I love this topic. If and when we detect a technologically-advanced civilization, I truly believe this is how we'll do it. But why? Because the Dyson Swarm (the preferred name; "sphere" implies a rigid structure that was never the intent) is seen by many as the most likely path forward for any spacefaring civilization. Why? Several reasons:
1. It can be built incrementally. What you'd probably do is build orbitals and put them in Earth's orbit around the Sun, Then you can keep adding new orbits. Ultimately you end up with a "cloud" of orbitals that will block a star's light in the same way that water molecules in a fog block light;
2. A likely candidate for an orbital is waht's called an O'Neil Cylinder: 3-4 miles in diameter, 10-20 miles long, producing Earthlike gravity on the interior by spinning. Smaller than this and it needs to spin too fast. Larger than this and you need stronger materials to stop it ripping itself apart from centrifugal forces. Stainless steel is sufficiently strong to build an O'Neil Cylinder;
3. Solar power is the most likely source for our future energy needs. It's the only known power source that directly creates power and it does so with no moving parts and no waste produced. In space, solar is so ridiculously efficient that it's unlikely fission could ever compete economically and fusion is still a pipe dream.
4. Approximately 1 in 10^9 of the Sun's output hits the EArth. That's an awful lot of "free" energy just radiating out into space. The growth potential is huge. What do we need all that energy for? History has shown we'll find a use but here's a big one: the energy cost of interstellar travel is so mind-boggling large that we'd need something like the Sun's energy output to do it. Plus an interstellar generation ship looks an awful lot like an O'Neil Cylinder.
Anyway, the article doesn't really explain why the seaerch for infrared radiation that I could see (maybe I missed it?). It's important.
A body in space like an O'Neil Cylinder will heat up, even with converting some of that energy to electricity. The only way to cool down in space is to either expel mater, which doesn't really scale, or to radiate it away into space. The wavelength of light from a radiating body is determined entirely by the temperature of that body and for any temperature we're likely to see, that means infrared radiation.
So if you look at a star with a near total Dyson Swarm you'll see much less visible light and much more IR radiation and there's really no way to hide that. Some might say you can capture the heat an turn it into energy but you can't do that with perfect efficiency (ie thermodynamics) plus the material of the orbital will just naturally radiate anyway no matter what you do.
It's extremely conservative to say that we'll have the technology to build and deploy an O'Neil Cylinder within 1000 years. Give it 10,000 years if you really want. It makes no difference. That's still the blink of an eye in cosmic terms. And that gap between having 1 and a billion is also the blink of an eye.
And once you have what's called a K2 (Kardashev-2) civilization (being one that uses the full energy output of a star) where interstellar travel becomes possible, even practical, seeding a new Dyson Swarm around another star becomes trivial and the proces continues to the point where 100 million years from now is a completely realistic time period to have a Dyson Swarm around every star in our galaxy.
A galaxy of Dyson Swarms would be so obvious to observers even millions of light years away, even at our current level of technology. The absence of seeing such a thing contributes to the idea that spacefaring life is incredibly rare.
"A likely candidate for an orbital is waht's called an O'Neil Cylinder: 3-4 miles in diameter, 10-20 miles long, producing Earthlike gravity on the interior by spinning. Smaller than this and it needs to spin too fast. Larger than this and you need stronger materials to stop it ripping itself apart from centrifugal forces. Stainless steel is sufficiently strong to build an O'Neil Cylinder;"
It's unclear what exactly you mean by "too fast", but assuming you're referring to human tolerances: human tolerances from NASA + Soviet studies put unambiguous, continuous tolerance without needing medication or training or anything else at 2rpm, which equates to a diameter of 450m. That is a lot smaller than an O'Neill cylinder and a lot more feasible to build sometime soon. IMO the best option is to build a 100m diameter testbed now from Earth materials, as the successor to the ISS. Then take the lessons learned there and build a 450m diameter prototype, which we can use space materials for if space mining has developed enough. We could technically throw enough material into orbit for a 450m diameter cylinder but it would be a lot of material. Any of the larger sizes and we'd need real-deal asteroid mining to make that happen.
Basically, build a small testbed now to conduct actual experiments on human health at different gravity levels + RPMs, and also start trying to figure out asteroid mining. Build a bigger prototype habitat once we can get materials for it, either from massive launch cost reductions or asteroid mining. After that point we really do need asteroid mining.
Well, so is building Dyson swarms and spheres. I'd bet that we will figure out fusion first.
> much more IR radiation and there's really no way to hide that.
Maybe you can create a black hole in orbit and radiate into that? I saw somewhere that it might be possible to create a black hole using less hydrogen than what is available on Earth.
> Well, so is building Dyson swarms and spheres. I'd bet that we will figure out fusion first.
Dyson Swarm doesn't require new technology. It is nothing but a collection of objects orbiting and gathering energy to power its own processes. We have satellites that orbit Earth but gather energy from the Sun.
By that yardstick fusion doesn't require new technology either. Humans successfully performed nuclear fusion many times since 1950s and there are thousands ready packaged fusion devices around the world.
Building a Dyson Swarm, which is really just the problem of creating one self-sustaining orbital (since after that it's just a scaling issue) is really just an engineering problem. A huge one of course but we already have teh technology to create a material as strong as stainless steel and to build solar power collectors.
Currently, the big cost is getting material into space. LEO payloads are still (AFAIK) >$1000/kg. Getting that to $100/kg or even $10/kg completely changes that equation and yes, there are viable paths to reach that (eg orbital rings).
Fusion isn't even an engineering problem yet: it's a science problem. The big problem is energy loss from neutrons (as well as those neutrons destroying your reactor). That's not a problem for stars. They have gravity and are simply so large that the vast majority of neutrons are captured and feed into the overall process.
It's not clear we'll ever reasonably solve these problems. A fusion reactor is large and expensive and has many moving parts since, ultimately, we just use heat to turn a turbine in the same way a coal or NG plant does. Plus it needs fuel. Over long timescales that's still a problem. What fuel? Helium-3 (for so-called aneutronic fusion) is a big problem to source. Deuterium is easy to get. Tritium is harder to get. Protium is obviously easy to get.
Nuclear power as it currently stands on EArth cannot compete with the cost of solar power with solar panel efficiency still going up. What happens to that when you put that solar panel in space and now it's producing ~7 times as much power since day/night and weather are no longer factors and there's no energy loss to the atmosphere?
This is why I say "if" nuclear fusion will ever be economically viable. I'm not saying it won't be but there are massive hurdles to even theoretical economic nuclear fusion.
A lot of thought has gone into this and other possible explanations. Isaac Arthur, of course, has an excellent video [1] on this issue. His entire library on the Fermi Paradox is worth watching.
The short version of why this seems unlikely is that there really is no hiding a K2 civilization for many reasons. For example, access to this much energy and having a megastructure as large as the Solar System (give or take) would allow you to create incredibly high resolution telescopes (with an without interferometry).
But consider this: if you, as a spacefaring civilization, want to be left alone, the best way to do it is to make sure nobody comes into your neighbourhood. If you "hide" that may happen accidentally. Isn't it better to advertise your presence and otherwise keep people away to avoid unintentional conflict?
Many challenges become a lot easier when you have 10,000x more energy. Start building Dyson satellites and you will quickly have the energy you need to create solutions for your problems
“The wavelength of light from a radiating body is determined entirely by the temperature of that body and for any temperature we're likely to see, that means infrared radiation.“
IR metamaterials change this, you can alter matter at the nanoscale and completely change it’s black body .
1. It can be built incrementally. What you'd probably do is build orbitals and put them in Earth's orbit around the Sun, Then you can keep adding new orbits. Ultimately you end up with a "cloud" of orbitals that will block a star's light in the same way that water molecules in a fog block light;
2. A likely candidate for an orbital is waht's called an O'Neil Cylinder: 3-4 miles in diameter, 10-20 miles long, producing Earthlike gravity on the interior by spinning. Smaller than this and it needs to spin too fast. Larger than this and you need stronger materials to stop it ripping itself apart from centrifugal forces. Stainless steel is sufficiently strong to build an O'Neil Cylinder;
3. Solar power is the most likely source for our future energy needs. It's the only known power source that directly creates power and it does so with no moving parts and no waste produced. In space, solar is so ridiculously efficient that it's unlikely fission could ever compete economically and fusion is still a pipe dream.
4. Approximately 1 in 10^9 of the Sun's output hits the EArth. That's an awful lot of "free" energy just radiating out into space. The growth potential is huge. What do we need all that energy for? History has shown we'll find a use but here's a big one: the energy cost of interstellar travel is so mind-boggling large that we'd need something like the Sun's energy output to do it. Plus an interstellar generation ship looks an awful lot like an O'Neil Cylinder.
Anyway, the article doesn't really explain why the seaerch for infrared radiation that I could see (maybe I missed it?). It's important.
A body in space like an O'Neil Cylinder will heat up, even with converting some of that energy to electricity. The only way to cool down in space is to either expel mater, which doesn't really scale, or to radiate it away into space. The wavelength of light from a radiating body is determined entirely by the temperature of that body and for any temperature we're likely to see, that means infrared radiation.
So if you look at a star with a near total Dyson Swarm you'll see much less visible light and much more IR radiation and there's really no way to hide that. Some might say you can capture the heat an turn it into energy but you can't do that with perfect efficiency (ie thermodynamics) plus the material of the orbital will just naturally radiate anyway no matter what you do.
It's extremely conservative to say that we'll have the technology to build and deploy an O'Neil Cylinder within 1000 years. Give it 10,000 years if you really want. It makes no difference. That's still the blink of an eye in cosmic terms. And that gap between having 1 and a billion is also the blink of an eye.
And once you have what's called a K2 (Kardashev-2) civilization (being one that uses the full energy output of a star) where interstellar travel becomes possible, even practical, seeding a new Dyson Swarm around another star becomes trivial and the proces continues to the point where 100 million years from now is a completely realistic time period to have a Dyson Swarm around every star in our galaxy.
A galaxy of Dyson Swarms would be so obvious to observers even millions of light years away, even at our current level of technology. The absence of seeing such a thing contributes to the idea that spacefaring life is incredibly rare.