[HN Gopher] Seven Dyson Sphere Candidates
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Seven Dyson Sphere Candidates
Author : sohkamyung
Score : 124 points
Date : 2024-05-18 10:28 UTC (12 hours ago)
(HTM) web link (www.centauri-dreams.org)
(TXT) w3m dump (www.centauri-dreams.org)
| illuminant wrote:
| I grow skeptical. Congruent planes of orbital accretion explain
| all this hype much better.
|
| The flat planier elliptical orbits (and planetary rings) come by
| millions of years of settling down of the otherwise chaotic
| convergence of material that created their systems.
|
| These readings that spark imaginations beyond science are yet
| chaotic systems (from whichever influence) that have not yet
| settled down (debre would be in irregular orbits.)
|
| As sciencey as finding a wormhole off the shoulder of Europa.
| alchemist1e9 wrote:
| > The flat planier elliptical orbits (and planetary rings) come
| by millions of years of settling down of the otherwise chaotic
| convergence of material that created their systems.
|
| I thought all of these seven are estimated to be old stars
| which such processes should have long ago settled down.
| malfist wrote:
| There's lots of reasons an old solar system can become
| chaotic again, assuming it ever became nonchaotic. Anything
| with sufficient mass or energy passing near or through the
| solar system would cause a lot of chaos
| illuminant wrote:
| *edit: Incongruent planes ...
| king_magic wrote:
| Very curious to see what other astronomers think about this in
| the comments. My gut feeling is there are almost certainly
| natural explanations for these. Just seems unlikely we would only
| be starting to see these now, even with the greater resolution of
| telescopes & increase in compute to crunch through the data.
|
| If there were 7 of these ripe for the plucking that were actual
| Dyson spheres, each one would be the single greatest discovery in
| all of humanity. Just seems a little too easy.
| malfist wrote:
| How does one tell the difference between a partial Dyson swarm,
| and occlusion by planetoids, especially in the early stages of
| development before the planets are formed
| MadnessASAP wrote:
| Well that is the question isn't it. And what the article
| tries to answer, or at least explore.
|
| Suffice to say the 7 candidates in the article do not
| conclusively have another explanation. Hence their status as
| Dyson sphere candidates.
| malfist wrote:
| Isn't that kindof a "god of the gaps" explanation? We don't
| understand it, therefore <something unprovable>
| Loughla wrote:
| I mean, if we have had breakthroughs in resolution and compute,
| and life really is everywhere, wouldn't it make sense that we
| would start finding these at some point? Why not right now?
| cletus wrote:
| Bayesian reasoning applies here. Natural phenomenon is the most
| likely cause.
|
| think of it this way: imagine in the future we travel to Alpha
| Centauri and find sentient life or even the remnants of such.
| That would be really bad. Why? Because if there are 2
| civilizations in our galaxy, how likely is it that they're next
| to each other? Incredibly unlikely. It heavily implies that
| sentient life is much more common. Now imagine if we find a
| third at, say, Barnard's Star.
|
| In Fermi Paradox terms this heavily implies that there is a
| Great Filter ahead of us and we're more likely doomed than not.
|
| Finding a Dyson Swarm near us has the same negative
| implications (for us), especially given that the gap between a
| partial or full Dyson Swarm and colonizing the galaxy is
| relatively small (~100 million yaers) in cosmic terms so how
| likely is it that we find a Dyson Swarm that is a) near us and
| b) in that narrow window between the emergence of spacefaring
| life and colonizing the galaxy.
| cletus wrote:
| 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.
| petters wrote:
| > and fusion is still a pipe dream
|
| 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.
| kiba wrote:
| > 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.
| varjag wrote:
| 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.
| cletus wrote:
| > Well, so is building Dyson swarms and spheres
|
| 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.
| elevaet wrote:
| The ultimate garbage dump
| asimops wrote:
| > The absence of seeing such a thing contributes to the idea
| that spacefaring life is incredibly rare.
|
| This could also be due to the fact that the dark forest
| hypothesis is correct.
|
| https://en.wikipedia.org/wiki/Dark_forest_hypothesis
| elorant wrote:
| The dark forest theory is about intentional communication. It
| doesn't say anything about technosignatures.
| cletus wrote:
| 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?
|
| [1]: https://www.youtube.com/watch?v=zmCTmgavkrQ
| le-mark wrote:
| Two of the big unknowns are zero g assembly, and delta v
| requirements to move near earth or earth crossing asteroids
| (iron rich) into suitable orbits.
|
| Certainly it's possible an asteroid munching, cylinder ring
| producing large machine in space can be conceived.
|
| Moving the material (or prefabbed rings) to the proper orbit
| seems like a large challenge.
| vitiral wrote:
| 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
| mensetmanusman wrote:
| "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 .
| lucubratory wrote:
| "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.
| tomtomistaken wrote:
| I still don't understand why you need to build a Dyson sphere and
| then transport the energy to where it's needed when you can build
| decentralized fusion reactors. What am I missing?
| MadnessASAP wrote:
| Can you build decentralized fusion reactors? This far the most
| efficient fusion reactor humanity has available to it exists
| approximately 1 AU away and is rather difficult to relocate.
| orbital-decay wrote:
| For comparison, how efficient is the biggest Dyson Sphere
| humanity built so far?
| vitiral wrote:
| Well we have a very incomplete but about 10-15% efficient
| Dyson swarm on earth with solar and wind farms. Now we just
| need to scale up.
| Karellen wrote:
| I thought the efficiency of a Dyson sphere/swarm was
| typically measured by how much of the star's total power
| was being used?
|
| We are not capturing 10-15% of the sun's total power
| output.
| vitiral wrote:
| Well, by that metric we have 0.0000000001% of a Dyson
| sphere created.
| aurareturn wrote:
| Pretty sure solar panels are 20% plus now with some much
| higher.
| vitiral wrote:
| Just did a Google search. Most cells which are actually
| produced are 10-11%.
| TheLoafOfBread wrote:
| That will be average efficiency, because during night
| solar panels usually don't work, unless you live in Spain
| https://www.nationalreview.com/planet-gore/scandal-solar-
| pow...
| kiba wrote:
| Don't forget the farms that feed humans and their farm
| animals.
| vitiral wrote:
| Well, the entire ecosystem and weather is fed by solar.
| It would be interesting to think about what it's
| "efficiency" would be...
| belter wrote:
| Which Lazarus Cycle are you referring to?
| tomtomistaken wrote:
| > Can you build decentralized fusion reactors?
|
| My guess is that if you can build Dyson spheres you can build
| fusion reactors.
|
| > This far the most efficient fusion reactor humanity has
| available to it exists approximately 1 AU away
|
| Efficient in terms of what? With what are you comparing it
| to?
| throwaway11460 wrote:
| Dyson spheres can be very low tech. To reiterate, it's a
| swarm of objects orbiting the star, not a rigid sphere.
|
| If you have the time and raw resources, it was possible
| with 1960s technology.
| varjag wrote:
| It was not possible at all with 1960s technology, nor it
| is possible today.
| fikama wrote:
| I guess he refers that the stars are only fusion reactors
| that are creating surpuls energy (more than is neede to
| sustain reaction)
| lucubratory wrote:
| The technology for a Dyson sphere is primarily the
| technology for suspension bridges, solar farms, and
| intensive hydroponics (all well understood) + the
| technology for the ISS (well understood at this point). The
| only missing piece there is a fully sustainable (i.e. only
| energy input) life support system, which we have existence
| proofs for on Earth but haven't built to reliable
| engineering standards yet. If we have the material, we
| could start building it today and get designs that worked
| well quickly, even if we had to ship in life support
| maintenance alongside computer chips & pharmaceuticals.
|
| The part we don't know how to do yet is getting the
| material. Building structures that large in space, the
| resources for it have to come from space, we cannot lift it
| off Earth. So we need to figure out how to mine asteroids,
| and maybe also how to mine Mercury. Either one would be
| sufficient at the start. Neither of those are a well-
| understood problem, let alone solved, so that's where you
| should invest resources if you're a billionaire looking to
| start a Dyson sphere and think SpaceX is on track for
| launch cost reduction.
|
| I think in terms of science and engineering difficulty,
| it's a pretty even race as to which is more difficult
| between making fusion actually produce net useful energy
| and being able to mine & refine materials from an asteroid
| + build a sustainable life support system.
|
| The reason fusion "seems easier" is because it is
| economically far more achievable, and there's a lot more
| political will behind it so it feels more possible.
| throwaway11460 wrote:
| As a billionaire that wants to start a Dyson sphere,
| where is the profit / operational revenue?
| lucubratory wrote:
| Who said anything about profit? This is legacy building,
| a reason to have gotten all that money and power.
| throwaway11460 wrote:
| This was not meant as a counter argument, I am interested
| in more on this topic. Legacy building seems like a good
| reason, but not scalable imho.
| lucubratory wrote:
| Well, I guess the argument would be that a billionaire
| financing the construction of space habitats could make
| them effectively company towns, but of a highly educated
| workforce. Once enough of them are there they'll have
| their own economy, and whoever owns them/the oxygen
| supply/whatever would be getting a lot of return. I don't
| think that's a great argument, though, for multiple
| reasons. I think it's better to just frame it as building
| a legacy. Put humans in an entirely new place that many
| of us desperately want to be, end up having the
| equivalent of a city named after you.
| kiba wrote:
| A dyson swarm is not a monolithic structure you build,
| but a civilization's collection of building.
| eep_social wrote:
| The ceiling on asteroid mining is orders of magnitude
| higher than anything constrained to earth. Put another
| way, imagine if you owned Australia because your company
| built it up off the ocean floor.
| helpfulContrib wrote:
| You're harnessing the entire energy output of a star. No need
| to transport anything - this is gathering, not hunting.
| tomtomistaken wrote:
| > this is gathering, not hunting.
|
| This metaphor doesn't make sense to me.
| quectophoton wrote:
| s/gathering/harvesting/, maybe?
|
| I'm guessing it's more like making a living space in the
| sphere itself or somewhere nearby and using the energy
| there (maybe exporting some percentage to Earth).
|
| Because if we're able to build the sphere itself, we
| probably would already know some way to cool it down in
| space so it doesn't burn itself, wasting all the money that
| went to its construction.
| e40 wrote:
| The disconnect is the dyson searm is in space and we're earth
| where we want to use the energy. How does it get to earth?
| throwaway11460 wrote:
| It doesn't, there's no need for planets at that time,
| people live on rotating artificial habitats that form the
| Dyson sphere itself.
| z3phyr wrote:
| > We are on earth
|
| No, if we have a dyson sphere, we are everywhere playa
| kibwen wrote:
| Fusion reactors will probably never be economical.
|
| It's the railgun problem: railguns let you trade complicated,
| unstable ammunition for cheap, stable slugs of metal. But the
| railgun imposes so much wear on its barrel, and the barrel
| itself is so much more expensive than in a traditional gun,
| that you've obliterated your cost savings.
|
| Likewise, it's irrelevant if fusion reactors can provide
| infinite energy from a single gram of hydrogen, because the
| reactor housing itself will be an impossibly complex machine
| with an extremely low lifespan from dealing with the energies
| involved.
|
| Is fusion possible? Probably. Will it ever be more economical
| than solar panels? Nope.
| vitiral wrote:
| Also: solar power is already a fusion generator
| lven wrote:
| I like the railgun analogy. I think you can stock up on other
| fusion cost arguments through my article, Engineering and
| Economic Challenges of Fusion:
| https://lvenneri.com/blog/ConFusion
| earthling8118 wrote:
| Solar panels would be nowhere near as effective far away from
| a star. Building things as far out as Jupiter or to traverse
| interstellar areas can't rely on them.
| Detrytus wrote:
| I know nothing about railguns, but if they are supposed to
| launch the projectiles with magnetic force then why do they
| need to impose any wear on its barrel at all? Couldn't you
| build a railgun where the projectile never even touches the
| barrel, being kept at the center by the same magnetic field
| that accelerates it? Or are we talking about the wear imposed
| by the magnetic field itself?
| andrewflnr wrote:
| If I recall correctly, a "railgun" per se is one that uses
| the projectile to conduct electricity between the "rails"
| that direct said projectile. So there's contact, between
| parts moving hypersonically relative to each other.
| jbotz wrote:
| > What am I missing?
|
| The scale.
|
| The reason to build a Dyson Sphere (or Swarm) is that you want
| all (or at least a large fraction) of the energy output of a
| star. To "build decentralized fusion reactors" that can provide
| the same scale of energy is even less practical than building a
| shell around a star and would require far more materials! Also,
| fusion is really simple when the ignition energy is provided
| for free by the gravitational compression of something the size
| of a star, and not so simple when you're trying to get it
| started on a small scale using any other form of energy for
| ignition. The bottom line is we don't really know if small-
| scale, controlled, net-energy-positive fusion is possible at
| all, but if it is it has a lot of overhead costs... you then
| have to deal with ignition energy, containment, etc. You're
| trying to make a mini-star and keep it tame. The physics are
| not favorable to this, they _are_ favorable to star-sized
| stars, where gravity and fusion energy pressure can balance
| each other for millions of years.
| ianburrell wrote:
| The concentrated energy of Dyson Sphere can be very useful.
| Feed some of it into lasers and then launch starships and
| then slow them down when they get to destination. Not tiny
| probes with fusion reactors but full size starships.
|
| Feed most of the energy of star to lasers and end up with
| weapon that will melt planets across the galaxy.
|
| Honestly, don't need to expand across the galaxy if have
| Dyson Sphere, which could be explanation of Fermi Paradox.
| VariableStar wrote:
| One aspect that I find problematic with the idea of Dyson spheres
| is: where will the energy be dissipated? In the civilization's
| planet's surface? It seems to me that it would create serious
| energy imbalances and soon climate disruption.
| cletus wrote:
| See my comment for a more detailed explanation but the short
| version is: a Dyson Swarm (preferred term) is merely a cloud of
| orbitals (ie not a rigid shell; there is no known or even
| theorized material with the strength to build a shell that
| large). The orbitals dissipate heat into space. That's what the
| infrared radiation is that they're looking for.
| VariableStar wrote:
| I see that. My point is that if the captured energy is used,
| and thus ultimately dissipated as heat, on the planet's
| surface, that planet is sooner than later going to have
| climatic imbalance.
| kiba wrote:
| Earth already do this. We only use some energy for our
| purpose.
| sdwr wrote:
| We are using the sun's energy that hits the earth. Some
| as light (which turns into heat), some as electricity
| (which turns into heat), and some as plant food > animal
| food > oil (which turns into heat)
|
| A Dyson sphere would capture the sun's energy that leaves
| the sun, not just the fraction that hits earth. Using
| that energy on earth would release far more heat than our
| current activities.
| kiba wrote:
| It would indeed be inadvisable to use all of sun energy
| captured on Earth, but they're not going to be used
| entirely on Earth.
| maxerickson wrote:
| The Earth radiates away solar energy, it's only here for
| a (figurative) moment.
|
| Human activities that convert other energy into heat
| don't particularly impact this process, the amount of
| energy from the sun is much larger.
| vitiral wrote:
| Planet? Dyson swarms orbit a SUN, not a planet
| fikama wrote:
| Its not where energy is sourced but wher its used. And
| assuming it will be civilisation's planet like Earth. The
| whole energy of the swarm will be used there. - It just
| has to increase temperature (due to additional energy on
| the planet)
| mcmoor wrote:
| There's Mathrioshka Brain
| https://en.m.wikipedia.org/wiki/Matrioshka_brain which
| uses the energy then and there for computation.
| TheLoafOfBread wrote:
| That actually makes no sense. You can't use (destroy)
| energy, you can only run it through processor, which will
| change it into heat while transistors inside are
| switching on/off. It is like a water wheel doing work by
| water flowing through it, but ultimately amount of water
| before and behind water wheel is same.
|
| Thus the question still stands, what happens to heat in
| such thing? Does it get recycled by some unknown device?
| Then it is closed system, you don't need input from
| outside. It won't get recycled? Then such device needs to
| get hot from dissipating that heat.
| vitiral wrote:
| Why would you use the energy on a planet? Clearly you
| would use the energy in space, probably in some of the
| same satellites that are gathering energy
| alchemist1e9 wrote:
| If they can build a sphere or swarm megastructure then
| obviously they would have build orbiting habitats either
| from scratch or terraforming planets or astroids.
| exe34 wrote:
| > The whole energy of the swarm will be used there
|
| that sounds like a made up problem. the Dyson swarm isn't
| to collect energy to send to the home planet. it's to
| collect energy. where that is used is going to be
| wherever it's needed. mining the asteroids, local
| computing (the cloud is no longer just a computer on
| earth, it's the cloud of the swarm elements), powering
| interstellar trips remotely, etc. the only thing that
| needs to get to earth is the imports of goods and
| services.
| cletus wrote:
| There are several possibilities here.
|
| First, the Earth already receives a ton of energy from the
| Sun that is "wasted". We estimate that at about 10^16 Watts
| of power, compared to humanity's energy usage, estimated at
| 10^10-10^11 watts. So Earth has a ton of energy
| dissipiation "built in" that we're not "using".
|
| Second, there is some inefficiency and thus heat
| dissipation in converting solar output into usable energy.
| Doing that in space means a bunch of heat dissipation
| happens in space rather than on your planet.
|
| Third, it's _relatively_ straightforwward to counter any
| increased heat dissipation on your planet by reducing that
| solar output that hits your planet. How? You build
| something at the EArth-Sun L1 Lagrange point. Reducing that
| solar output that hits the EArth by 1% would likely be
| unnoticeable to us but could cool the Earth significantly.
| Also, what do you build there? Well, lots of things. More
| orbitals, solar power collectors, etc.
|
| Fourth, how do you get power down to a planet? There are
| several candidates. One is to beam it down. This adds a
| conversion cost. But here's another: you build a n orbital
| ring [1] 100-150km above the EArth's surface. There are a
| ton of reasons you'd want to do this: interplanetary
| travel, cheap travel to and from LEO and easier travel
| across the planet (ie up to the ring, down to another point
| on Earth on cable cars, basically). But consider this: it
| gives you a rigid structure to attach solar power
| collectors to and you can run power transmission cables
| down from the ring to the planet's surface.
|
| [1]: https://www.youtube.com/watch?v=LMbI6sk-62E
| ericd wrote:
| I wonder how much reaction mass we'd need every year to
| keep something stationed at a Lagrange point to block 1%
| of earth's light, for combatting global warming. 1% of
| earth's light would be a heck of a solar sail.
|
| Looks like 1% would be 13.3 watts per meter, cross
| section of earth yields ~5.4x10^14 watts. Assuming
| perfect reflective, multiplying by 2/c gives 3.6x10^6 N.
| So like half of the thrust of one of Saturn V's engines?
| So... a lot of reaction mass, or some really powerful ion
| engines and a ton of power. So maybe not the most
| practical idea.
| cletus wrote:
| It's true that the L1 Lagrange point is unstable so would
| need some station-keeping. It's an issue but it's a
| solvable issue. For one thying you have a bunch of energy
| to spend. For another, the solar wind itself can be used
| to provide momentum going out if what you have there is
| sufficiently light.
|
| But there's another option: statites [1]. Statites are
| solar power collectors that have an incredibly thin sail
| to the point that they don't need to orbit the Sun at
| all. This means you have a bunch more options for
| positioning. Clearly the Earth will continue to revolve
| around the Sun but a sufficient swarm of statites on the
| EArth's orbital plane could have the same net effect as,
| say, driving beneath a bunch of stationary umbrellas.
|
| Or statites can themselves do station-keeping at L1. They
| can angle themselves to provide momentum in a bunch of
| directions. Or they can orbit the L1 point similar to how
| JWST orbits L2. Their ability to use the solar wind for
| directional momentum could satisfy station keeping needs.
|
| [1]: https://en.wikipedia.org/wiki/Statite
| kobalsky wrote:
| if a civilization needs so much power they build a dyson
| sphere they probably have terraforming nailed.
|
| that kind of technology probably takes hundred of thousands
| of years of technological development and we have had
| electricity for how long?
| Karellen wrote:
| One solution to this is the Matrioshka brain, which consists of
| many nested "shells" around the star. Each one absorbs the
| radiation from the hotter shell inside it (or from the star, if
| the inner shell), and radiates waste heat to the cooler shell
| outside it. The temperature differential between the inside and
| outside of each shell is what allows work to be done. The outer
| surface of the outermost shell, maybe 5 billion km (~35AU, or a
| bit further out than Neptune) from the star, will be close to
| the ambient temperature of the interstellar medium, and will
| radiate heat at only a few Kelvin into it.
|
| https://en.wikipedia.org/wiki/Matrioshka_brain
| micw wrote:
| So instead of seing a hot "small" spot (the star), we'd see a
| warm (a bit above absolute zero) but very large sphere?
| javcasas wrote:
| Well, seeing it may be an exaggeration. It would be barely
| less black than the space around it. Though it may shadow
| other stars and distant objects.
| kjkjadksj wrote:
| My assumption is if you demand the energy needs of a dyson
| swarm you've probably figured out how to convert this energy to
| work with none of it lost to heat.
| TheLoafOfBread wrote:
| Then why would you need a Dyson swarm at a first place, when
| you can just recycle heat energy through your systems with
| almost 100% efficiency?
| greenthrow wrote:
| Looking for Dyson Spheres or "the Simulation" or any other highly
| speculative technology is anti-science. It is the opposite of
| evidence based. I am so sick of these non-science ideas being
| promulgated and given resources when there is plenty of actual
| science (evidence based) that needs funding.
| kiba wrote:
| Dyson sphere(swarm, because sphere is misconstrued as solid) is
| based entirely on known physics and can be made with our
| existing technology base, just not with our current industrial
| base.
|
| SETI is a valid research priority.
| greenthrow wrote:
| Unicorns are made entirely with known biology. That doesn't
| mean funding a search for them is a good use of resources.
|
| SETI is a valid research priority. There's plenty of less
| speculative signs we can look for.
| vitiral wrote:
| I do not want to be living in your head. Why is searching the
| unknown with the tools at our disposal anti-science? Because it
| goes against some kind of norm held by what is deemed the
| "scientific community"? Who even is that and why do they get to
| say what knowledge to pursue?
| greenthrow wrote:
| I already explained. Evidence. Looking for the unknown does
| not necessitate looking for a specific highly speculative
| technology that there is zero evidence for and zero reason to
| believe exists other than it's a cool idea.
| kiba wrote:
| It is not really a speculative technology. A Dyson Swarm is
| doable within our existing technological base. If we are
| capable of building an artificial satellite, we can build a
| dyson swarm.
| greenthrow wrote:
| Baloney. We can not build one that is of any use. That is
| the speculative part of it. Inherent in looking for it is
| that it's an extremely worthwhile, nearly inevitable,
| idea. We have zero evidence for that.
| kiba wrote:
| We build satellites that look at our sun. That's one part
| of our dyson swarm. The beauty about a dyson swarm is
| that it can be built incrementally over time as we find
| new uses for space.
| motoboi wrote:
| Science need theories. Theories can be used to look at the
| world in search of evidence.
|
| We have two nice theories here. People just doing the search
| now.
| greenthrow wrote:
| Theories that are worth investigating should be based on past
| evidence. They should be attempts to explain things we have
| observed. If they aren't they are wild speculation, and as I
| said, anti-science.
| motoboi wrote:
| Donald Knuth would love to have a talk with you about the
| need for theories as basis for scientific inquiry, not the
| opposite.
| timschmidt wrote:
| Please see this video: "Science Needs Pseudoscience to
| Advance": https://www.youtube.com/watch?v=VQ-031A4G1Y
| quectophoton wrote:
| [adjusts glasses] Ackshually, the article seems to be more a
| hypothesis than a theory.
|
| But yes, jokes aside, hypotheses are also needed for science.
| PurpleRamen wrote:
| Science is a process, not a religion. And speculating, building
| reasoning and models, which you then try to verify, is the core
| of science.
| analog31 wrote:
| Ironically, if someone were to say "this is not science" in a
| thread about dark matter or string theory, they'd be upvoted.
|
| My own take is that it's not science, but engineering, in the
| sense that it's based on already established scientific
| principles. It's more like a project proposal. The unknown is
| not whether it's physically possible, but whether we can find a
| civilization that has built one.
| elorant wrote:
| To me, Dyson Spheres seem impractical. For one, where are you
| going to find all the material needed to cover even a fraction of
| the surface of a star? Additionally, if you do build something
| that massive, you'll probably influence the movement of the
| planets.
| _dain_ wrote:
| You disassemble a planet for the raw materials. Mercury would
| do.
|
| The real problem is that Dyson spheres are wasteful because
| stellar fusion is thermodynamically inefficient. If you harvest
| the material of the star and fuse it yourself, you can keep the
| lights on for trillions of years.
| aurareturn wrote:
| The OP's second point is that you would change the
| gravitational balance of the solar system if you disassemble
| mercury.
| mattsan wrote:
| Funny thought - want to solve global warming? Disassemble
| Mercury! Earth's orbit in theory would space a bit further
| out
| aurareturn wrote:
| Ever heard of the 3 body problem? No way we can reliably
| model that.
| mattsan wrote:
| Was a joke :)
| blamestross wrote:
| So that isn't true. The 3 body problem is a problem in
| theory and extreme situations, not practice.
|
| We discovered half the planets by doing the math to
| predict the orbits based on the known distribution of
| math in the solar system.
|
| General Relativity was initially validated by predicting
| mercury's orbit accurately.
| vitiral wrote:
| 3 body problem: orbital decay when there are three
| orbiting bodies of SIMILAR MASS.
|
| Mercury is not similar mass to the sun, so this is not
| the three body problem
| prettyStandard wrote:
| Okay but if you kept all that mass inside of Earth's
| orbit then you would not change the center of gravity,
| and Earth's orbit wouldn't change.
| elorant wrote:
| Sure, and what happens next with the trajectories of the
| remaining planets?
| _dain_ wrote:
| They'd be perturbed a little but it's not like they'd go
| colliding into anything. It's not a big deal; shell theorem
| applies.
| mr_mitm wrote:
| Interesting thought. I've never heard of this idea. Let's
| think it through.
|
| If I understood correctly, you suggest to turn the heat from
| fusion into a usable form of energy. On earth we'd do that
| using steam turbines. Harvesting only the hydrogen from the
| star to bring it on a planet and fuse it in a reactor seems
| silly, as the hydrogen is already at sufficient temperature
| to fuse on its own. So we could send water and steam turbines
| close to the sun where the turbines charge some sort of
| battery? Perhaps on some super elliptic orbit, where we
| switch the full batteries with empty batteries at the
| apihelion.
|
| Or did you have something else in mind?
| vincnetas wrote:
| it can be super thin (compared to sun scale) so you wont need
| lots of material, like you dont need lots of gold to plate
| contacts. And as there is not a lot of mass there will be not a
| lot of influence on gravitational field.
| hawski wrote:
| I don't want to say they are practical, but for sure you would
| build them with planetary matter so you would influence the
| movement of planets as you would dismantle them. At the end you
| would not have any planets left.
| quectophoton wrote:
| My question when it comes to Dyson Spheres is, how does one get
| the sphere to _stay there_?
|
| In contrast, a Dyson Swarm is easier for my uneducated mind to
| understand.
| throwaway11460 wrote:
| I don't think the article and researchers meant it's actual
| rigid sphere, that's just the Star Trek based popular
| opinion. Dyson Sphere is Dyson Swarm, people just didn't get
| it the first time.
| throwaway11460 wrote:
| You dismantle the planets to build Bishop Rings and
| O'Neill/McKendree cylinders which form your Dyson Sphere/Swarm.
| A_D_E_P_T wrote:
| Interestingly, all of those supposed spheres are around dwarf
| stars, which make them inherently more practical for two
| reasons:
|
| 1) Much less material required
|
| 2) Much longer star lifespan (trillions of years rather than a
| handful of billions)
|
| However, what's interesting is that those spheres all seem to
| be around red dwarf stars, which are much more active and
| shorter-lived than white dwarfs. They're just not as stable.
|
| Our nearest neighbor, Proxima Centauri, is a violently active
| flare star -- and it's also a red dwarf with an estimated
| lifespan of ~4 trillion years.
| ChrisMarshallNY wrote:
| _> red dwarf stars, which are much more active and shorter-
| lived than white dwarfs. _
|
| I was under the impression that red dwarfs are the longest-
| lived stars.
| A_D_E_P_T wrote:
| On the main sequence, yeah.
|
| But white dwarfs -- which are technically stellar remnants
| -- are indefinitely stable. They just keep cooling. It's
| surmised that they'll still be quite a lot warmer than the
| universe's background temperature in 10^15 years.
|
| This has yet to be observed, but red dwarf stars, when they
| reach the end of their lifespan, should contract and become
| white dwarfs. It's said that our sun will also eventually
| end up as a white dwarf.
|
| White dwarfs are superlatively stable, long-lived, and
| quite hot. And there are already quite a lot of them. If
| you're going to build a Dyson sphere/swarm, they're a very
| good choice. Though red dwarfs aren't bad...
| PurpleRamen wrote:
| If you are on the level to think about building a Dyson sphere,
| you are probably also able to create solid matter from the
| star's energy itself and the other matter floating around the
| star system. At that point, it's more a question of how long it
| takes, then how you do it.
| cletus wrote:
| The term "Dyson Swarm" is preferred because it is a cloud of
| orbitals, not a rigid sphere. A rigid sphere was never the idea
| proposed (by Freeman Dyson). This idea comes from science
| fiction misunderstandings of the term "Sphere".
|
| Think of a Dyson Swarm ("Sphere") as the water droplets in a
| fog. Collectively they absorb the light going through but the
| water droplets (and the orbitals) are relatively sparse. So a
| billion orbitals around our Sun at a distance Venus and Mars
| would still have a mean distance between them of over
| 100,000km.
|
| So how much material do you need? One estimate I've seen for a
| billion such orbitals is less than 1% of the mass of Mercury.
| Why Mercury? Because it's metal-rich and its proximity to the
| Sun means energy is incredibly abundant and cheap.
|
| That's to build _billions_ of O 'Neil Cylinders.
|
| Even if you don't need that much living room, here's something
| else you can build: statites. That's a portmanteau of "static
| satellite". Instead of orbiting the star, they are so light
| that the solar wind is sufficient to counterbalance the
| gravity. These things would simply collect energy and/or just
| reduce the amount of solar energy hitting something like a
| planet (eg to cool the EArth).
| consumer451 wrote:
| Just an hour ago, I learned about Przybylski's Star. [0]
|
| > Przybylski's observations indicated unusually low amounts of
| iron and nickel in the star's spectrum, but higher amounts of
| unusual elements such as strontium, holmium, niobium, scandium,
| yttrium, caesium, neodymium, praseodymium, thorium, ytterbium,
| and uranium.
|
| While the explanation is likely some unknown natural process,
| salting a star with an impossible chemical composition might also
| be a way for a technological species to create a monument,
| correct? This seems like it would involve moving less mass around
| than a Dyson Sphere/Swarm, although it would need a constant
| feed, if I understand the situation correctly.
|
| Astonishingly, there appears to be no contemporary analysis of
| this star.
|
| [0] https://en.wikipedia.org/wiki/Przybylski%27s_Star
|
| "The Star That Shouldn't Exist" - Prof. David Kipping
|
| https://www.youtube.com/watch?v=maMDGZOD3mI
|
| "Why is There Plutonium in This Star? Przybylski's Star with
| David Kipping" - Event Horizon
|
| https://www.youtube.com/watch?v=VUbjdaPy4mw
| consumer451 wrote:
| > Astonishingly, there appears to be no contemporary analysis
| of this star.
|
| I should have stated: there appear to be no contemporary
| _observations_ of this star.
|
| Also, one of the more interesting things to me is that
| ytterbium, for example, has a half-life which is measured in
| days.
| consp wrote:
| > Also, one of the more interesting things to me is that
| ytterbium, for example, has a half-life which is measured in
| days.
|
| Which ytterbium are you talking about? It has 7
| observationally stable isotopes[1].
|
| [1] https://en.wikipedia.org/wiki/Isotopes_of_ytterbium
| consumer451 wrote:
| Yeah, you are correct. My brain is a bad model lately,
| since Advanced Neuro Lyme Disease. I synthesized the
| information from those podcasts + google poorly. This is
| depressing.
| consp wrote:
| There are plenty of possible signatures (though
| uncertain) of actinides in there as well, some of those
| -could- have short lifetimes so not that far off.
| consumer451 wrote:
| Thanks, but I should have caught that. The good news is
| now that my brain is not as good at the details [0], I
| may finally be a good fit for a management role (:
|
| [0] It's actually getting a lot better, I hit brain-rock-
| bottom a year ago. I literally could not think at all.
| Damn those ticks.
| bcherny wrote:
| Also see Greg Egan's Diaspora, really great sci-fi that
| explores this idea.
| api wrote:
| Maybe instead of a cosmic scale nuclear waste stir fry there's
| something orbiting or around that star making its spectrum look
| funny.
|
| Of course that's just as sus if not more.
|
| Aim JWST at that thing.
| walkabilitee wrote:
| One could also imagine a huge rotating, sun-orbiting ring with
| alternating openings that blinks a out message to astronomical
| observers, perhaps in some form of Morse code or binary.
| consumer451 wrote:
| This is what I always used to imagine as our monument, maybe
| the Fibonacci sequence via orbiting star shades. Or maybe
| that's too natural, maybe a binary sequence via orbiting star
| shades.
|
| However, while I ain't no city-slickin' Kardashev Type II
| orbital mechanic, all those star shades might not be in a
| stable orbit over hundreds of millions of years. They might
| require some propulsion for station keeping. That sounds hard
| for anyone, across those time scales. Especially as the star
| grows.
|
| It might be "easier" for longevity, to terraform a Mercury
| type planet with unnatural chemicals, then smash a large off-
| plane comet into it, to create a band of non-star weird
| chemicals which would fall into the star and should last for
| millions of years, giving it a one-in-a-billion spectrograph?
| BurningFrog wrote:
| I'm amused by all the "but the Dyson Sphere might affect the
| natural environment" comments.
|
| Building a Dyson Sphere is 100% incompatible with Sierra Club
| philosophy!
|
| It is about ruthlessly destroying the natural world and replacing
| it with something you prefer. At maximum scale!
| prepend wrote:
| Its important to only purchase organic Dyson spheres.
| dmd wrote:
| When I was 10 (1988) reading Larry Niven's "Integral Trees" I
| was disappointed that the story didn't end - as I had
| expected it to - with the Carther descendants eventually
| _building_ trees to entirely surround the star.
| mglz wrote:
| If you can build a Dyson sphere it should be trivial to
| maintain a few extra planets worth of natural environment, or
| even life seed some new worlds.
| lven wrote:
| nah you can just create little holes in the sphere to
| illuminate the planets. negligible power loss. Earth and all
| the planets live on the sun's crumbs, no the (crumbs of the
| cumbs)^12
| micw wrote:
| Good point. Since all our planets surround the sun more or
| less in the same plane, the dyson sphere could cover the
| remaining 95% of the sphere without affecting the planets too
| much. Remains the issue that you'd probably need the material
| of those planets to build the dyson sphere.
| deadbabe wrote:
| I'm less intrigued by the Dyson sphere than I am about what a
| civilization would actually _do_ with all that power? Create tiny
| worm holes?
| z3phyr wrote:
| Sure, create worm holes, travel dimensions and all that
| deadbabe wrote:
| Isn't it kinda dangerous to observe a civilization that has
| figured out how to know it has been observed and then
| instantly wormhole their way to us?
| z3phyr wrote:
| I mean, Its dangerous to exist in the same space as a
| potentially advanced aliens. Might as well observe them.
| mr_mitm wrote:
| You cannot create wormholes instantly, their creation is
| still bound by the speed of light.
|
| Also, the energy requirements for wormholes are well above
| of what one measly star can provide, not to speak of a host
| of other issues.
| cletus wrote:
| Three big possibilities:
|
| 1. Interstellar travel: people don't realize just how large the
| energy budgets are to get to even the nearest stars, even with
| pure matter-to-energy conversion. This is, of course, the
| theoretical upper limit of efficiency but we have nothing
| remotely close to it. Chemical rockets are complete nonstarter
| becasue of the mass of the fuel makes the entire thing
| nonviable, even in a theoretical sense, beyond a travel time of
| hundreds of thousands of years. Even then you need energy to
| survive so it's unclear if you have enough.
|
| So what do you do? Well, if you can reach interstellar speeds
| without using fuel you've solved so many problems. How do you
| do that? You focus energy from the Sun onto effectively a solar
| sail. You still need to slow down at the other end but you get
| some of this for "free" with resistance from the interstellar
| medium.
|
| 2. Computers. Our ability to utilize extra computing power
| shouldn't be underestimated. One possibility is virtual worlds.
| One estimate I've seen is that you need about 10^15
| operations/second to simulate a human brain. A Matrioshka Brain
| (basically a Dyson Swarm that's essentially a giant computer)
| gets to (IIRC) ~10^80 operations/second. AIs that are basically
| people could live an entire virtual existence.
|
| 3. Weapons. Basically, if you have a Dyson Swarm you could
| sterilize the galaxy in about 100,000 years if you wanted to
| with a so-called Nicoll-Dyson Beam. Or use relativistic kill
| missiles taht are just basically lumps of metal or rock at near
| light speed.
| deadbabe wrote:
| If human brains are proof you don't need the energy of a star
| to do 10^15 operations/second, doesn't that just mean our
| understanding of how to build efficient computers is very
| primitive?
| benhurmarcel wrote:
| If we look at what we use it for, it would probably to power
| some kind of cryptocurrency speculation scheme, or personal AI
| generation of ads for neural implants.
| dghughes wrote:
| Imagine if a Type II civilization built a Dyson sphere around a
| star but a Type I civilization was on a nearby planet. Then again
| I guess at that point the Type I and III would be aware of each
| other. I wonder could the Type I planet stop the Type III
| civilization? The Type III would be like gods to the Type I's but
| the Type I's would be nothing more than a nuisance if even that
| to the Type IIIs.
| m3kw9 wrote:
| Dyson Sphere seem like what we would do based on our
| understanding of physics would do, and of course how else would
| you theorize such device? My theory is that an advanced
| civilization would not need to brute force such methods and use
| novel physics to gather energy, fusion is a start but there has
| to be even more advanced methods.
| rthnbgrredf wrote:
| The current total world-wide production of anti-protons in a
| period of a year is in the range of nanograms. Maybe we will
| never see a dyson sphere because all far advanced civilisations
| have antimatter reactors.
| micw wrote:
| I wonder if the material of all the stuff in our sun's orbit
| would be sufficient to build a dyson sphere. Afaik, 99% of the
| mass of our solar system is the sun itself...
| andsoitis wrote:
| Which begs the question, how do you obtain sufficient energy to
| go scouting for material beyond the solar system in order to
| construct something that encircles the sun...
| baq wrote:
| You figure out how to put a fusion reactor on a spaceship
| without melting the whole thing into a blob of metal and use
| a particle accelerator as a super high isp engine.
|
| Sci-fi but mostly in the 'not melting down' part.
| cletus wrote:
| To build about a billion O'Neil Cylinders, which is about the
| number you'd need for a full Dyson Swarm around our Sun, would
| consume (IIRC) 1% of Mercury's mass.
| mistercow wrote:
| I don't think proportion of mass is relevant here. An apple
| peel is maybe 3% of the mass of an apple, and a Dyson sphere
| would be a proportionally much thinner "skin" around a star
| than an apple peel.
| TheLoafOfBread wrote:
| Whole concept of Dyson sphere/swarm is anachronistic. It is like
| trying to build the Internet based on carrying pigeons, while you
| have available fiber optics and advanced radio communication.
| Because the moment you have enough technological advancements to
| build and deploy such a thing, you can already build fusion
| reactors by million units a year and maybe you already have even
| better ways how to manage energy. In the end the matter itself is
| just a different form of energy.
| javcasas wrote:
| The sun burns around 600 million tons of hydrogen per second
| https://cosmicopia.gsfc.nasa.gov/qa_sun.html I don't think you
| building a million new fusion reactors per year so that each of
| them burns maybe 100kg of hydrogen per year even starts to be
| comparable in a few thousand years.
|
| The energy emitted by the sun is just several orders of
| magnitude beyond what you can source from a planet. It's just
| that huge.
| TheLoafOfBread wrote:
| But I can carry such reactor into Oort cloud and beyond. I
| can power my ship in a shadow of a planet or asteroid and
| most importantly I am not dependent on one megastructure,
| which can fail, be destroyed or taken over by hostile forces.
| floxy wrote:
| ?Por que no los dos?
| javcasas wrote:
| The dyson sphere can power a huge factory, capable of
| making thousands if not millions of warships per second. It
| can also power a star-sized laser capable of vaporizing
| pretty much any incoming army, or even bigger objects like
| small planets. Your dyson sphere will be safe to everything
| but civilizations capable of playing marbles with stars and
| black holes.
|
| Also you can use your star-sized factory to make starships
| with fusion reactors. Not a problem.
| TheLoafOfBread wrote:
| But if you want to get beyond Jupiter, then whole Dyson
| swarm is useless to you, because you don't have source of
| energy. And again when somebody will get control over
| such swarm, then such person has control over whole
| civilization around that star which was foolish enough to
| build it and rely on it at a first place.
| javcasas wrote:
| What stops you from using a bit of the sun's output that
| you are capturing to materialize a starship with it's own
| reactor and thrusters, and then open a window in the
| sphere to let that ship leave?
|
| I mean, it looks like you want to _contain_ all the
| energy of a sun for the sake of containing it, not to do
| cool stuff with it.
| cletus wrote:
| That's a very optimistic view of the future of fusion, IMHO an
| unreasonably naive view. There are lots of problems with fusion
| that are unclear if they will _ever_ be solved, specifically:
|
| 1. Energy loss from neutron escape. Stars don't have this issue
| because they are incredibly large (so your neutron will hit
| something else more likely than not) and gravity;
|
| 2. Vessel destruction from lost neutrons (ie neutron
| embrittlement);
|
| 3. Assuming D-T fusion, you're producing helium atoms. Helium
| is a pesky substance. It's chemically neutral and a helium atom
| is (AFAIK) the smallest atom, even smaller than a hydrogen
| atom. That means it is hard to contain and also has a tendency
| to damage your container;
|
| 4. Fusion reactors are, in a way, somewhat primitive. Why?
| Because ultimately you generate heat and turn a turbine like we
| do in every coal and natural gas plant. Moving parts are bad.
|
| 5. Fuel. Depending on what fuel you need, this is somewhere
| between a small problem (eg protium or even deuterium) to a
| hassle (eg tritium) to a major problem (eg He-3).
|
| 6. Waste. This depends on fuel somewhat eg do you need to use
| fissile materials to create Tritium?
|
| Much more detail [1].
|
| We obviously don't know the economics of fusion yet because it
| doesn't exist, but the economics of nuclear fission are, well,
| terrible (in both capex and opex terms).
|
| Once you put a solar panel in space, it produces ~7 times the
| power. There's no loss to cloud cover, getting covered in
| dust/dirt, atmosphereic loss and the day/night cycle.
|
| For an orbital, you simply cover the exterior with solar panels
| and you're done for power generation. No moving parts, no
| catastrophic failure modes (eg meltdowns in nuclear plants),
| it's scalable and when panels break down you simply remove them
| and plug in a new one.
|
| I expect other forms of power generation will find a niche use
| far from the Sun in the same way that submarines have different
| operating characteristics to a suburb. But I'm skeptical fusion
| will ever be the preferred method of power generation.
|
| [1]: https://thebulletin.org/2017/04/fusion-reactors-not-what-
| the...
| TheLoafOfBread wrote:
| Dyson swarm has some naive approaches too
|
| 1. You don't have a way how to transfer power from Dyson
| swarm without absurdly staggering losses.
|
| 2. Dyson swarm satellite would be heated up by incoming heat
| from Sun on one side and heated up by whatever mean you want
| to transfer that energy on the other side and unable to cool
| itself down because it is in vacuum of space. So even that
| power on the paper is eye popping, actual power would be
| fraction of a fraction of nameplate power because then you
| would overheated and destroy it. And now question would be,
| is such constrained satellite able to make more energy than
| it was invested into making of this satellite?
|
| Combine 1 and 2 together and real output from such structure
| would be close to zero.
| cletus wrote:
| > You don't have a way how to transfer power from Dyson
| swarm without absurdly staggering losses.
|
| Why do you need to transfer power? The point of an orbital
| is primarily for people to live on. A single orbital could
| potentially support a million or more people.
|
| Are you referring to the issue of providing power to Earth?
| That's... a separate issue, with different solutions. The
| idea of power satellites [1] has had a lot of thought. An
| alternative approach is to build an orbital ring [2] and
| hang solar power collectors off of it. You could this power
| directly to the ground with transmission lines.
|
| > Dyson swarm satellite would be heated up by incoming heat
| from Sun on one side
|
| An orbital would be heated on the side facing the Sun and
| radiate away heat away when not facing the Sun in the exact
| same way that the Moon is scorching hot when facing the Sun
| and 200 below zero when not.
|
| [1]: https://www.youtube.com/watch?v=eBCbdThIJNE
|
| [2]: https://www.youtube.com/watch?v=LMbI6sk-62E
| TheLoafOfBread wrote:
| You are misunderstanding my question. I am talking about
| Dyson swarm satellite, not about habitat with solar
| panels.
| Zigurd wrote:
| Not that I think speculation is bad, but the concept of
| intelligences expanding by building space structures so immense
| needs some push-back:
|
| Is there enough time in the lifetime of a star to build and use
| those structures?
|
| Are there plausible social arrangements stable enough to last the
| duration of such a project?
|
| Are there intelligent beings with a drive to limitlessly expand
| their population?
|
| A lot of the ideas behind hypothesizing swarms of space
| structures, each orders of magnitude more massive than Earth,
| feels very 1970s population/energy-crisis inspired.
| sockaddr wrote:
| > Is there enough time in the lifetime of a star to build and
| use those structures?
|
| If a brown dwarf, most certainly
|
| > Are there plausible social arrangements stable enough to last
| the duration of such a project?
|
| Could just be an unterminated machine process initiated by
| living beings at some point
|
| > Are there intelligent beings with a drive to limitlessly
| expand their population?
|
| This one, I agree. I think once we start expending enough we'll
| realize there's only so much that extra matter and energy will
| get you and it doesn't bring you closer to "solving" the
| universe or escaping it and you just stop going for more.
| cletus wrote:
| > Is there enough time in the lifetime of a star to build and
| use those structures?
|
| Easily. Sci-fi has misconstrued what a Dyson Sphere is to the
| point where the preferred nomenclature is "Dyson Swarm". A
| Dyson Sphere was never a rigid shell around a star. Such a
| thing isn't possible with any known or theorized material. And
| it makes no sense even if you could.
|
| So a Dyson Swarm around our Sun would be approximately a
| billion O'Neil Cylinders (orbitals 2-4 miles in diameter and
| 10-20 miles long). You don't have to build them all at once.
| Build them as you need them. The more you build the more
| industrial capacity you have. They can all be built
| independently too.
|
| I imagine it would take less than 10 years to build one once
| you have the capability.
|
| > Are there intelligent beings with a drive to limitlessly
| expand their population?
|
| Population is only one concern. A more driving force may well
| be the desire for energy and raw materials. Raw materials, and
| in fact most problems, can be reduced to being an energy
| problem. Some things will require a truly mind-boggling amount
| of energy eg interstellar travel.
|
| Our Sun won't live forever. It's estimated to go into a red
| giant phase in 4-5 billion years, that will end up swallowing
| the Earth most likely. Long before then, life won't be able to
| exist on Earth as the Sun's solar output is increasing by about
| 10% every billion years. Earth as it stands now to us as we are
| now will be uninhabitable in ~1.6 billion years.
|
| So to be truly long-lived we're going to have to do something
| about that. There are lots of options. Those include reducing
| the energy that hits the Earth, moving the Earth or moving our
| species to a different system. The last one is particularly
| attractive because white or red dwarves will likely exist for
| trillions of years. Every one of these options requires a vast
| amount of energy.
|
| > ... swarms of space structures, each orders of magnitude more
| massive than Earth
|
| That's not what a Dyswon Swarm is.
| api wrote:
| > Are there intelligent beings with a drive to limitlessly
| expand their population?
|
| Since the development of contraceptives we are now selecting
| _hard_ for any and all traits associated with intentional
| reproduction or the desire for children.
|
| A few thousand years of this and the only thing left will be
| people who really want kids, or who are prone to adopt
| beliefs or attitudes that lead them to want kids.
|
| Maybe this is how you get a Dyson swarm.
|
| I'm not even including potential AI "life" in this picture.
| Zigurd wrote:
| When you give women literacy, opportunity, and bodily
| autonomy, population problems go away.
| api wrote:
| ... for now.
|
| What happens after ten generations of selection for the
| ones who reproduced?
|
| (This is also a major reason I think the current right
| wing fertility panic is mostly bullshit with the
| exception of maybe a few places with unusually low rates
| of reproduction.)
| marcosdumay wrote:
| > Is there enough time in the lifetime of a star to build and
| use those structures?
|
| It's built in centuries, a star lived for billions of years (a
| few live for only hundreds of millions, but that's still
| enough).
|
| Your other questions assume literal aliens would behave on the
| exact way you expect them to. That's not a sane assumption.
| NoMoreNicksLeft wrote:
| > Are there intelligent beings with a drive to limitlessly
| expand their population?
|
| Let's assume a few things. They're biological (for what passes
| as biology on their planet, anyway), and evolved from what were
| originally single-celled organisms. They didn't blink into
| existence as Boltzman Brains or something like that. Also, they
| are a group of individual beings, and it wasn't some sort of
| global hivemind with a singular being surrounding the entire
| planet like some coral or whatever.
|
| If these assumptions are valid, then yes, they'll have a drive
| to limitlessly expand their population, because those species
| that didn't have this drive became extinct in their prehistory.
| They'll be puzzled by it, might go through a phase where it
| causes them the equivalent of shame, then they'll grow past
| that and not care once again. And they'll expand. Because not
| expanding risks extinction, just like it does with us. We
| either expand to multiple locations outside of our planet, or
| we risk extinction.
|
| > Are there plausible social arrangements stable enough to last
| the duration of such a project?
|
| Maybe not. Who cares. If in the 20th century we became aware of
| a human Dyson spehere half-built in our solar system, a million
| years old and unfinished, you think we wouldn't turn around and
| start finishing it? Social arrangements may be unstable and
| cause minor disruptions, but so too are minor disruptions
| unstable and humanity might return to the norm on timescales
| relevant to the construction of a Dyson sphere.
|
| > Is there enough time in the lifetime of a star to build and
| use those structures?
|
| This is a good question. I don't know the answer to it. We've
| got, what, another billion years or two in ours? If the
| construction only takes a couple million years, seems like it
| might be worth it. Though the thought of the cost overruns and
| so forth should make even the mightiest bureaucrat shrink in
| terror.
|
| > A lot of the ideas behind hypothesizing swarms of space
| structures, each orders of magnitude more massive than Earth,
| feels very 1970s population/energy-crisis inspired.
|
| I find this hilarious in ways that I can't put into the words
| to share with you just how funny it is.
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