[HN Gopher] Eternity in six hours: Intergalactic spreading of in...
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Eternity in six hours: Intergalactic spreading of intelligent life
(2013)
Author : wallflower
Score : 49 points
Date : 2026-04-12 14:43 UTC (8 hours ago)
(HTM) web link (www.researchgate.net)
(TXT) w3m dump (www.researchgate.net)
| GTP wrote:
| This isn't my field, but I see a huge gap between what in the
| abstract they say it would be feasible for us and what we're
| currently capable of. I mean, we're able to send space probes
| around, but self-replicating space probes and Dyson spheres feel
| on another level. Am I the only one?
| sejje wrote:
| Do we have anything that self-replicates physically?
|
| Software, sure. I know 3D printer folks will sometimes 3D print
| parts for new machines. But nothing that fully replicates
| itself, right? Especially autonomously.
|
| Maybe we'll see what a moon base can bring us.
| GTP wrote:
| Additionally, you also have to consider that a self-
| replicating space probe should be able to find, retrieve, and
| process the raw materials needed to build new probes on its
| own. A 3D printer can print some of its own parts, but with
| externally-provided material that it isn't able to produce on
| its own.
| diziet wrote:
| Basically all of life is self replicating, physically.
| psychoslave wrote:
| I guess the OP meant something that is more flatous for
| human vanity to feel like a demiurge when at most it would
| be a tool of cosmos in its experiment.
| GTP wrote:
| Yes, but this isn't what the paper is talking about.
| NitpickLawyer wrote:
| > what we're currently capable of.
|
| What we're capable of != what we're doing / not doing because
| of political will. We are technically capable of reaching
| significant fractions of c with tech from the 1960s. We'll
| never do that because there's no will to do it, but the tech is
| there.
|
| Same for self replicating stuff. We could build self-contained
| factories that build stuff from raw minerals, but we'll likely
| not do it until there's a will for it. Or need for it.
| TheOtherHobbes wrote:
| Political will is part of the Fermi paradox. So are technical
| reliability and cultural stability.
|
| The idea that you can just build a thing and send out a swarm
| and (slow) boom - you've colonised the galaxy, and all the
| adjacent galaxies - is hopelessly naive. To the point I'd
| call it stupid and silly.
|
| Let's say you have a replicator thing that works. You send
| them out in swarms.
|
| And then what? Some die, some miss, some are destroyed by
| accidents.
|
| Some work.
|
| But "a replicator landed and made some more" is not
| _colonisation._ Colonisation implies there 's some kind of
| to-and-fro traffic, maybe trade, some kind of information
| exchange at a minimum.
|
| And that implies the source civilisation has political,
| technological, and cultural stability, which can survive an
| incredibly slow diaspora.
|
| Colonisation worked on Earth because it didn't take long to
| cross the Atlantic by sailing ship. Successful colonisers
| landed where humans already existed and trade was easy.
|
| It doesn't work on interstellar, never mind intergalactic
| time scales, because _nothing stays stable for that long._
| Not hardware, software, politics, or culture.
|
| Nor, on slightly longer periods, biology. On much longer
| periods, geology, and eventually astrophysics, because stars
| change, and planetary systems aren't unconditionally stable.
|
| So a colonising wave from a unified culture is an incredibly
| unlikely thing, not at all an obvious necessity.
| GTP wrote:
| This would mean bootstrapping current advanced manufacturing
| technologies to a new planet. You would need so many
| different tools to do that that I seriously doubt we are
| currently capable of making it compact enough to be sent into
| deep space with current technologies. We're currently sending
| at most small capsules into deep space, my gut tells me that
| for self-contained factories we would need to send something
| in the size order of a skyscraper.
| mullingitover wrote:
| Life itself could arguably be a Von Neumann probe. It's so good
| at spreading that it's a _problem_ , when we send probes to
| other bodies in our own solar system we often sanitize them
| because we worry life will hitch a ride and start colonizing.
|
| Life on a planet is a lot like a continuous fire, fires often
| send out embers that start new fires elsewhere.
|
| You send out little packets of life to new places, wait single-
| digit billions of years (a blink of an eye for the universe,
| really), boom: new intelligent species with potential to shoot
| more seeds out into the universe.
| gmuslera wrote:
| "And with this papyrus, we conclude that in five thousand years,
| mankind will finally build a staircase to the Moon"
| fogof wrote:
| I recently saw an interesting criticism of this paper: That by
| the end stages of the disassembly of Mercury, the amount of heat
| generated would be so much as to melt the surface, calling into
| question whether the mass driver system could work at such a high
| rate.
| Sharlin wrote:
| Refreshing to see a _technical_ criticism of this paper for a
| change.
| restalis wrote:
| In the open space, shades get very cold, like a few degrees
| over absolute zero cold, because even without a medium to
| facilitate convection and (atmospheric contact) conduction, the
| loss of heat through mere radiation (into the pitch black
| universe) is very efficient (for normal, non-reflective
| materials). Thus, for an astral body to remain in a melted
| state, continuous steams of energy should be poured in (and
| some thermo-insulating gaseous atmosphere may also help to
| reduce cooling, if the body in question would have enough
| gravity to retain it), but that's hardly a thing to worry for a
| project where the energy itself is carefully controlled and
| dosed.
| V__ wrote:
| Has someone answered why a civilization would send "von Neumann
| probes" or similar into space? It would take so long for any
| answers from those probes to arrive that there really doesn't
| seem much value in them.
| soraki_soladead wrote:
| We don't know however "It would take so long" is an
| anthropomorphic assumption of time scale.
| qingcharles wrote:
| Right. We have no idea how another species perceives time.
| This could be nothing to them.
|
| And even if they do perceive it like us, that hasn't stopped
| humans from great projects. How many generations did it take
| to complete Stonehenge or the Great Wall of China? We're
| still on top of Voyager too after 50 years.
| bryanrasmussen wrote:
| of course by the time we had the ability to do von Neumann
| Probes our anthropomorphic assumption of time scales may have
| changed.
|
| How much would human life span need to increase for a von
| Neumann Probe to seem reasonable. I would think a life span
| of 600 and you're thinking, sure I won't get to see it
| through, but my allotted genetic offspring that I am allowed
| at age 500 if either of my other two have failed might.
| rolph wrote:
| requirements change with purpose.
|
| a "kilroy was here" sign has different purpose than "eat at
| joes".
|
| is it enough to say "hi, your not alone" ? would we
| actually want to encourage discourse, or visitation.
| fc417fc802 wrote:
| If you expect to live past a few hundred years it isn't
| clear why your lifespan wouldn't be indefinite. The
| prerequisites for achieving the former appear to be more or
| less the same as those of the latter.
| anbende wrote:
| Well, if you personally were building von Neumann machines do
| any purpose in the solar system, would YOU be interested in
| sending some to neighboring systems knowing that you could
| conceivably get a response in your lifetime.
|
| Would you be at all interested in expanding that project to
| outlast you?
|
| And even if you personally wouldn't be so inclined, surely you
| know or have met people who might?
|
| Once you have the self replication, expanding scope may just be
| additional code...
| loandbehold wrote:
| You can ask same question about any decision that outlasts you.
| E.g. why write a will for your children?
| canjobear wrote:
| Some will do it, some won't. The ones that do will be
| overrepresented in the universe.
| krapp wrote:
| An odd assertion to make, given that apparently no one has
| done it.
| jerf wrote:
| To build more computronium than you can in your own system,
| assuming the demand for that will always rise.
| fizx wrote:
| Sure, but you then can't access the computronium, because
| communication is so bad.
|
| Also, I wonder if good old-fashioned computing is interesting
| at all to a civilization that's had access to advanced AI and
| quantum computing for a while.
|
| Like we haven't really figured out how to get an ML model to
| run on a quantum computer, or how to build a quantum-native
| computer (i.e. surface of a black hole, or some other way
| that doesn't rely on our current sense of quantum error
| correction), but I don't know of any physical laws that
| preclude it.
|
| I'd bet if aliens invaded our galaxy, they'd go for the super
| black holes in the center, or some other resource beyond our
| use and understanding, not this random water planet on the
| edge.
| abetusk wrote:
| If we're talking about civilizations that have access to energy
| that's on the order of many stars, the civilization itself can
| be considered a meta-organism that spans many millennia.
| Launching probes that take hundreds or thousands of years to
| report back becomes a small fraction of overall lifespan.
| Sharlin wrote:
| There are no answers expected. This is a colonization wave.
| satisfice wrote:
| Can we have a science paper that explains why we can colonize
| Andromeda but we can't build high speed rail?
| psychoslave wrote:
| Because we don't refer to the same entities in each case?
| fnord77 wrote:
| There's no NIMBYs in Andromeda
| hgoel wrote:
| In one case "we" is an imaginary humanity as a whole acting to
| fulfill a grand species defining mission, in the other case
| "we" is the real, decadent, ignorant and divided population of
| some countries.
| gcanyon wrote:
| No humans go, no information returns.
|
| Sending an acorn-sized probe to another galaxy to make more
| acorn-sized probes: what even is the point of that? To make
| _very_ slow grey goo a reality?
|
| If actual humans find a way to go to Andromeda (other than
| waiting for it to arrive, heh) and want to, good for them.
| Otherwise we should actively discourage anything like the project
| proposed
| Sharlin wrote:
| This is a study of the _feasibility_ of launching an
| intergalactic colonization wave (and its implications re: the
| Fermi paradox), not a proposal that humans should do that (it
| would be just slightly ahead of its time for that!), or a
| discussion of the ethics or higher-level utility of doing so.
| It would be refreshing to see someone discuss the things paper
| actually discusses. To use early-2000s terminology, the paper
| 's _future shock level_ is higher than that of most HN readers,
| leading to rather banal discourse.
|
| In any case, I'm fairly sure the authors agree that sending
| mindless automata to colonize the universe doesn't seem like a
| great idea. Nevertheless some alien intelligence (including an
| Earth-based AGI) might find it a completely reasonable, even
| _imperative_ , goal.
|
| But sentient machines or uploads (assuming for the sake of this
| this thought experiment that they are possible)? That's a
| different thing.
| polotics wrote:
| Is there already a name for that effect where grandiose plans
| somehow appear to be more feasible than the simple mundane step-
| by-step issues resolution that even though they clearly stand in
| the way of said grand plans, are not worth investing thought and
| effort in?
|
| When it comes to software projects my pet-name for it is the
| "big-bang theory", but in the article's domain that's kind of
| already taken.
| hollerith wrote:
| "Far-mode thinking".
|
| https://www.lesswrong.com/w/near-far-thinking
| jerf wrote:
| I use the term "30,000 foot view" a lot:
| https://nanoglobals.com/glossary/30000-foot-view/
|
| It appeals to me because if you've ever taken a flight you can
| see how the details get progressively erased as you lift.
| Details that matter for a lot of reasons even if you can't see
| them.
| zackmorris wrote:
| In his 1999 book "Entering Space: Creating a Spacefaring
| Civilization", Robert Zubrin mentioned checking the math for
| Bussard ramjets with Dana Andrews in their 1988 join paper
| "Magnetic Sails and Interstellar Travel" and found that they
| aren't capable of reaching more than a few percent of the speed
| of light before drag overcomes propulsion:
|
| https://www.goodreads.com/book/show/54728.Entering_Space
|
| https://www.researchgate.net/publication/236447908_Magnetic_...
|
| That's not to say that they don't work. But they'll probably be
| used primarily for braking to enter orbit around destination
| stars.
|
| Probably the only way to reach a high fraction of the speed of
| light is to construct a giant laser to beam energy to a spaceship
| (which uses a reflector to receive light pressure momentum) and
| leave it behind orbiting the origin star. That's the premise of
| the Breakthrough Starshot project, which is ambitious with
| today's technology. But with self-replicating makerbots, building
| one may not be a big deal.
|
| https://en.wikipedia.org/wiki/Breakthrough_Starshot
|
| Unfortunately the force of light pressure (by F=2P/c for full
| reflection) is only about 2/3 of a kg or 1.5 lbs per GW, so a TW
| or greater would be needed for practical thrust. However, light
| pressure becomes the most efficient form of propulsion above
| about 25% to 50% c, if fusion or antimatter is used to create a
| gamma ray rocket.
|
| Personally, I find it unlikely that aliens use these methods. I
| think that they probably worked out how to build neutrino lasers,
| since they don't burn up objects in their wake, perhaps by
| scaling superradiant Bose Einstein condensates:
|
| https://arxiv.org/abs/2412.11765
|
| In embarrassingly oversimplified layman's terms, I think that
| works by recruiting the macro-scale quantum state of the
| condensate (increased cross-section or barn) to overcome the
| short interaction distance of the weak force. Or by cooling the
| atoms to such an extent that they don't have the energy to hold
| themselves apart anymore, which accelerates their decay. I'm sure
| my explanations are wrong somehow.
|
| Soon we may be able to investigate stuff like gravity waves and
| how the fabric of spacetime may be able to rebound above flat to
| create tiny ripples that allow mass energy to escape black holes,
| for example. I know that current theories don't state it quite
| that way, but if we consider stuff like the no-hair theorem and
| black box thought experiments, it's hard to see how Hawking
| radiation could exist without the wavelike nature of spacetime.
| We can even experiment with it on a relatively large scale by
| measuring the Casimir force. If we can rebound space, then we can
| play with stuff like negative energy and Alcubierre drives.
|
| I looked up a Dyson sphere made from Mercury and it would be 1.5
| mm thick, so aliens almost certainly aren't building them. But
| Dyson rings and swarms are probably a thing.
|
| Some people in the tinfoil hat crowd think that UFOs can move 4th
| dimensionally and just travel orthogonally to our space and
| appear somewhere else. Theoretically, that might only require the
| energy difference (delta v) between planets. That hinges on if
| gravity spans higher dimensions and also touches on the
| multiverse. I'm way outside my wheelhouse so I'll stop blabbering
| about that.
|
| In all honesty though, I question whether aliens travel. I think
| civilizations ascend about 10 years after they implement AI, or
| annihilate themselves in a Great Filter, their equivalent of
| WWIII. We're already staring the secrets of the universe in the
| face with automated theorem provers. And FUD around that and
| other accelerating tech drives people to become Luddites and
| elect amoral people who would gladly see the world burn for
| profit. So things could go either way really.
|
| In my heart, I feel like we have a childlike understanding of
| consciousness. It probably transcends 4D spacetime. It's not hard
| to imagine aliens scaling what was learned from the CIA Gateway
| Program and doing stuff like FTL message passing via remote
| viewing. At that point FTL teleportation comes into the realm of
| possibility, sort of like in Dune.
|
| If so, then aliens are probably everywhere, know about us, and
| maybe had a hand in our evolution. The probably live in what we
| think of as a Matrix, where years could go by for every second of
| our time. Another interpretation might be that they're able to
| return to source consciousness and exist as one, rather than in
| separation like we do. Maybe they periodically choose to
| reincarnate in us to study what transitioning to a spacefaring
| civilization looks like.
|
| I probably shouldn't have bothered writing all of this, but it's
| Sunday, and I also really don't want to do my taxes.
| ilitirit wrote:
| The concept of "Dyson spheres" was a joke by Freeman Dyson. It
| was never meant to be taken seriously. There's a clip about this
| floating around somewhere in which he finds it funny that the
| thing he's most well-known for was not even a serious paper. Dr.
| Angela Collier did a video about it.
|
| https://www.youtube.com/watch?v=fLzEX1TPBFM
| testaccount28 wrote:
| is there anything Collier doesn't sneer at? her purpose seems
| to be discouraging free and creative thinking.
| jmyeet wrote:
| The only person who seems to claim that Dyson Spheres were a
| "joke" is Angela Collier and people quoting her. I've seen no
| other source for this claim.
|
| But even if it's true, which I don't think it is, it doesn't
| matter. Why? Because the idea is actually sound and a lot of
| thought has gone into it by people who have backgrounds in
| physics and engineering.
|
| It's worth adding that "Dyson Swarm" is the more common
| nomenclature now because of a mistaken belief that a Dyson
| sphere was a rigid spherical shell you build around a star.
| That was never the case and there's no even theorized material
| that could support this kind of rigid structure. It was always
| a cloud of small orbitals so the "Dyson Swarm" should alleviate
| any confusion (hopefully).
|
| Our civilization is ultimately energy-limited. I've seen
| estimates that we use ~10^11 Watts of energy. The Sun's entire
| output is ~10^25 Watts. That's a truly staggering amount of
| energy. We can barely comprehend what might be possible with
| that much energy. But one of those things is interstellar
| travel.
|
| Many discussions on interstellar travel gloss over just how
| large the energy budgets are. But propelling objects with solar
| sails, particularly if you concentrate energy, seems feasible.
| At least the physics holds up.
|
| Spreading throughout the galaxy becomes an almost inevitable
| consequence once you have the capability to do so.
| api wrote:
| When you zoom this far out, anything can look possible... or
| impossible.
|
| This is the same fallacy, but taken toward rather than away from
| infinite possibility, that underlies things like the Club of
| Rome's world models and their limits to growth thesis.
|
| Zoom way out and the details disappear. Look only at aggregate
| statistics and extrapolate. Do this and you tend to get graphs
| that go to infinity (this paper) or to zero (limits to growth).
|
| But the details are where things actually happen.
|
| Also look up computational irreducibility, which is kind of
| another way of approaching what I'm getting at here. You can only
| treat details in aggregate for systems whose causality is
| strictly hierarchical. If one detail can change the whole system,
| every detail must be considered or a simulation is invalid.
|
| Turns out that living systems are like this.
| Peritract wrote:
| Over the past 163 years, our capacity for eternity has decreased
| by a factor of six [0].
|
| [0] https://www.poetryfoundation.org/poems/43650/auguries-of-
| inn...
| TheTaytay wrote:
| Are there any serious papers or theories that postulate that DNA
| is the self replicating matter sent to colonize the galaxy? It
| appears to be quite adaptable to its environment and able to hold
| a surprising amount of encoded information.
| hermitcrab wrote:
| >intergalactic colonisation is not far beyond our current
| capabilities today.
|
| That is a ridiculous thing to say. We can barely get to the moon
| today.
| hermitcrab wrote:
| So a probe travelling between galaxies at 99%c can't hit anything
| bigger than 1.46x10-12 kg? It is ~2.5 million light-years between
| us and Andromeda. I don't know how much matter there is between
| the galaxies (does anyone?). But travelling that sort of distance
| without hitting anything above that tiny mass seems very
| unlikely. Also how is your tiny robot probe supposed to power any
| guidance or maintenance systems for that sort of duration of
| trip?
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