from staggering large, to incomprehensible. As humans, we can barely communicate with others of our own species. Let's frame the problem another way. Put two Americans in a room. One is deaf, the other is blind. How long does it take for them to agree on what to eat for dinner? Context depends on language. We may have been bombarded by intelligent alien life for centuries; we just don't know that somebody is talking. *Everybody forgets about gravity.
  - the8472 5y ago
    > A civilization MUST have already conquered the energy problem There possibly are ever more exotic applications that require more energy. Energy to matter conversion which you mention (and which also conveniently produces antimatter) requires very very large amounts of energy. The mass defect of the Tsar Bomba is merely 2.6kg, which also happens to be roughly equivalent the energy the sun that hits the whole planet each second. And then there are speculative things like the alcubierre drive or anything that involves moving entire stars.
  - cletus 5y ago
    > I liked that Ringworld addresses this Just FYI, but the Ringworld as Larry Niven envisioned it simply doesn't work because no known or theorized material is remotely strong enough. To produce gravity a Ringworld needs to orbit the star. This produces centrifugal force that is tearing the ring apart. I believe around our Sun it would need to spin at about 1.2M mph [1]. [1]: https://www.bbc.com/future/article/20150609-will-we-ever-build-ringworlds#:~:text=Assuming%20that%20the%20ringworld%20shares,rotate%20at%20approximately%201%2C200%2C000mph https://www.bbc.com/future/article/20150609-will-we-ever-bui....
the8472 5y ago
Dissolving the Fermi Paradox[0] is a great and easy to read paper to disabuse anyone of the idea of multiplying point estimates when you could convolve probability distributions instead. [0] https://arxiv.org/abs/1806.02404 https://arxiv.org/abs/1806.02404
- floxy 5y ago
  I think this paper should be a top level HN discussion thread.
  - the8472 5y ago
    has been https://news.ycombinator.com/item?id=17560462 https://news.ycombinator.com/item?id=17560462
    - AceJohnny2 5y ago
      Almost 3 years old, it's a candidate for repost.
- robocat 5y ago
  I was confused by the line in the original article “by multiplying uncertain variables, the level of uncertainty grows exponentially, to the point where no firm conclusions are possible.” Because when I looked for an explanation, it wasn’t exponential: https://foothill.edu/psme/daley/tutorials_files/10.%20Error%20Propagation.pdf https://foothill.edu/psme/daley/tutorials_files/10.%20Error%...
analog31 5y ago
>>> 60 years ago we were assuming radio communications because that seemed to be where our future was and, by extension, what we might expect other civilizations to do. Indeed, and today, the bulk of our communications are via enclosed waveguides -- fiber optics. And our remaining wireless communications are quickly evolving towards both decreasing power use and signal formats that are nearly indistinguishable from noise. Our period of "hot" radio emissions may only span roughly a century.
- gus_massa 5y ago
  Once we go interplanetary, we will need to turn on the radio again.
  - simonh 5y ago
    Perhaps, but it's likely to be highly directional and it's possible we'll end up using lasers. Radio is really only viable at the moment because pretty much all communications goes to or from Earth (sometimes via relay) and on Earth we can build massive radio dishes to transmit very powerful signals, and enormously amplify reception. In the future a lot of comms will be between points other than Earth, and in many of those locations radio antennas many dozens of metres across won't be viable. I think at that point we'll most likely switch to lasers for communications over interplanetary ranges. Starlink are planning to use lasers for their sat-to-sat relay links.
JoeAltmaier 5y ago
Geometric growth would put it at far less than 10M years? On the order of hundreds of thousands I would think.
- cletus 5y ago
  The Milky Way is estimated to be ~100,000 light years across. We're not quite on the edge but we're closer to the edge than the center. So to colonize the galaxy you have to assume we'd need to travel almost 100,000 LY. If you assume moving at 1% of the speed of light, you come up with a lower bound of 10M years.
canadianfella 5y ago
FTL?

by cletus 5y ago

LatteLazy 5y ago

Wait, do people actually think Dyson swarms are a thing? The amount of time and energy needed to build them always seemed ridiculous to me. Especially as all you gain is energy (which hasn’t proven limiting) and you lose almost everything else (gravity and atmosphere for a start)...

mgolawala 5y ago
I am not at all well informed about this but I imagined a Dyson swarm would sort of grow and evolve organically over time. Not as an end goal in themselves. For example, if you start building space habitats (even if they are enclosed cylinders such that they hold an atmosphere and provide gravity via rotation) you need to put them somewhere. It makes sense to throw them in orbit around the star at some optimal distance (for example at 1AU +/- some amount), if you continue to put more and more such habitats around a star in similar orbits over time, in sufficient numbers, wouldn't they start to resemble a Dyson swarm?
- cletus 5y ago
  Think of it this way: a cloud is just water droplets suspended in the air. The air is transparent. Water is transparent. Yet... you can't see through clouds. That's essentially what a full Dyson Swarm looks like. People have modeled how many orbitals you'd need to achieve this and I believe that if you orbit them at 1 AU (plus or minus) the mean distance between them is still around 150,000km.
the8472 5y ago
> Especially as all you gain is energy (which hasn’t proven limiting) What? Civilization runs on cheap, abundant energy. Before the industrial revolution we had to use labor animals, slaves and the occasionally water and wind mill. Providing light was expensive. Global supply chains (transportation), aluminium smelting, fixing nitrogen for fertilizer or calcination for cement consume stupendous amounts of energy. If energy became cheaper then creating green fuel for airplanes and rockets, electrorefining all metals, desalination or perhaps mining and crushing olivine rocks for carbon sequestration would become more feasible. Whenever vertical farming is discussed here the main counter-argument boils down to energy not being cheap enough. It's hard to compete with the sun delivering it to plants for free.
- Grustaf 5y ago
  None of those things are necessary for civilisation, or radio communication. They just improve things on the margin. Besides, surely it must be simpler to build a fusion reactor on earth than harvesting enough material to cover the sun in solar panels. Would the solar system even have enough resources for that?
  - the8472 5y ago
    > None of those things are necessary for civilisation That's only true for low values of civilization. Even bronze age tech consumes more than hunter-gatherers which consume more than monkeys. > Besides, surely it must be simpler to build a fusion reactor on earth than harvesting enough material to cover the sun in solar panels. Dyson swarms sit higher on the kardashev scale than harvesting whatever you can get on a single planet. At some point waste heat rather than fuel will also become a real problem. Fusion reactors are ultimately thermal power stations, glorified steam engines. > Would the solar system even have enough resources for that? You'd start small with asteroids. And then disassemble some moons with shallow gravity wells. Which of course again requires stupendous amounts of energy just to move the material around but the sun still has billions of years left so there will be time to recoup that investment.
  - pie420 5y ago
    The sun is a large fusion reactor. Eventually you will run out of mass in the solar system to put in your fusion reactor, and then you'll resort to extracting energy from the natural fusion reactor. A Dyson sphere is a fusion reactor of sorts.
cletus 5y ago
> Wait, do people actually think Dyson swarms are a thing? Yes, absolutely. The main reason is that building orbitals is largely an engineering problem. You need a material no stronger than stainless steel. If graphite is feasible, it allows you to build bigger orbitals but it's not necessary. Compare this to a lot of other proposed megastructures like space elevators, which would take a material to build that doesn't currently exist. Also, to be clear, we're talking about Dyson _Swarms_. This is the original design idea that was called Dyson Spheres but that name is often not used because people mistakenly think we're talking about a rigid shell that encompasses a star. That is not and never was the intent. It's also impossible for many reasons. A Dyson swarm is simply a collection of orbitals. The great thing about it is you can also build it incrementally. Note that since these are spinning orbitals they have (spin) gravity and atmospheres. Energy is absolutely a factor here.
- UI_at_80x24 5y ago
  >Also, to be clear, we're talking about Dyson _Swarms_. This is the original design idea that was called Dyson Spheres but that name is often not used because people mistakenly think we're talking about a rigid shell that encompasses a star. That is not and never was the intent. It's also impossible for many reasons. Thank-you for clearing this up for me. I made a post after you, but you addressed the issues that I discarded. I now know more then I did. Thanks!
- LatteLazy 5y ago
  How do such small objects maintain their atmospheres? Also, to remain in a stable orbit, wouldn't the spin force have to match the gravity of the star? So there would be no effective force left to provide gravity would there? (Similar to how people on the ISS are weightless despite still being within earth's gravity well).
  - pixl97 5y ago
    The vast majority of devices in a theoretical dyson sphere are energy collectors. These would be mostly flat with no atmosphere or gravity. Much larger 'space stations' could be built throughout the swarm that would have induced gravity or internal atmosphere.
UI_at_80x24 5y ago
I liked that Ringworld addresses this. What Dyson Sphere's excel at is hiding their location* and capturing 100% of a stars output. At those sizes, a civilization MUST have already conquered the energy problem. It'd be impossible to construct without "free energy", because you need to convert that energy into matter to make/engineer enough material to create a sphere the size of the Goldilocks zone. And as you said, you'd lose atmosphere & gravity* would be wonky. But to address the fine article, the equation was a thought experiment. We now have hard data on the number of stars that we've looked at that have planets. And of those we have a hard number that have planets in the habitable zone. The Drake Equation presumes that you guess TINY numbers for those values. Well using known numbers and extrapolating the number of possible worlds with intelligent life jumps from staggering large, to incomprehensible. As humans, we can barely communicate with others of our own species. Let's frame the problem another way. Put two Americans in a room. One is deaf, the other is blind. How long does it take for them to agree on what to eat for dinner? Context depends on language. We may have been bombarded by intelligent alien life for centuries; we just don't know that somebody is talking. *Everybody forgets about gravity.
- the8472 5y ago
  > A civilization MUST have already conquered the energy problem There possibly are ever more exotic applications that require more energy. Energy to matter conversion which you mention (and which also conveniently produces antimatter) requires very very large amounts of energy. The mass defect of the Tsar Bomba is merely 2.6kg, which also happens to be roughly equivalent the energy the sun that hits the whole planet each second. And then there are speculative things like the alcubierre drive or anything that involves moving entire stars.
- cletus 5y ago
  > I liked that Ringworld addresses this Just FYI, but the Ringworld as Larry Niven envisioned it simply doesn't work because no known or theorized material is remotely strong enough. To produce gravity a Ringworld needs to orbit the star. This produces centrifugal force that is tearing the ring apart. I believe around our Sun it would need to spin at about 1.2M mph [1]. [1]: https://www.bbc.com/future/article/20150609-will-we-ever-build-ringworlds#:~:text=Assuming%20that%20the%20ringworld%20shares,rotate%20at%20approximately%201%2C200%2C000mph https://www.bbc.com/future/article/20150609-will-we-ever-bui....

the8472 5y ago

Dissolving the Fermi Paradox[0] is a great and easy to read paper to disabuse anyone of the idea of multiplying point estimates when you could convolve probability distributions instead. [0] https://arxiv.org/abs/1806.02404 https://arxiv.org/abs/1806.02404

floxy 5y ago
I think this paper should be a top level HN discussion thread.
- the8472 5y ago
  has been https://news.ycombinator.com/item?id=17560462 https://news.ycombinator.com/item?id=17560462
  - AceJohnny2 5y ago
    Almost 3 years old, it's a candidate for repost.
robocat 5y ago
I was confused by the line in the original article “by multiplying uncertain variables, the level of uncertainty grows exponentially, to the point where no firm conclusions are possible.” Because when I looked for an explanation, it wasn’t exponential: https://foothill.edu/psme/daley/tutorials_files/10.%20Error%20Propagation.pdf https://foothill.edu/psme/daley/tutorials_files/10.%20Error%...

analog31 5y ago

>>> 60 years ago we were assuming radio communications because that seemed to be where our future was and, by extension, what we might expect other civilizations to do. Indeed, and today, the bulk of our communications are via enclosed waveguides -- fiber optics. And our remaining wireless communications are quickly evolving towards both decreasing power use and signal formats that are nearly indistinguishable from noise. Our period of "hot" radio emissions may only span roughly a century.

gus_massa 5y ago
Once we go interplanetary, we will need to turn on the radio again.
- simonh 5y ago
  Perhaps, but it's likely to be highly directional and it's possible we'll end up using lasers. Radio is really only viable at the moment because pretty much all communications goes to or from Earth (sometimes via relay) and on Earth we can build massive radio dishes to transmit very powerful signals, and enormously amplify reception. In the future a lot of comms will be between points other than Earth, and in many of those locations radio antennas many dozens of metres across won't be viable. I think at that point we'll most likely switch to lasers for communications over interplanetary ranges. Starlink are planning to use lasers for their sat-to-sat relay links.

JoeAltmaier 5y ago

Geometric growth would put it at far less than 10M years? On the order of hundreds of thousands I would think.

cletus 5y ago
The Milky Way is estimated to be ~100,000 light years across. We're not quite on the edge but we're closer to the edge than the center. So to colonize the galaxy you have to assume we'd need to travel almost 100,000 LY. If you assume moving at 1% of the speed of light, you come up with a lower bound of 10M years.

canadianfella 5y ago

FTL?