[HN Gopher] Upper limits on partial Dyson spheres in the Milky Way
___________________________________________________________________
Upper limits on partial Dyson spheres in the Milky Way
Author : perihelions
Score : 133 points
Date : 2022-02-19 05:16 UTC (17 hours ago)
(HTM) web link (arxiv.org)
(TXT) w3m dump (arxiv.org)
| nyx wrote:
| Most people get baked, wonder if we're alone in the universe, and
| take a nap. Astrophysicists get baked, wonder if we're alone in
| the universe, and publish papers like this.
|
| Jokes aside, is there really any practical value in this sort of
| research, or is it the kind of thing that we do because it's
| interesting and kinda cool? Don't get me wrong, I think it's
| valuable for that alone, but...
| captainmuon wrote:
| Searching for Dyson spheres is not too different from searching
| for other hypothetical astronomical objects. Maybe it is a low-
| stakes analysis you could put some students on, so they learn
| something. Data collection, statistical methods, paper writing
| is all identical to "traditional" searches. I come from
| particle physics, and we did quite a few searches for very
| weird particles that, I admit, didn't believe in. But it was
| quick to retool the search for more plausible models.
|
| Also I think science works the way that you use your fantasy to
| come up with outlandish things, and then try to rule them out
| with logic.
| dillondoyle wrote:
| How do you find one? Is it similar to a black hole where you
| can detect the gravity, but can't see any of the energy
| coming from the covered sun?
| terramex wrote:
| Dyson sphere would emit significant amount of infrared
| light but no visible light. Original Freeman Dyson's paper
| from 1960 was titled "Search for Artificial Stellar Sources
| of Infrared Radiation" https://sci-
| hub.ee/10.1126/science.131.3414.1667
| ncmncm wrote:
| When somebody got a telescope that could, they found
| there were way more sources of infrared radiation than
| visible stars.
| JuettnerDistrib wrote:
| > is there really any practical value in this sort of research
|
| In many ways it is too early to do this research, so it is a
| kind of art (as is a lot of research, imho). As long as only a
| few people do it, it's cool and useful so we can be aware of
| our potential future.
|
| On the other hand, since we have no credible evidence of
| extraterrestrials, it would be surprising to find a
| civilisation so advanced to build a Dyson sphere. If they can
| build Dyson spheres, wouldn't they already be all over the
| place?
|
| Ok, I suppose I should actually go read the paper now...
| bryanrasmussen wrote:
| Being able to build Dyson spheres does not make them capable
| of going faster than the speed of light, so any civilization
| capable of building a Dyson sphere would probably still be
| clustered around a couple stars and that's it.
|
| Would such a civilization spread to more than one star is
| actually also a question, or would they control their
| population rationally stay on their Dyson sphere and only
| start to move when the star had less than 100,000 years left
| to go.
|
| Only some Dyson sphere variants, like Shkadov thrusters, are
| primarily conceived as ways to move around. Which personally
| seems to me less likely, is a civilization, as well as the
| ability to construct these objects, also going to have a
| species level interest in going exploring?
| perihelions wrote:
| > _" Being able to build Dyson spheres does not make them
| capable of going faster than the speed of light, so any
| civilization capable of building a Dyson sphere would
| probably still be clustered around a couple stars and
| that's it."_
|
| Check your math: this galaxy is ~10^5 light-years in size
| and ~10^10 years in age.
| bryanrasmussen wrote:
| what does that have to do with anything I said? Yes, I
| guess they would be everywhere if their civilization was
| able to make Dyson spheres 1 year after the creation of
| the galaxy, also if they decided to
|
| 1. Not control their population for some reason.
|
| 2. Had some sort of interest in exploring.
|
| 3. Implicit also in the speed of light thing, would find
| it really interesting to send a portion of their
| population to the next available and suitable star which
| might be enough light years away to make communication
| impractical. I mean for our civilization there is some
| level of argument that says it would be a ridiculous idea
| to move to a new solar system and we have an intellectual
| exploratory streak in our species.
|
| I mean we are currently not at the level of being able to
| do a Dyson sphere, it took us 4.543 billion years (age of
| earth) to get to the part that somebody could conceive of
| it. There is also some discussion as to whether or not
| our civilization is going to last, so given that and the
| other things I said it seems unlikely to me that any
| Dyson sphere civilization would actually build more than
| one, but maybe some build two because binary stars or
| some other weird circumstance which makes it worthwhile
| to do.
|
| on edit: if we get to Dyson sphere building capabilities
| which seems really unlikely, will we build more than one?
| How many more?
| MattPalmer1086 wrote:
| The point is that you don't need to go faster than the
| speed of light. There's more than enough time to cover
| the entire galaxy in a relatively short period of time at
| sublight speeds. A few million years is sufficient.
| bryanrasmussen wrote:
| yeah, sure, enough time to GO everywhere but not enough
| time to BE everywhere, which is a different thing
| entirely, even if all the other things I brought up as to
| why the aliens weren't everywhere were not things to take
| into consideration.
|
| So again, still haven't heard any argument why an alien
| civilization achieving the ability to build Dyson
| spheres, even if they did so far enough in the past that
| they would then have adequate time to traverse the galaxy
| afterwards, would then have to be everywhere?
| MattPalmer1086 wrote:
| I'm not sure I understand your argument. There is
| sufficient time, with waves of colonisation to spread
| across the galaxy many times over. This can include
| pauses of thousands of years between colonisation waves.
| Some of those colonies could also build Dyson spheres.
| You would end up with them scattered all over the galaxy.
| Even if the colonies dies out subsequently, the spheres
| would still be detectable.
| bryanrasmussen wrote:
| >I'm not sure I understand your argument. There is
| sufficient time, with waves of colonisation to spread
| across the galaxy many times over.
|
| yes, there is, if the achievement of Dyson sphere
| building happened long enough in the past for there to
| have been sufficient time. 50,000 years ago even, no. The
| length of human civilization is 6000 years approximately,
| what if this civilization much, much older than ours 6000
| years ago just started building it's first Dyson sphere.
| For some reason the assumption is that it was far enough
| in the past that they COULD be everywhere if they wanted
| to.
|
| But then the phrasing is not that they could be
| everywhere but rather they would be everywhere, hence no
| civilization has built Dyson spheres. A lot of this
| theory that the aliens will go about building lots and
| lots of Dyson spheres seems based on the assumption that
| they will be a lot like us, but actually I don't even
| think we would ever build more than one. If we built a
| Dyson sphere it would be because we were at the point we
| needed the energy and we had the technology to do it of
| course, and we had a political system that could harness
| everyone to do it. But once we had the Dyson sphere I am
| not sure we would ever be at the position were we would
| need another one. Since people tend to have fewer kids
| the higher their standard of living it may be that with
| the standard of living of Dyson sphere civ that our
| population would be at replacement level, that is to say
| we would never need to move from one Dyson sphere until
| the sun was just about used up.
|
| So again, sure there is sufficient time with waves of
| colonization (started far enough in the past) - but waves
| of colonization assumes a species that has a colonization
| urge and perhaps one that has a colonization urge greater
| than that of humanity. That's a pretty big if,
| considering all the other big ifs in the whole building a
| Dyson sphere scenario.
| MattPalmer1086 wrote:
| I'm not sure anyone is arguing that aliens who can build
| Dyson spheres HAVE to be everywhere. They could, as you
| say, just build one or two and live there. Or a species
| that colonises could build them as it goes.
| bryanrasmussen wrote:
| That was in fact the statement of the post that I replied
| to "If they can build Dyson spheres, wouldn't they
| already be all over the place?"
| caf wrote:
| They may not be moving around to explore so much as to keep
| their solar system safe.
|
| Galactic orbits are far more chaotic than the sedate stable
| orbits within the solar system - stars closely approach
| each other on a somewhat regular basis.
| bryanrasmussen wrote:
| that's a good point, but I guess at Dyson sphere level a
| star approaching is like discovering oil on your
| property.
| dave_sullivan wrote:
| No Dyson spheres, but there are black holes all over the
| place. Some people think those would make great computing
| devices, many of their origins are not well explained as
| super nova remnants, and they efficiently harness energy from
| companion stars. They have all the properties of Dyson
| spheres but they actually exist. Maybe with advanced enough
| physics, intelligent civilizations learn to manufacture and
| harness black holes, neutron stars, and other dense objects
| for societal benefit.
| jonathankoren wrote:
| > No Dyson spheres, but there are black holes all over the
| place. Some people think those would make great computing
| devices
|
| They're crappy computing devices. Even if you figured out
| how to program one -- and that's an "if" that would make
| Sagittarius A* look like a neutrino -- there's no way to
| read the information out except Hawking Radiation, and that
| would take 10^70 years.
|
| https://youtu.be/0GLgZvTCbaA (8:36)
| alfiedotwtf wrote:
| This is the first time I've heard of this. Wow, yes! A
| blackhole is far more efficient at consuming energy than a
| Dyson Sphere... the hard part though is kickstarting the
| process I guess
| ohyeshedid wrote:
| > If they can build Dyson spheres, wouldn't they already be
| all over the place?
|
| I figure they'd have to be.
|
| They'd need more than a solar system's worth of raw resources
| to build the sphere. They may need more than a solar system's
| worth of resources just to build the tools and craft to be
| able to build the sphere. They're going to need an insane
| amount of production facilities for various components, and
| that's going to take a massive amount of resources. That's
| going to require exploring quite a bit of a galaxy.
| awb wrote:
| > If they can build Dyson spheres, wouldn't they already be
| all over the place?
|
| The number I've seen quoted is 50M years to colonize the
| galaxy: http://www.sentientdevelopments.com/2012/01/new-
| mathematical...
|
| > they calculated that any galactic empire would have spread
| outwards from its home planet at about 0.25% of the speed of
| light. The result is that after 50m years it would extend
| over 130,000 light years, with zealous colonisers moving in a
| relatively uniform cloud and more reticent ones protruding
| from a central blob. Since the Milky Way is estimated to be
| 100,000-120,000 light years across, outposts would be
| sprinkled throughout the galaxy, even if the home planet
| were, like Earth, located on the periphery.
|
| It's actually so fast that advanced civilizations would have
| had time to colonize the galaxy and go extinct many times
| over without us noticing.
|
| Or maybe their spheres were built so long ago they've already
| collapsed and been consumed by the stars again.
|
| It's a great mystery and interesting thought experiment
| though.
| denton-scratch wrote:
| > 50M years to colonize the galaxy
|
| Our ancestors from 50M years ago are all extinct. So a
| civilisation spreading through the galaxy would have
| evolved in all kinds of different ways. It's not obvious to
| me that these diverse evolutionary strands would all still
| be interested in Dyson spheres, or space travel, or even
| astronomy.
|
| There's a belief that's hard to shake off, that the
| properties humans have that we think most important
| represent some kind of evolutionary pinnacle. Typically,
| those properties are language, and a large brain for
| processing language. But if language and a large brain are
| really such great evolutionary advantages, why are humans
| the only creatures on Earth that have evolved those
| properties? Possibly language and a large brain are an
| evolutionary backwater.
|
| At 0.25% of the speed of light, it would take us 1,600
| years to reach Proxima Centauri; but it might take a lot
| longer to reach a star with habitable planets. We'd
| definitely need generation ships. After (say) a million
| years, we'd presumably have evolved to adapt to life on
| generation ships. It's not obvious to me that such
| adaptations would leave us fit to inhabit a planet. And
| perhaps adaptation to life on a generation ship means
| adapting to eating your fellow passengers.
|
| Given the history of humanity, I find it hard to believe
| that the population of a generation ship could survive as
| long as 100 years without war breaking out on-board. We've
| had large brains and language for about 50,000 years, as
| far as I can tell; we've been warring the whole time. Maybe
| large brains and language pre-dispose us to war? If that's
| right, then it seems unlikely that intelligent life would
| ever spread far from it's planet of origin.
|
| I'm very sceptical of the idea that any "civilisation"
| could ever spread far from its home planet. There are two
| things that we refeer to as a civilisation: a culture, and
| a species. Culture changes _very_ quickly - over a single
| lifetime. But on a scale of millions of years, speciation
| is also pretty quick. So I can 't see how any kind of
| homogenous civilisation or species could spread through a
| galaxy. They would have diversified before the train even
| reached its first stop.
|
| So I don't have any insurance against being kidnapped by
| aliens.
| ncmncm wrote:
| Indeed, any culture that actually lasted long enough to
| get to the next star would have become, in the interval,
| comfortable with not being near any star, and could roam
| freely, doing nothing that could attract our attention.
| awb wrote:
| True, unless their lifespans are high enough that a trip
| to a nearby star is only a fraction of their existence
| (or they travel cryogenically and aren't conscious during
| transit).
| awb wrote:
| Much of what you say is reasonable.
|
| Only two minor nits:
|
| > why are humans the only creatures on Earth that have
| evolved those properties? Possibly language and a large
| brain are an evolutionary backwater.
|
| Nearly every animal has language, for cooperation,
| competition, raising their young or to find a mate. Bees,
| whales, primates, birds, etc. all communicate
| strategically with some type of language.
|
| > Given the history of humanity, I find it hard to
| believe that the population of a generation ship could
| survive as long as 100 years without war breaking out on-
| board. We've had large brains and language for about
| 50,000 years, as far as I can tell; we've been warring
| the whole time.
|
| There's been war somewhere the whole time, but not
| everywhere. Costa Rica, Iceland, Panama and several minor
| countries have no military: https://en.m.wikipedia.org/wi
| ki/List_of_countries_without_ar...
|
| It's possible to find many countries who have not fought
| wars in the past 100 years. If you look more narrowly
| it's possible to find communities unaffected by local war
| in hundreds or maybe even thousands of years (in other
| words, they fought a war but did so by traveling great
| distances, not fighting each other).
|
| A ship would be much more like a tiny, isolated island
| colony rather than the geopolitical tensions that
| dominate the news.
|
| Finally, wars rarely result in the extinction of both
| sides. Even if there was a large scale conflict it would
| likely be resolved prior to social collapse. There would
| be little incentive to kill so many of your fellow crew
| to the point where you're putting every survivor at risk.
| mannykannot wrote:
| >> why are humans the only creatures on Earth that have
| evolved those properties? Possibly language and a large
| brain are an evolutionary backwater.
|
| > Nearly every animal has language, for cooperation,
| competition, raising their young or to find a mate. Bees,
| whales, primates, birds, etc. all communicate
| strategically with some type of language.
|
| There is currently only one species on Earth capable of
| even imagining the things being discussed here. On the
| other hand, it seems there may well have been more, but
| the others are now extinct.
|
| One of these issues only we are discussing is the
| evolutionary viability of those abilities, and the fact
| we can do so suggests that it is, to some extent, up to
| us whether or not they will be.
| denton-scratch wrote:
| > Nearly every animal has language
|
| Yes, I elided that bit, in the aim of brevity. I think
| there is a difference between human language and animal
| languages, in that human language is "creative" - we can
| freely create new utterances with new meanings, and
| expect to be understood. We know this of human language,
| but I would be _very_ interested to learn of evidence of
| it in other species (chimps come close).
| denton-scratch wrote:
| It's just struck me that a civilisation propagating
| through space can be envisaged a bit like light-cones, as
| in GR, except that the velocity factor isn't _c_ , it's
| _b_ (the maximum speed at which beings can move), which
| kinda depends on the beings.
|
| But I think the cones thing is still interesting; it
| means that for any given maximum travel speed, there must
| be other civilisations that can never know anything about
| you, nor you about them.
| dnsco wrote:
| It depends on how you define practical value. Immediately
| capitalizable? Probably not outside of Hollywood. Building a
| theoretical underpinning for the future of our species? I hope
| so.
| TheDudeMan wrote:
| This probably has implications around the Fermi paradox and the
| great filter(s). We would like to pass whatever filters are
| ahead of us.
| kragen wrote:
| Was there any practical value in Columbus discovering America?
| If the Aztecs had instead sailed to Europe or Africa and
| discovered them, would that have been of any practical value to
| them?
|
| It's difficult to imagine a discovery that would have _more_
| practical import than the discovery of an extraterrestrial
| civilization.
| ncmncm wrote:
| Hint: Columbus didn't discover America. Millions of people
| already lived there, and knew all about it.
|
| But anyway looking for Dyson spheres will not reveal any
| extraterrestrial civilizations.
| zzt123 wrote:
| I believe the person you are replying to is saying
| "discover" relatively rather than Euro-centrically, as they
| mention a hypothetical Aztecs "discovering" Europe and
| Africa.
| vasco wrote:
| A discovery doesn't have to imply that no living being knew
| about said thing/ place. It can imply only that the person
| or the group of people the person is from learns about this
| new thing. At some point in time nobody in Europe had
| definite proof of how to get to America. You can call
| "europeans learning how to get to America" something else
| other than "discovered America", but what phrasing should
| one use instead?
|
| To make the point, literally nothing can be classified as
| "discovered" under your rules because any alien
| civilization may know about everything we'll ever find or
| figure out, and if they know about it we can't have
| discovered it.
|
| Columbus was a murderer and people in America before he got
| there deserved way better but this type of nitpicking
| correction is just noise if you don't even say what is a
| more appropriate phrase.
| kragen wrote:
| Are you saying that, even if extraterrestrial civilizations
| existed, looking for Dyson spheres wouldn't reveal them? Or
| are you saying that they don't exist, so nothing will
| reveal them? In either case, why?
| ncmncm wrote:
| Looking for Dyson spheres wouldn't reveal them, because
| any extraterrestrial civilization sophisticated enough to
| make one wouldn't need it or want it.
| kragen wrote:
| Unless you originate from a large confederation of such
| extraterrestrial civilizations, there's no way for you to
| know that.
| GlennS wrote:
| Since you're being critical, I think you should suggest a
| better wording for "Columbus discovered American" that you
| think will piss fewer people off.
| ncmncm wrote:
| Columbus stumbled over Hispaniola on what he thought was
| the way to someplace completely different. And then
| insisted he had got there, instead.
| GlennS wrote:
| Perhaps something a little snappier and with less axe
| grinding?
| PeterisP wrote:
| > Was there any practical value in Columbus discovering
| America?
|
| Why, yes, of course - even in the immediate short term the
| ships returned from expeditions with gold and slaves; and
| from the very start the exploration voyages were planned and
| funded solely as a practical endeavor for trade and looting,
| not as an intellectual curiosity.
| wesleywt wrote:
| Research should NEVER be limited by whether it has practical
| value or not. Because we don't know if future generations will
| make it practical.
| XorNot wrote:
| Exactly. Any research which takes something we don't know,
| and turns it into something we now know, is valuable.
| ncmncm wrote:
| Research is ALWAYS limited to what the person performing it
| considered practical. Getting a paper published is as
| practical as most researchers need to get. (Some do more.) If
| they don't publish, they soon don't get to do research
| anymore, and have to start doing what _somebody else_
| considers practical.
| wesleywt wrote:
| You missed the word I wrote "should". Funding agencies want
| to fund only "practical" research. But studying the
| migratory patterns of a single species of butterfly should
| be funded as much as the latest biotech fad that supposedly
| is of "practical value".
| tapas73 wrote:
| All fundamental research is reaserch for the sake of knowledge,
| for the sake of satisfying curiosity.
|
| Once it is done, possibly much much much later, somebody may
| stumble upon it and use it in some creative (and unforseen)
| ways for other research.
|
| On the other hand if you give any probability to alien
| existence, then this is very much practical already in the
| search for them.
| tannhauser23 wrote:
| It's a low cost, low probability way to look for advanced
| civilizations. Chances are low that you'll find anything, but
| hey the data's already here and we have powerful computers so
| let's run some calculations. And occasionally you find weird
| and interesting anomalies that push science forward:
| https://www.space.com/alien-megastructure-mysteriously-dimmi...
| Apocryphon wrote:
| You could possibly win an Ig Nobel Award out of it.
| colordrops wrote:
| Could stars blacked out by Dyson spheres or other technology that
| completely harnesses their energy be an explanation for dark
| matter? Or would this matter not be so "dark" due to the heat
| signature?
| ncmncm wrote:
| In a word, no.
|
| Any sort of Dyson-spherish thing would radiate in infrared, and
| not be dark at all. A long time ago somebody went looking for
| these infrared emitters, and found billions (and billions) of
| them in our galaxy alone. Turns out low-grade infrared-emitting
| stars and star-like things are more common than dirt. There is
| no way to tell them apart from a hypothetical Dyson thingy,
| even if there were any actual reason ever to build one of
| those. (Which, hint, there isn't.)
| MattPalmer1086 wrote:
| The introduction to the article says:
|
| "The observational signatures of such "Dyson spheres" include
| waste-heat from the absorbing sphere, obscured direct star
| light (resulting in both an apparently underluminous star and
| potential temporal variations in brightness) and the effects
| of feedback on the properties of the star from the
| surrounding sphere."
|
| So there are ways to distinguish probable Dyson spheres from
| the majority of these natural infrared sources.
| ncmncm wrote:
| That would depend on somebody, anybody seeing any reason to
| build so much as one of them.
|
| You might imagine a playful civilization building one next-
| system-over to fool planet-bound hicks who actually still
| believe they are a good idea. The hicks restructure their
| whole civilization to be able to mount a trip to visit it,
| and when they arrive find it is all just a mock-up.
| colordrops wrote:
| Dyson, a very smart man, saw a reason to build them. Now
| there may have been some revelations since his time that
| have made it obvious that they are not a good idea, but
| clearly that information has not spread widely. Care to
| enlighten us?
| MattPalmer1086 wrote:
| Sure, there are good and interesting arguments as to
| whether anyone would bother, but that's orthogonal to
| whether we can distinguish them from natural sources.
|
| EDIT: but I like your idea, sounds like it would be a fun
| short story!
| awb wrote:
| I think most if not every galaxy has dark matter so if it's
| Dyson spheres that would mean that nearly every galaxy was
| colonized with Dyson spheres in the same way (except ours
| because we don't have evidence of a galaxy-wide civilization).
| maxander wrote:
| Indeed, Dyson spheres would need to release some amount of
| waste heat, due to the laws of thermodynamics. If there were
| too many of them that heat would be visible (at least to
| infrared telescopes,) so we know that's not the explanation for
| dark matter. Same with dust and other non-luminescent matter-
| it's all way more visible than dark matter has to be, somehow.
| freemint wrote:
| What prevents that waste head being as warm ad the peak in
| cosmic background background radiation
| ncmncm wrote:
| Literally every last thing in the whole universe that can
| radiate heat is at least as warm as the cosmic background
| radiation. You cannot shed _any heat at all_ unless you are
| warmer than the background radiation, because you would be
| absorbing as much heat from it as you radiate. If you were
| colder, you would necessarily be absorbing more.
|
| Thermodynamics does not play around.
| buryat wrote:
| what would prevent an intelligent civilization from covering
| all other stars in dyson spheres?
|
| and the dark matter is everywhere (almost, there're galaxies
| without it) which would mean that most of the universe has
| intelligent life but then why there's no other signals?
| something should've leaked/pointed at it
| ncmncm wrote:
| What would prevent it? Good sense. To be able to do it is to
| know better than to bother.
| mabbo wrote:
| A fun thought experiment to counter this idea.
|
| Let's presume that the universe is full of Dyson Spheres, and
| the gravity they produce is what we call "Dark Matter". Well,
| Dyson Spheres must be built, right? So earlier in time, there
| would be fewer of them, and later in time there would be more
| of them.
|
| When we look into the sky, we look back in time. So if this
| were the case, when we look backwards in time we should see
| more brightness and less dark matter effects, while closer in
| time we should see less brightness and more dark matter
| effects.
|
| We do not see those patterns. Dark matter is consistent over
| time, as far as we can tell, and brightness from stars remains
| what we would expect.
| ardit33 wrote:
| Dyson spheres are just inane.... sorry but they don't make sense.
|
| Any advanced form of civilization that can build one, probably
| figured how to do fusion efficiently locally and doesn't have to
| build these insanely inefficient energy harversters.
|
| Keep in mind that the sun is very inefficient at energy release.
|
| Dyson sphere prediction is like predictions in the 1800s how we
| would have coal and steam powered airships to travel around.
|
| The reality is that steam via coal fire is too inefficient. Coal
| is just too heavy. Jet fuel is much more efficient/energy dense
| and not need to build giant airships.
|
| Same with any advanced civilization. Dyson spheres just don't
| make sense, but they sure make good sci-fi movies/stories for the
| gullible.
| AprilArcus wrote:
| The ingredients for fusion reactors (deuterium, tritium and
| helium-3) are rare, not fully reacted intermediate byproducts
| of the proton-proton cycle that powers the sun.
|
| The likeliest case for a Dyson Sphere civilization would be
| some sort of solar powered Gray Goo von Neumann replicator.
| ardit33 wrote:
| In theory you can fuse up to Iron.... the last stage of
| stars. You are not limited to just Hydrogen.
| tapas73 wrote:
| I assume that some of fusions done by the star are net
| energy consumption (i.e. not usable for energy production)
| ncmncm wrote:
| You assume wrong. Anything beyond iron is made in a
| supernova, i.e. in the last moments before it is not
| really a star at all, anymore.
| chii wrote:
| takes a star's worth of gravitational force to push atoms
| like those together in the core to produce fusion.
|
| To reproduce such heavier elements in fusion reactors on
| earth would require, likely, a much higher energy than the
| output.
| ncmncm wrote:
| The ingredients for the most primitive, low-tech, hayseed
| fusion reactors are sort of rare. But anybody with any
| sophistication at all has no need for such primitive
| processes. They fuse plentiful regular hydrogen, helium, and,
| not to be wasteful, whatever they get from fusing those, too.
| fullstackchris wrote:
| I'm right here with you, love the haters too that downvote you.
| The real takeaway is simply this: we don't (and can't) KNOW
| what type of energy advanced civilizations will have (and we
| might not even be able to understand it if we saw it!), and
| collective scientific time is much better spent on things that
| we DO know, like searching for bio markers similar to earth.
| empiricus wrote:
| "do fusion efficiently locally" - with what? The vast majority
| of available fuel is in the stars. Dyson spheres are different
| than planet size civilization. For planet size civilization,
| with population in the order of billions/trillions ppl, local
| fusion is probably good enough. But for populations a billion
| times bigger, so billions of billions of ppl, you need dyson
| spheres, or alternatively, a way to destroy stars and get the
| raw hydrogen - probably harder to do.
| ncmncm wrote:
| Hint: Jupiter is made mostly out of hydrogen. Saturn too.
| Uranus and Neptune, if those get used up. Also plenty of
| helium, maybe even more useful.
|
| Also: the Pacific, Atlantic, Indian, and Arctic oceans are
| made of _water_ , which has hydrogen in it. Also all of the
| Antarctic and Greenland ice, the Great Lakes, Caspian Sea,
| Lake Baikal, and Lake Victoria.
| csee wrote:
| Why wouldn't they do fusion locally but _also_ build a
| Dyson sphere? Doing only the former produces less energy
| than doing both the former and the latter.
|
| The view that they wouldn't do both is premised on the
| assumption that they won't need or want that much energy,
| combined with the assumption that the problem of disposing
| of the waste heat makes the extra energy not worthwhile.
| akvadrako wrote:
| Jupiter is much smaller than the Sun, so it isn't really
| relevant what it's made of.
| ncmncm wrote:
| It is _right there_ , completely unused, and not too hot
| to get close to.
|
| Most likely you would use up Neptune first, and save
| Jupiter for later.
| sgillen wrote:
| Wouldn't the theoretical maximum output of a Dyson sphere (the
| entire output of a star) dwarf that of doing fusion yourself
| locally?
| ncmncm wrote:
| If you were using that much energy you would have the much
| bigger problem of disposing of all the waste heat afterward.
| You could not do that close to a star.
| freemint wrote:
| Not necessarily as some stars are wasteful (use energy to
| fuse bigger atoms) or have material in the core it can't
| fuse. If you are just concerned with energy output per mass
| you can do better artificially in theory
| TheDudeMan wrote:
| It is not very meaningful to talk about the efficiency of
| something that is already running and needs no more fuel for
| the next billion years.
| pengaru wrote:
| It's worth noting "Dyson Sphere" is a product of sci-fi
| literature. Freeman Dyson himself only described an "artificial
| biosphere" in some paper he published, sci-fi authors mistook
| him literally (or were just being creative). He wasn't even
| describing anything resembling a physical sphere surrounding a
| star.
|
| He speaks to the subject in this excellent interview playlist,
| link is to the specific Dyson Sphere part:
|
| https://www.youtube.com/watch?v=GPB775_BZlw&list=PLVV0r6CmEs...
| denton-scratch wrote:
| > the sun is very inefficient at energy release
|
| I'm not clear what is meant by "inefficient at energy release".
| Does that mean that the in the process of energy release, some
| of the energy is converted into heat? I.e., more energy?
| jallen_dot_dev wrote:
| Presumably if your super-advanced civilization needed more
| energy than could be fused from all the matter in a planet, you
| would have to get it from a star.
| fullstackchris wrote:
| Presumably if you are a super-advanced civilation, you would
| get power from what would appear to us mere primates as
| essentially thin air, in a fashion we can't even fathom.
|
| "Any sufficiently advanced technology is indistinguishable
| from magic."
| jallen_dot_dev wrote:
| So a Dyson Sphere is inane, but energy from nothing isn't?
| Got it.
| ncmncm wrote:
| Or use a bigger planet.
| denton-scratch wrote:
| If a Dyson sphere captures a large proportion of the radiation
| from a star, what is the destiny of that energy?
|
| It gets converted into other kinds of energy, and eventually
| becomes waste energy, ending up as low-grade heat. Hence the
| search for infra-red sources. But the amount of energy that a
| Dyson sphere absorbs must be equal to the amount of low-grade
| heat it radiates; so I'd expect a Dyson sphere to be very bright
| in infra-red - much brighter than brown or red dwarfs.
|
| Such an object should be quite easy to spot.
| jcims wrote:
| That's sounds like something that someone from a Type I
| civilization would say.
| denton-scratch wrote:
| Wouldn't know; I've never met anyone from a Type I
| civilisation.
| dr_dshiv wrote:
| I once got the chance to ask freeman dyson what he recommended
| educationally, for children, to produce more freeman dysons.
|
| He didn't hesitate. He said we need to teach children genetic
| engineering to children in such a way that they could approach it
| playfully. Only then would we have a chance of developing warm
| blooded plants which would be essential for colonizing the
| asteroid belt.
|
| So, if anyone has any ideas for that...!
| dnsco wrote:
| Was going to ask for someone smarter than me to explain what
| warm blooded plants would do, but decided to google it and
| found this speech by dyson:
|
| https://www.youtube.com/watch?v=_yzgPMwshqE
| mrfusion wrote:
| On that vein I had the idea of engineering floating plants to
| live in the nice altitude of venuses atmosphere.
|
| Oxygen plants produce would actually be a lifting gas on
| Venus so pretty doable. Plenty of sunlight and co2 too.
|
| But I hit a wall with the Mack of water in the atmosphere.
| miki_tyler wrote:
| I am obsessed with Venus and I have thought a lot about
| acidophilic prairies floating on the Venus atmosphere. They
| would be indistinguishable from land if you are standing on
| top of them, you can build your Hobbit house there. It is
| an amazing concept!
| mrfusion wrote:
| Wow I love that idea. So the plants would absorb the acid
| in the atmosphere?
|
| I guess you'd just need to provide your own water?
| Firmwarrior wrote:
| Quick excerpt:
|
| "The first species to emerge from a Noah's Ark egg will be
| warm-blooded plants designed to collect energy from sunlight
| and keep themselves warm in a cold environment. "Plants could
| be engineered to grow greenhouses the way turtles grow
| shells" The greenhouse would consist of a thick skin
| providing thermal insulation, with small windows to admit
| sunlight. Outside the skin would be an array of simple
| lenses, focusing sunlight through the windows into the
| interior. Groups of greenhouses could grow together to form
| extended habitats for other species of plants and animals. In
| that way, "We will be the machines getting life to grow all
| over the universe."
| kevin_thibedeau wrote:
| Plants like that already exist minus the exothermy.
|
| https://en.m.wikipedia.org/wiki/Leaf_window
|
| https://en.m.wikipedia.org/wiki/Mesembryanthemum_crystallin
| u...
| Qem wrote:
| Cycads are kinda warm-blooded plants. They heat-up their
| cones to attract pollinators. Oliver Sacks mentions this
| fact in his book, The Island of the Colorblind. See https
| ://www.sciencedaily.com/releases/2007/10/071004143133.h..
| .
| [deleted]
| dr_dshiv wrote:
| Is there a botanist in the house? How do we crossbreed
| plants this radically different?
|
| Here's the Wikipedia on thermogenic plants. I did not
| know skunk cabbage can melt snow! I used to have it in my
| back yard.
| https://en.wikipedia.org/wiki/Thermogenic_plant
|
| Here's a paper on the genetics and cellular biology of
| thermogenesis in skunk cabbage:
|
| https://pubmed.ncbi.nlm.nih.gov/21955303/
| moralestapia wrote:
| Are they thermodynamically feasible, though?
|
| Assuming perfect efficiency in capturing whatever sunlight
| they get, perfect conversion to chemical storage (i.e.
| sugars, or any other fancy molecule with energy-intensive
| bonds) and a perfect conversion from that to heat. Would
| there be enough energy to keep the plant warm? Against a
| temperature difference of 40oC+?
| vimax wrote:
| The hot side of JWST is currently 57c, that's a lot of
| energy to capture.
| moralestapia wrote:
| Ok, but then (and my curiosity is sincere) why would you
| need a plant to "stay warm" at 57degC. Because of the
| night? But that could be solved with some sort of passive
| solution that buffers the temperature along the day, not
| neccessarily producing its own heat.
| blacksmith_tb wrote:
| Would night have to happen? In lots of orbits couldn't
| the plant keep the window facing the sun continuously? I
| assume in general staying warm is a plus for making
| reactions (like photosynthesis) easier and faster, so
| better for building a big living colony.
| vimax wrote:
| If it's an asteroid what is night even like? It seems
| like it'd be a lot less extreme than a planet.
|
| I could imagine a plant that walks along the surface to
| stay in the sunlight.
|
| Maybe lay down roots all over the asteroid to do the
| refining and have long tethered leaves always in the sun.
|
| If the leaf stalks can grow at the same rate as the
| asteroid rotation, just keep growing and wrapping the
| asteroid until you're left with nicely spooled refined
| materials.
|
| I don't think a hot blooded plant is practical or
| necessary, but there is enough energy that it could be
| possible.
| hnmullany wrote:
| I think we've learned a lot about soil complexity since then
| and how hard soil is to create.
| marcosdumay wrote:
| Soil for our plants is hard to create.
|
| That doesn't mean soil for any kind of organism is as hard.
| There are many of them that don't need all that complexity
| even on our world that doesn't strongly select for it.
| tannhauser23 wrote:
| His article, "Warm-Blooded Plants and Freeze Dried Fish", is a
| classic:
| https://www.theatlantic.com/past/docs/issues/97nov/space.htm
|
| Highly recommended.
| dghughes wrote:
| I don't see why we need warm-blooded plants. I had spinach
| growing in my garden in 2020. Usually I pull up anything in the
| garden and till it but in fall 2020 I didn't. Spring 2021 and
| there was the spinach green as emerald. All through -20C,
| freezing rain, snow, just all around cold weather it was fine.
| edit: forgot to add frost in the ground probably down 60cm or
| 75cm so it's also affecting roots. Spinach is cold loving but I
| though it was amazing. Even more impressive than grass on a
| lawn which often is fescue, rye, bluegrass.
| jsiaajdsdaa wrote:
| Just a gamified website that regurgitates textbook material? I
| could do it this weekend if you like.
| fullstackchris wrote:
| Always have to comment on the meme Dyson spheres posts with the
| following: has anyone ever thought, for one second, that a
| civilization capable of building these massive energy systems
| would actually be capable of generating energy in other different
| ways that we can't even imagine? This whole "Type I, II, III"
| civilization crap is stupid because it is based off one paper, of
| one guy, who had a creative idea. Props to him for the
| creativity, but millions of scientists every day have possibly
| creative ideas about space fairing civilizations. Its like sci-fi
| novels creeped into real science. Literally ape brain to just
| "wrap a star and capture its energy!"
|
| I think most people "like" the idea because it's so tangible. But
| that doesn't make it any more or less likely that it actually
| exists or makes sense.
| joe_the_user wrote:
| I fully agree with the sentiment.
|
| Speculation what form future tech takes should have be broad
| and uncommitted.
|
| * Given our current knowledge, Dyson Spheres are essentially
| impossible (just lesser-known point is that unlike planet, full
| Dyson Sphere or Ring World would not be attracted to the star
| that it would be built around, so it would have to be guided to
| move with it - see Larry Niven's Ring World Engineers). * What
| a civilization would do with all the energy, whether it would
| want it, etc are other unknowns.
|
| As you say, turning one person's clever idea into a whole
| research program at the very least neglects other great scifi
| novels.
| rini17 wrote:
| I think it's not only about energy generation but what would
| massive civilization without dyson spheres imply:
|
| 1. sidestepping thermodynamic laws - to allow massive energy
| use without detectable waste heat
|
| and/or
|
| 2. sidestepping time lags - so that the system does not need to
| be bunched as closely together as possible to allow for
| efficient communication and flows of material
| TheOtherHobbes wrote:
| Dyson Spheres are fundamentally unphysical. The stability
| constraint on a complete sphere turns out to be less of a
| problem than it might seem, but there are still huge issues
| with stresses - Sphere Quakes.
|
| And before you can build a full Sphere you have to build a
| partial Sphere. Which is where stability will really kill
| you.
|
| Dyson Swarms might be more practical, but you still have a
| computability problem because you have an insanely huge
| number of objects in orbit and you somehow have to keep them
| from colliding with each other.
|
| Not so much a three body problem as an n body problem. With a
| built-in light lag delay of (at least) minutes.
|
| I'm not sure if anyone has modelled that, but it would be
| hilarious if the computing and station-keeping power
| requirements turned out to be a significant proportion of the
| available energy,
| rini17 wrote:
| But you did not exhaust all the options. What about
| spherical constellation of energy gathering sails that stay
| mostly in place? Can autonomously maintain their position
| with help of solar wind.
| perihelions wrote:
| Or even pure radiation pressure. They balance out
| somewhere around 10^-3 kg/m^2; thinner than that and you
| have a solar sail.
| PeterisP wrote:
| > spherical constellation of energy gathering sails that
| stay mostly in place?
|
| Wait, what? You can't have a spherical constellation of
| unconnected stuff that mostly stays in place, that's not
| how orbits work. You can have a single orbital ring, but
| a sphere consisting of many circular orbits would have
| these orbits intersect with very large relative movement.
| If you're thinking about non-rotating constellation where
| the gravitational pull is balanced by solar wind, the
| problem is that they have gravitational interaction with
| each other and the planets so it's inherently unstable,
| they would "want to clump up" and as soon as they do, the
| balance is disrupted as the same mass has less solar
| pressure and it starts to fall into the sun.
| edgyquant wrote:
| It's probably just that colonizing the entire galaxy is
| really hard and no society ever has an economic need to.
| Populations don't expand exponentially forever, the recent
| explosion is an effect of the industrial revolution, and any
| species that gets a certain size breaks up into subspecies
| and starts competing with each other.
|
| There could very well be individual dyson swarms out there
| and we haven't seen them or haven't realized that's what they
| are. But building them around every star in the galaxy is
| something I'll never understand why it's taken as a given.
| ben_w wrote:
| Frequently; that comes up in basically every Issac Arthur video
| on the topic.
|
| Unless such a civilisation can dump the waste heat as something
| other than infrared light or send that waste to somewhere other
| than the visible universe, it's still extremely visible.
| ncmncm wrote:
| The odds that anybody smart enough to be _able_ to build such a
| thing would not be smart enough to recognize what a bad idea it
| is, is closer to zero than any mere human can conceive of.
| kragen wrote:
| People smarter than you, like Freeman Dyson, have thought
| otherwise. More generally, a human putting long odds on what
| anybody much smarter than mere humans would do is self-
| evidently a way to lose bets. Can you imagine a dolphin or a
| crow successfully predicting the outcome of the US's
| withdrawal from Afghanistan?
| ansible wrote:
| OK, let's talk about energy generation for a minute. If we
| assume there exists some completely new physics, then... that
| could be anything. Advanced civilizations could take on any
| form. We can speculate all day about magic and elves too.
|
| If we _don 't_ assume any new physics and / or thermodynamics,
| then that constrains the discussion a lot. We have two basic
| ways of generating a lot of power, fission and fusion.
|
| Fission uses fissile materials, which are relatively rare, not
| just on Earth, but in the Universe at large. There's plenty
| enough for us at our current energy generation needs, but not
| nearly enough for a galaxy spanning civilization. That leaves
| us with fusion.
|
| Fusion reactors, as currently conceived use Helium-3 or
| something like that. There's enough of that around the solar
| system to power a civilization for a long time, even though the
| mass of oddball elements like Helium-3 make up a very tiny
| fraction of the total mass of the solar system (which is mostly
| the Sun with a smidgen of Jupiter).
|
| Most of the solar system's mass is plain hydrogen: one proton
| and one electron.
|
| Is it possible to fuse most / all of this mass in the solar
| system? Yes. We won't go into the details, but trying to fuse
| regular hydrogen (regular protons) together is highly
| impractical outside of the core of a star. Preferably a red
| dwarf type star which can more completely burn its fuel than
| our own Sun will, and live a lot longer to boot (a trillion
| years vs. ~10 billion for the Sun).
|
| So now we're talking about some kind of solar collectors, and
| if you want to collect _all_ the energy from a star, you want a
| sphere of some sort. Or a swarm of objects in orbit achieving
| the same effect.
|
| Hence Dyson sphere / swarm.
| raverbashing wrote:
| > and if you want to collect _all_ the energy from a star,
|
| For what? What are you doing with it? Not to forget the fact
| that all energy used eventually turns into heat. All of it
| (with the exception of electrochemical transformations).
| You're bringing all of that into Earth you're cooking
| everybody alive.
|
| How are you bringing that energy from the sphere to (wherever
| place)?
|
| Putting solar panels on Earth itself works much better. Heck,
| make a Dyson sphere _on Earth_ (facing outside), that makes
| more sense.
| ben_w wrote:
| > Heck, make a Dyson sphere on Earth (facing outside), that
| makes more sense.
|
| I'm missing something here, because even if we decided to
| build a Dyson swarm _of course_ we are going to start with
| putting solar on and around Earth because this is where all
| the stuff we care about is.
|
| That's just the first step in a journey of a miles miles.
| (TIL where that quote comes from: https://en.wikipedia.org/
| wiki/A_journey_of_a_thousand_miles_...).
|
| This seems so obviously it can't be what you're taking
| about though.
| ansible wrote:
| It is typically assumed that by the time you are making a
| Dyson swarm, that most life exists digitally. And spread
| out through the solar system.
|
| So in the best case scenario, you are powering
| computronium, upon which trillions of sophonts live out
| their digital lives. Hopefully doing some science, or at
| least playing some interesting games. A vast distributed
| network.
|
| In the worst case scenario, Blockchain and spam emails.
|
| Either way, people will put that energy to use.
|
| With a Dyson swarm, energy is received on the inside,
| towards the star, and heat is radiated outward. Lower power
| systems can run off the heat radiation of the inner swarm
| similarly. It is all eventually released as very low level
| heat, but diffused across the entire outer surface of the
| swarm. No hotspots... because someone would come along and
| use it.
|
| The Earth would also likely be deconstructed by this time,
| so don't worry about the biosphere, there won't be any.
| naasking wrote:
| > For what? What are you doing with it?
|
| One example: powering lasers for light sail ships to
| colonize other star systems.
| raverbashing wrote:
| You are not pushing a light sail ship to another star
| system, sorry.
|
| Light sails are "theoretically" possible but you don't
| need that much energy to push something that's feasible
| to push.
|
| Or better, there's a better source of light radiation:
| the sun itself. No need for a laser, just use a focusing
| mirror and you can have 100x more pressure than just from
| the sun itself.
| naasking wrote:
| Why not? Light sails can reach 10% the speed of light,
| and sending out thousands of colony ships in multiple
| directions seems like a feasible way to colonize a galaxy
| relatively quickly.
|
| As the other poster mentioned, harnessing the sun's
| energy and turning it into a better form suited for light
| sails is the way to go. Sailing on the solar wind within
| a star system is a different tech with a different
| purpose.
| ansible wrote:
| Light sails are practical, and have already been tested
| in orbit.
|
| https://www.planetary.org/articles/lightsail-2-successful
| -fl...
|
| Light from the Sun isn't coherent, and you can't focus it
| with mirrors very far away. Lasers have many orders of
| magnitude less divergence when talking about distances
| measured in light-years.
| naasking wrote:
| > We have two basic ways of generating a lot of power,
| fission and fusion
|
| I think there are more. Like radiation from evaporating black
| holes.
| ansible wrote:
| > _I think there are more. Like radiation from evaporating
| black holes._
|
| _Evaporating_ black holes?
|
| Yes, if you are willing to wait a very, very long time, and
| have collectors over a large area.
|
| However, if you want to get stuff done before your protons
| evaporate, you could instead throw matter _into_ a black
| hole, thus increasing its mass. The radiation given off by
| the accretion disc is substantial, and can be collected...
| over a large area.
|
| IIRC, the mass-to-energy efficiency is something like 40%,
| which is really good.
|
| They are a little difficult to set up however...
| naasking wrote:
| I mean, we're talking about timescales and construction
| projects like Dyson spheres. It's entirely feasible that
| people with such technology could create microscopic
| black holes that evaporate quickly for these purposes.
| Hawking radiation at this scale is substantial.
| ansible wrote:
| Ah, yes, I do recall reading about that somewhere.
|
| That is an interesting prospect, with a very high mass-
| to-energy efficiency. Of course it requires careful
| management of inflowing matter. And you can shut if down
| if needed by stopping the inflow, assuming you have
| enough stored energy to recreate the micro black hole
| sometime later.
| naasking wrote:
| You'll probably enjoy this video:
|
| https://youtu.be/EzZGPCyrpSU
|
| Good channel too.
| kragen wrote:
| A Dyson sphere is technically possible without any new
| physics with a few decades of work. By contrast, while we
| have the physics to analyze how black holes much smaller
| than a proton would behave, we have no plausible way to
| go about making one.
| naasking wrote:
| > A Dyson sphere is technically possible without any new
| physics with a few decades of work
|
| Not a chance. I disagree 100%. The materials science and
| orbital mechanics for coordination alone are way beyond
| our capabilities.
| emteycz wrote:
| Dyson sphere as conceived by Dyson himself is a swarm of
| orbiting objects, not a literal sphere around a star
| (that's Star Trek interpretation). We could start sending
| out solar panels to orbit the Sun today, and start adding
| space stations later this/next decade.
| marcosdumay wrote:
| I wonder how practical it is to sustain right-sized
| artificial black holes. Small ones should irradiate much
| more.
| eloff wrote:
| It's premature to say what's practical with fusion and what
| isn't. It's entirely possible that we find a way to build an
| efficient hydrogen fusion reactor. In which case it might not
| make sense to travel so far away from our planet just to
| collect energy from photons when that costs more than just
| doing the fusion ourselves. Remember it's actually more
| expensive to travel towards the sun than away from it
| (because you have to shed velocity relative to the starting
| velocity on Earth.) It's too arrogant to think we know the
| answer to that now.
| ansible wrote:
| > _It 's premature to say what's practical with fusion and
| what isn't. It's entirely possible that we find a way to
| build an efficient hydrogen fusion reactor._
|
| Would it not surprise you that fusion in general has been
| studied extensively by physicists for nearly a century? It
| takes very high temperatures, pressures _and_ quantum
| tunneling to get two protons to fuse.
|
| Here's some reading to get you started:
|
| https://courses.lumenlearning.com/physics/chapter/32-5-fusi
| o...
|
| Or read about how the Large Hadron Collider works.
| eloff wrote:
| It doesn't surprise me. Your arrogance does though, I
| didn't expect you to double down on an unreasonable
| position. How can we possibly know what we don't know
| yet. Not about how fusion works in theory, but about the
| limits of the economics of fusion reactors at any point
| in the future.
|
| What I'm saying is it's too soon to say what's possible
| with fusion and what isn't. We don't even have a break
| even reactor yet. We can even say for certain that we
| ever will.
| akvadrako wrote:
| Probably not. Energy is (at least to a high approximation) a
| conserved resource and stars are the most massive objects
| around besides black holes.
| TaylorAlexander wrote:
| Based on our understanding of science. But 200 years ago the
| idea of having a conversation with someone 1000 miles away
| seemed quite impossible. Is it so hard to imagine that out of
| the possibly hundreds of millions of civilizations in the
| Milky Way, someone has found a way to extract energy from the
| universe in a way which seems physically impossible to us?
|
| I'm always very open to the idea that there could be a lot of
| physics we don't understand yet. We could be at 0.1% of an
| understanding of the basic laws of the universe. I'm not
| saying I think that is likely or unlikely, but I do think it
| is possible.
| gerikson wrote:
| > But 200 years ago the idea of having a conversation with
| someone 1000 miles away seemed quite impossible
|
| In 1822 the Chappe optical telegraph had been in use since
| the Revolution, and the electric telegraph was ~20 years
| away. You'd have had to be singularly unimaginative not to
| envision an eventual extension to instantaneous voice.
| TaylorAlexander wrote:
| Ah, I guess I was referring specifically to radio
| transmission. You could say 400 years ago if that
| matters. A distant civilization could be 1 million years
| ahead of us.
| larksimian wrote:
| Eh, it's typical retrofuturism type stuff, extending current
| technologies quantitatively rather than trying to predict
| categorical changes in available tech.
|
| Also the issues of dyson spheres aren't that bad. they could
| for instance channel the heat loss energy in a narrow beam out
| of the galactic plane so at least they'd be hard to spot by
| other galactic observers.
| edgyquant wrote:
| I definitely agree with you. I'm not a physicist but I did
| watch a ton of pop sci growing up and saw so much stuff about
| Dyson sphere, Fermi paradox, etc. I got so bored of it and hate
| how it drags down most discussions about potential alien life
| etc. The Fermi Paradox itself was supposed to proof we've got
| something wrong, not that we're alone in the universe and
| something scary lurks.
|
| I think the answer may be that most civilizations never need or
| want to colonize everything in sight. It could also be
| political: no species gets to the level of being able to build
| structures like this without breaking up into competing
| polities. We think about colonizing everything because we're
| still in the mode of a creature who evolved on a planet and
| spread out everywhere.
|
| It's probably the case that with fusion dyson swarms aren't
| used due to the opportunity cost of building them. In 1-200
| years we'll find the idea of surrounding the sun with metal as
| laughable as there being canals on Mars.
| voldacar wrote:
| I agree. A hyper-advanced race would probably want to
| disassemble the star and use its hydrogen for something more
| efficient than the main-sequence nuclear process, which is
| pretty wasteful.
| bbarn wrote:
| Maybe this is a stupid question, but is there actually enough raw
| material in the solar system to cover the surface of our star and
| build the necessary machinery to keep it in place, collect its
| energy, etc.?
| kragen wrote:
| You don't put it on the surface of the star; you orbit at a
| distance far enough away to maintain a reasonable temperature.
| Current solar panels are about 300 grams per square meter, but
| there are much opaquer materials than silicon, so you can
| probably get down to a hundredth of that. A sphere at the
| radius of Earth's orbit would be 2.8e23 square meters and thus
| at 300 grams per square meter 8.4e22 kg. Earth's moon masses
| 7.3e22 kg, while Jupiter masses 1.90e27 kg. So there's at least
| five orders of magnitude more raw material than you need.
|
| If you happened to live in a planetary system without adequate
| gas giants, you could probably find some way to scoop mass off
| the surface of your star or capture it from coronal mass
| ejections, then use fusion to transmute it into the materials
| you need. Even Sun is 1.90e30 kg, and it's rather small as
| stars go.
| Smaug123 wrote:
| I'm sure you already know this, but GP probably doesn't: I
| love https://en.wikipedia.org/wiki/Star_lifting for very many
| reasons.
|
| 1. "Stellar husbandry". That phrase alone is worth the price
| of admission.
|
| 2. The idea of doing mass spectrometry on a jet of matter
| coming out of a star to separate it out into streams of
| hydrogen, deuterium, helium, etc.
|
| 3. The idea of creating artificial gas giants as a storage
| mechanism.
|
| (The list goes on, but 3 is a magic number.)
| kragen wrote:
| I didn't! Thanks!
| dmead wrote:
| Probably not. I was under the assumption we could build a Dyson
| swarm however.
| digitalronin wrote:
| There's plenty. The vast majority of the 'shell' would be solar
| concentrators - basically aluminium foil or something like it.
| You can make a LOT of that by dismantling a few asteroids,
| never mind a planet or two.
|
| Isaac Arthur's youtube channel goes into this in some depth
| (and is generally excellent, IMO). Here's an episode on Dyson
| Spheres:
|
| https://www.youtube.com/watch?v=HlmKejRSVd8
| TaylorAlexander wrote:
| It's probably very difficult structurally to build an actual
| sphere, since the poles would not have any orbital velocity and
| the whole sphere would want to flatten. Unless there is a way
| to do some kind of anti-gravity that humans just haven't
| discovered (which is a possibility that seems plausible).
|
| But there is also the Dyson swarm, which is like a starlink
| constellation orbiting a star and designed to collect as much
| energy as possible.
|
| Anyway I don't know the answer to your question, but if we
| ignore structural problems with a sphere we could imagine a
| material a few atoms thick, like a giant carbon nanotube
| structure. Then one wonders how much material there is in
| Jupiter as an approximation of total matter in the solar
| system. I will leave the calculation as an exercise to the
| reader. ;)
| Blammar wrote:
| I believe Dyson spheres don't rotate, so they just have to be
| able to handle the stress of the central sun pulling
| uniformly on the surface.
|
| Per the Ringworld not being stable, I think the same math
| applies to the sphere as well as the Ring, so the sphere will
| need attitude jets to maintain position with respect to the
| central sun.
|
| Dyson swarms seem drastically easier to construct. We could
| build one example of that habitat fairly soon!
| TaylorAlexander wrote:
| Ahh a non-rotating sphere makes sense! If it is light
| enough then solar pressure could help keep it up too, and
| it could have openings to adjust pressure which would serve
| as attitude jets. Hmmm this does seem possible after all,
| thanks for the tips!
| buryat wrote:
| 2 _pi_ r^2 vs 4/3 _pi_ r^3
|
| plenty of material to capture the surface
|
| + you don't need a sphere, a ring/few rings would be enough
| Jimbonius wrote:
| galaxyLogic wrote:
| Careful with that axe Eugene
|
| https://youtu.be/YtZqNAI4pBk?t=93
| dang wrote:
| " _Eschew flamebait. Avoid unrelated controversies and generic
| tangents._ "
|
| https://news.ycombinator.com/newsguidelines.html
|
| We detached this subthread from
| https://news.ycombinator.com/item?id=30394933.
| tapland wrote:
| Start a cult for selective breeding is probably the easiest
| way.
| kdioo88 wrote:
| T-A wrote:
| https://en.wikipedia.org/wiki/Space_Seed
| dillondoyle wrote:
| The problem with 'natural' eugenics to me seems the 'un fit'
| castoffs.
|
| Seems we could accomplish the same thing or better with science
| and genetic engineering.
|
| While likely still restricted to the rich - at least at first -
| it doesn't have the oppression side to it.
|
| But that thought experiment can go too far too. like elites
| giving themselves more and creating an even more lopsided
| world.
| teh_infallible wrote:
| We could create a race of strongmen, based on genetic mutation
| and evolution!
| Iwan-Zotow wrote:
| dang wrote:
| Please don't take HN threads further into flamewar. Not
| what this site is for.
|
| https://news.ycombinator.com/newsguidelines.html
|
| Edit: we've already asked you this, and you've
| unfortunately been doing it repeatedly. Could you please
| not? If you'd make substantive points thoughtfully, that
| would be much better.
| Teever wrote:
| What kind of eugenics are you proposing? I know that the notion
| of eugenics has got a bad rap but I'm a bit concerned with your
| wording because it seems to indicate that you have in mind the
| kind of eugenics that gives the whole notion a bad rap.
|
| When you say 'we could do some eugenics' do you mean the kind
| of top down, centrally planned by absurd edict shit that we saw
| from central Europe in the early 20th century that was
| influenced by North American culture that lingered well into
| the mid 20th century?[0]
|
| Or do you mean the kind of self empowered eugenics of the late
| 20th century where women found themselves with newfound means
| to decide their reproduce destiny for themselves?
|
| What are your thoughts on the burgeoning 21st century
| development where currently upperclass people are finding
| themselves in the economically viable position to select and
| potentially modify embryos for implantation?
|
| How do you think that we as a society should bridge the gap
| between where we are now with eugenics and where we could be,
| and how does that tie into where you think we could go as a
| species either interplanetary or beyond?
|
| [0] https://en.m.wikipedia.org/wiki/Provincial_Training_School
| AlexAltea wrote:
| > eugenics has got a bad rap
|
| Mostly in Europe and North America, and territories
| culturally-influenced by them, largely as a side-effect of
| historical events 80 years ago.
|
| Other parts of the world have different opinions on the
| matter.
| Teever wrote:
| I'm not sure what your reply either ads to or disputes of
| my original comment.
| AlexAltea wrote:
| Neither. I just thought it opens an interesting question:
| What happens in the long run if some parts of the world
| embrace eugenics and gene therapy (in whatever form),
| while others do not, e.g. under ethical grounds or simply
| different priorities.
| Teever wrote:
| Further class segmentation and ultimately speciation once
| populations have grown so far apart that they can no
| longer procreate.
|
| I can't recall the title of an Australian gov't
| commissioned paper on the subject but this was ultimately
| the conclusion.
|
| The paper also pointed out that domestic attempts to
| regulate these acts would ultimately be futile because
| people were already traveling abroad (specifically Italy)
| to seek out reproductive/eugenic services that were not
| legal in Australia.
| ben_w wrote:
| My expectation would be a similar result in humans to
| what we observe in all the non-humans we've been
| selectively breeding for eons.
|
| Vulnerable monocultures; hyper-optimisation for a
| specific trait (or many breeds each optimised for a
| different trait); morphology significantly different to
| the wild form, with fashion preferences leading to
| fundamental health issues that can only be fixed by
| altering the fashion (GSD hip dysplasia, pug squashed
| noses).
| Brian_K_White wrote:
| Slaves that claim to like their slavery.
|
| People who have to buy RoundUp from Monsanto to keep
| breathing or to have kids etc.
|
| There is no limit to how bad this could go.
|
| And like pretty much any knowledge or technique, it will
| be developed and used, and so the only ways to head off
| the horror outcome is a combination of arbitrary legal
| declarations to just make some things illegal or at least
| pointless (not profitable), and open source, putting the
| same powers in the hands of individuals.
| mrexroad wrote:
| Space Seed and then, later, The Wrath of Khan.
| baybal2 wrote:
| > in the early 20th century that was influenced by North
| American culture that lingered well into the mid 20th
| century?[0]
|
| Unfortunately, it lingers well into the 21st one too.
|
| Bug eugenics foundations went through few rounds of
| rebrandings, and are still there influencing politics.
| sockpuppet69 wrote:
| twright0 wrote:
| My favorite line of reasoning about eugenics[0]: let's just
| accept that eugenics is a good thing; so good, in fact, we can
| go back in time and give a past society the ability to decide
| on the physical and mental attributes of their future, our
| present. Who would you pick? Would you go back 50, 100, 200,
| 500 years to gift this power?
|
| If you're uncomfortable with people several hundred years ago
| making decisions about your genetics, why should people several
| hundred years from now be comfortable with you making decisions
| about theirs?
|
| [0] https://www.smbc-comics.com/comic/eugenics-is-a-great-idea
| captainmuon wrote:
| I think one should be honest: Most people are more
| comfortable with making decisions for others, than with
| others making decisions for you. It's obvious! I think the
| ethical, "symmetric" stance is somewhat disingenuous.
|
| Similarly, I do not want the government to have certain
| powers. But I would happily award myself these powers if I
| were in charge, to be honest. I would never campaign for
| that, of course.
|
| This brings me to my argument against eugenics: I think in
| the _current world_ , it would have horrible effects. It
| would increase inequality, and create suffering. But that is
| not a neccessity. In another society, some elements of
| eugenics could be useful (to be clear: I'm not talking about
| deciding who can procreate and not, but for example
| preventing heritable diseases). The thing is, we can't agree
| on what this better society would look like. I of course
| believe that would be when I was in charge, but you'd
| probably disagree :-).
| XorNot wrote:
| The problem with eugenics is the coercive nature of it.
| People practice their own eugenics all the time - it's what
| we do when we engage in mate selection.
|
| Genetic engineering of offspring is a very different
| postulate to eugenics though - eugenics is trying to
| control people's reproductive choice towards an outcome
| desired by an external party, whereas genetic engineering
| would be parents trying to get desirable traits for their
| offspring.
|
| Technically I already did this when I had my first child:
| me and my wife got genetically tested for possible
| hereditary overlaps, as well as got as many screenings as
| were available when the child was developing.
|
| If those tests had shown risk factors, we would have picked
| IVF or other options to specifically knock out those traits
| from being passed on. If the technology to select a bunch
| of genes in my child that favored intelligence, or lower
| risks of lifestyle disease were available, you bet I
| would've paid a fair amount of money to get that done too.
| ncmncm wrote:
| We would breed them to be comfortable with our having made
| decisions about their genetics.
|
| Where by "we" I mean the plutocrats who make decisions about
| how each of us lives now, the Peter Thiels, the Vladimir
| Putins, the Xis, the Bill Gateses, the Kochs, the Morgans,
| the Stanleys, the Goldmans and the Sachses.
| TheOtherHobbes wrote:
| And since most of those people are kooks and/or
| narcissistic sociopaths, the results would be even more
| disastrous than where we are today.
| muzani wrote:
| If there's anything I've learned from software engineering,
| it's that ideas seem like good ideas until they're implemented.
| Something seems like a good gene to select for until 3
| generations later where someone else has to deal with it.
|
| The other thing that fascinates me is navel oranges. They're
| delicious, but they're sterile and come with defects (the
| navel). We're perfectly happy to deal with those defects
| because the benefits outweigh it. I wonder what defects come
| from radiation resistant supermen.
| jl6 wrote:
| Software engineering teaches us to identify defects and fix
| them, which is all fine and proper when you fully understand
| the root cause and the impact of the fix. But eugenic
| "fixing" of genetic "bugs" is more akin to deleting a whole
| module because you think it caused an error message. Maybe
| the error message goes away, but maybe you'll find out later
| that module was doing something useful after all.
| galaxyLogic wrote:
| I think it is that way, the output of genes is determined
| by what they do together, they all affect each other's
| function. This is possible because they evolved together
| and that is why they together are resilient against changes
| in the environment.. It is not like a program where
| flipping a single bit can crash the whole program.
| winrid wrote:
| If the universe has any humor, they'd have the side effect of
| emiting around 3.6 roentgens.
| Gatsky wrote:
| The technology to do this is... a long way away.
|
| It seems to me that human potential can be better realised in
| many ways, and eugenics is the way with probably the worst
| return on investment.
|
| For a start, we could try giving as many kids as possible in
| the world a decent crack at doing something important.
| Obviously this is very difficult and complicated. But then so
| is eugenics.
| naasking wrote:
| Eugenics isn't really that complicated. We've been doing it
| for millennia by selective breeding plants and animals.
| Direct genetic manipulation isn't the only form of eugenics.
| buryat wrote:
| The only conclusion we should make right now is that the Dyson
| Sphere doesn't exist and we're the only intelligent life in the
| Universe, which makes it all more terrifying.
| azernik wrote:
| Or that it does, and advanced civilizations just don't need
| that much energy.
| buryat wrote:
| evolution seems to be a constant fight for energy, this can
| be even expanded broadly: the universe is all about gathering
| energy. So not sure that someone would be fine with a
| constant limited energy supply. Plus those supplies
| eventually run out
| azernik wrote:
| Evolution is also a constant fight for food calories, and
| modern societies have escaped that struggle.
|
| Judging the dynamics of technological societies by those of
| evolving organisms is a common and extremely misleading
| trap.
| jl6 wrote:
| Perhaps civilizations with eternally increasing energy
| demands inevitably encounter a great filter of their own
| making, while civilizations that learn to live with more
| modest energy requirements live on in peace and silence.
| gfodor wrote:
| The second doesn't follow from the first. Dyson Spheres might
| just not be worth building.
| buryat wrote:
| agreed, but where do you get a lot of energy from? stars are
| the only answer seems like right now, nothing else
| produces/radiates energy in the universe in quantities needed
| ncmncm wrote:
| Anybody who can't fuse hydrogen and helium to produce as
| much energy as they can imagine using can hardly be
| considered civilized at all.
| ncmncm wrote:
| Dyson spheres (actually not spheres, in any sense,
| originally) were a clever idea, but it seems terribly
| parochial, not to say gooberish, to assume that anybody
| sophisticated enough to build such a thing would want one.
|
| More specifically, anybody sophisticated enough would
| dismantle their local gas giant and ice planets and convert
| them directly to energy, and leave the local daystar entirely
| out of the transaction.
|
| An advanced civilization will exist almost exclusively in the
| far outer reaches of a solar system, where the daystar
| provides nothing more than gravitation to keep the Kuiper
| belt organized. The most valuable resource for this advanced
| civilization will not be energy, which is cheap, or
| materials, which are cheaper, but cold. The abundunt cold out
| in the Kuiper Belt is essential to not being vaporized by the
| waste heat of the high energy processes more or less advanced
| civilizations cannot resist indulging in.
| buryat wrote:
| how do you disassemble a star? wouldn't you need a ton of
| energy to fight off the gravity?
|
| agreed that cooling might be something to look for
| therefore outer reaches are very tempting but then how do
| you deliver energy there?
| ncmncm wrote:
| Who suggested disassembling a star? You would burn your
| fingers. I stay well away from my star, and recommend it.
| buryat wrote:
| ah, I see, take a gas giant and put into fission through
| whatever process you want. Still seems like a lot of
| energy to go through until you can do fission while the
| star is right here
| jonathankoren wrote:
| I've been doing a lot of reading on megastructures, giant black
| hole powered computers, Von Neumann probes, and all the other
| super advanced technologies, and then thinking about the Fermi
| paradox, and I can't shake the feeling these are just gussied up
| magic by effectively godlike entities. They're completely
| impractical and take some pretty big hand waving to make them
| sound plausible.
|
| We're running out of excuses. We're either alone, or we're
| effectively alone ie everyone else is forever undetectable.
| Meaning they're more primitive, or stuck in some subterranean
| ocean or something. Either way, we're the Ancients sci-fi stories
| ale we ya talk about.
| xyproto wrote:
| Or everybody is hiding. Have you read The Three-Body Problem?
| jonathankoren wrote:
| You mean the books where magical aliens warp the fundamental
| constants of the universe to eliminate physical dimensions?
|
| Even if you skip past that to the underlying dark forest
| idea, it's an argument based on pure faith with zero evidence
| to support it. You need an all power malevolent society that
| works on a time scale of thousands if not millions of years,
| and then nit only eliminates another society for "reasons",
| but also then also perfectly covers up its own existence,
| because there may be some other bigger bad out there. It's
| about as convincing as the unicorn that's always right behind
| you, but everyone ignores because unicorns are super
| dangerous.
| prettyStandard wrote:
| I've been waiting to read this on Libby. I hope you didn't
| spoil it.
| xyproto wrote:
| No spoiler. The books are filled with events.
|
| They are well worth the read, IMO.
| ncmncm wrote:
| Space is big. Like, really big. The galaxy could have a million
| civilizations more powerful than you could imagine, and there
| is no reason why we would necessarily be able to see any of
| them.
|
| That assumes we would even be able to recognize one if we could
| see it.
| jonathankoren wrote:
| How are all powerful, but hidden entities, that live far
| away, but can kill us all in an instant, any different from
| the evidence for the invisible magical sky daddy?
|
| Even if I wanted to be generous, "really big" and "no reason
| why we would necessarily be able to see any of them" is
| indistinguishable from my statement of being "effectively
| alone".
| fullstackchris wrote:
| But why would they leave the same artifacts over and over
| again? Seems like a pretty boring existence for a "god". We've
| got blackholes, magnetars, pulsars, binary stars... and...
| that's about it... Seems much more likely these structures are
| the end result of some fixed set of physical rules than insane
| gods trapsing around the universe.
|
| Also agreeing with one of the comments above about how mind
| bogglingly massive space is, we've been effectively "listening"
| to space for only about 100 years, which creates an effective
| "listening sphere" of 4.188x10E6 light years^3, or 0.000524% of
| the milkyway's EIGHT TRILLION cubic lightyears in size (even if
| we could listen to all directions simultaneously, which we
| can't!)
|
| I mean, we've been listening to the Wow! area for 50 years now,
| which also hampers the kind of electromagnetic 'sweep' we could
| possible be doing in the meanwhile.
|
| My overall opinion is that it's just simple not been enough
| time of listening.
|
| Actually this idea seems quite interesting, it would be cool to
| do the calculus to figure out our effective "increase" in
| contact intersection as each consective second, minute, hour,
| day, and year goes by as we "listen" to space. Infinite
| overlapping spheres in an infinite 3D space... hmmmm
| jonathankoren wrote:
| What artifacts are they leaving? Literally nothing has EVER
| been detected.
|
| The reasons why they listen to the hydrogen line is because
| it's the most easiest to detect. However, the 50 year
| timeframe isn't really a problem. The entire sky has been
| measured multiple times in this 50 years, and nothing has
| been found. Unless you believe the signals passed 51 years
| ago, then the silence is deafening.
| awb wrote:
| > We're either alone, or we're effectively alone ie everyone
| else is forever undetectable.
|
| Native tribes could be forgiven for assuming they were alone
| until explorers and conquistadors arrived.
|
| It's possible that a civilization millions (or billions) of
| years ahead of us in biology, energy, philosophy, etc. is just
| beyond our comprehension at this moment to even know what to
| look for, where or how.
|
| Plus, we already try to make things hard to find like stealth
| fighters. Perhaps it's a good idea for survival in the universe
| to be difficult to find.
| jonathankoren wrote:
| Where's their waste heat? A pocket dimension? At some point
| you're just arguing for magic.
| [deleted]
| ordu wrote:
| It seems that Dyson sphere may be seen in infrared? So James Webb
| will find one, if they exist. We need just to wait a few years.
| ncmncm wrote:
| We already have infrared telescopes. There are literally
| billions of infrared sources already known in the immediate
| neighborhood. I promise you _none_ of them are Dyson spheres.
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