“Close to the speed of light” has to be quite close to the speed of light for that argument to hold (at 0.8c about half of the volume in the light cone of an expanding civilization is outside of that civilization’s expansion front).
It doesn’t really need to be that fast, provided that the expansion front is deep. Seed probes that act as a nucleus for construction could be almost impossible to see, and the parent civilization might be very distant.
Even if the parent civilization did megaengineering of a galaxy (e.g. enclosing all the stars in Dyson swarms or outright disassembling them), we’d probably see that as a natural phenomenon. We can’t tell what would otherwise have been there instead, and such large-scale changes probably do still take a long time to carry out even with advanced technology.
There are in fact a great many observations in astronomy where we don’t really know what’s happening. Obviously nobody is claiming “aliens did it”, especially after the pulsar debacle last century. There are moderately plausible natural hypotheses. But if aliens were doing it, we probably couldn’t conclusively say so.
Yes, it does have to be fast IMO, but I think fast expansion (at least among civilizations that decide to expand much at all) is very likely.
Of course the first few starships that a civilization sends to colonize the nearest stars will probably not be going anywhere near the speed of light. (Unless it really is a paperclips-style superintelligence, perhaps.) But within a million years or so, even with relatively slow-moving ships, you have colonized thousands of solar systems, built dyson swarms around every star, have a total population in the bajilions, and have probably developed about all the technology that it is physically possible to develop. So, at some point it’s plausible that you start going very close to the speed of light, because you’ll certainly have enough energy + technology to do so, and because it might be desirable for a variety of reasons:
- Maybe we are trying to maximize some maximizable utility function, be that paperclips or some more human notion, and want to minimize what Nick Bostrom calls “astronomical waste”. - Maybe we fail to coordinate (via a strong central government or etc), and the race to colonize the galaxy becomes a free-for-all, rewarding the fastest and most rapacious settlers, a la Robin Hanson’s “Burning the cosmic commons”.
Per your own comment—if you only colonize at 0.8c so your ships can conserve energy, you are probably actually missing out on lots and lots of energy, since you will only be able to harvest resources from about half the volume that you could grab if you traveled at closer to lightspeed!
Maybe, but I have to also put this all in a somewhat different frame. Is the universe populated by birds or mice? Are the resources nice ground full or worms or perhaps dangerous traps with the cheese we want?
So if we’re birds and the universe resources are worms, maybe a race. If we’re all mice and resources are those dangerous traps with cheese, well, the old saying “The early bird might get the worm but the second mouse gets the cheese.” In a universe populated by mice & cheese, civilation expansion may well be much slower and measured.
Perhpas we can add one of the thoughts from the Three Body Problem series—advertising your civilation in the universe might be a sure way to kill yourself. Possibly fits with the Grabby Aliens thought but would argue for a different type of expansion patter I would think.
That, and I’m not sure how the apparent solution ot energy problems (apparenly a civilization has no engery problem so accelleration and decellerations costs don’t really matter) impacts a desire for additional resources. And if the energy problem is not solved then we need to know the cost curves for accelleration and decelleration to optimize speed in that resource search/grab.
What kinds of space resources are like “mice & cheese”? I am picturing civilizations expanding to new star systems mostly for the matter and energy (turn asteroids & planets into a dyson swarm of orbiting solar panels and supercomputers on which to run trillions of emulated minds, plus constructing new probes to send onwards to new star systems).
re: the Three Body Problem books—I think the book series imagines that alien life is much, much more common (ie, many civilizations per galaxy) than Robin Hanson imagines in his Grabby Aliens hypothesis, such that there are often new, not-yet-technologically-mature civilizations popping up nearby each other, around the same time as each other. Versus an important part of the Grabby Aliens model is the idea that the evolution of complex life is actually spectacularly rare (which makes humans seem to have evolved extremely early relative to when you might expect, which is odd, but which is then explained by some anthropic reasoning related to the expanding grabby civilizations—all new civilizations arise “early”, because by the mid-game, everything has been colonized already). If you think that the evolution of complex life on other planets is actually a very common occurrence, then there is no particular reason to put much weight on the Grabby Aliens hypothesis.
In The Three Body Problem, Earth would be wise to keep quiet so that the Trisolarians don’t overheard our radio transmissions and try to come and take our nice temperate planet, with its nice regular pattern of seasons. But there is nothing Earth could do about an oncoming “grabby” civilization—the grabby civilization is already speeding towards Earth at near-lightspeed, and wants to colonize every solar system (inhabited and uninhabited, temperate planets with regular seasons or no, etc), since it doesn’t care about temperate continents, just raw matter that it can use to create dyson swarms. The grabby civilizations are already expanding as fast as possible in every direciton, coming for every star—so there is no point trying to “hide” from them.
Energy balance situation: - the sun continually emits around 10^26 watts of light/heat/radiation/etc. - per some relativity math at this forum comment, it takes around 10^18 joules to accelerate 1kg to 0.99c - so, using just one second of the sun’s energy emissions, you could afford to accelerate around 10^8 kg (about the mass of very large cargo ships, and of the RMS Titanic) to 0.99c. Or if you spend 100 days’ worth of solar energy instead of one second, you could accelerate about 10^15 kg, the mass of Mt. Everest, to 0.99c. - of course then you have to slow down on the other end, which will take a lot of energy, so the final size of the von neumann probe that you can deliver to the target solar system will have to be much smaller than the Titanic or Mt Everest or whatever. - if you go slower, at 0.8c, you can launch 10x as much mass with the same energy (and you don’t have to slow down as much on the other end, so maybe your final probe is 100x bigger), but of course you arrive more slowly—if you’re travelling 10 light years, you show up 1.9 years later than the 0.99c probe. If you’re travelling 100 light years, you show up 19 years later. - which can colonize the solar system and build a dyson swarm faster—a tiny probe that arrives as soon as possible, or a 100x larger probe that arrives with a couple years’ delay? this is an open question that depends on how fast your von neuman machine can construct solar panels, automated factories, etc. Carl Shulman in a recent 80K podcast figures that a fully-automated economy pushing up against physical limits, could double itself at least as quickly as once per year. So mabye the 0.99c probe would do better over the 100 light-year distance (arriving 19 years early gives time for 19 doublings!), but not for the 10 light-year distance (the 0.99c probe would only have doubled itself twice, to 4x its initial mass, by the time the 0.8c probe shows up with 100x as much mass) - IMO, if you are trying to rapaciously grab the universe as fast as possible (for the ultimate purpose of maximizing paperclips or whatever), probably you don’t hop from nearby star to nearby star at efficient speeds like 0.8c, waiting to set up a whole new dyson sphere (which probably takes many years) at each stop. Rather, your already-completed dyson swarms are kept busy launching new probes all the time, targeting ever-more-distant stars. By the time a new dyson swarm gets finished, all the nearby stars have also been visited by probes, and are already constructing dyson swarms of their own. So you have to fire your probes not at the nearest stars, but at stars some distance further away. My intuition is that the optimal way to grab the most energy would end up favoring very fast expansion speeds, but I’m not sure. (Maybe the edge of your cosmic empire expands at 0.99c, and then you “mop up” some interior stars at more efficient speeds? But every second that you delay in capturing a star, that’s a whopping 10^26 joules of energy lost!)
After even the first million years as slow as 0.1c, the galaxy is full and it’s time to go intergalactic. A million years is nothing in the scale of the universe’s age.
When sending a probe millions of light years to other galaxies, the expense of 0.999c probes start to look more useful than 0.8c ones, saving hundreds of thousands of years. Chances are that it wouldn’t just be one probe either, but billions of them seeding each galaxy within plausible reach.
Though as with any discussion about these sorts of things, we have no idea what we don’t know about what a civilization a million years old might achieve. Discussions of relativistic probes are probably even more laughably primitive than those of using swan’s wings to fly to the abode of the Gods.
“Close to the speed of light” has to be quite close to the speed of light for that argument to hold (at 0.8c about half of the volume in the light cone of an expanding civilization is outside of that civilization’s expansion front).
It doesn’t really need to be that fast, provided that the expansion front is deep. Seed probes that act as a nucleus for construction could be almost impossible to see, and the parent civilization might be very distant.
Even if the parent civilization did megaengineering of a galaxy (e.g. enclosing all the stars in Dyson swarms or outright disassembling them), we’d probably see that as a natural phenomenon. We can’t tell what would otherwise have been there instead, and such large-scale changes probably do still take a long time to carry out even with advanced technology.
There are in fact a great many observations in astronomy where we don’t really know what’s happening. Obviously nobody is claiming “aliens did it”, especially after the pulsar debacle last century. There are moderately plausible natural hypotheses. But if aliens were doing it, we probably couldn’t conclusively say so.
Yes, it does have to be fast IMO, but I think fast expansion (at least among civilizations that decide to expand much at all) is very likely.
Of course the first few starships that a civilization sends to colonize the nearest stars will probably not be going anywhere near the speed of light. (Unless it really is a paperclips-style superintelligence, perhaps.) But within a million years or so, even with relatively slow-moving ships, you have colonized thousands of solar systems, built dyson swarms around every star, have a total population in the bajilions, and have probably developed about all the technology that it is physically possible to develop. So, at some point it’s plausible that you start going very close to the speed of light, because you’ll certainly have enough energy + technology to do so, and because it might be desirable for a variety of reasons:
- Maybe we are trying to maximize some maximizable utility function, be that paperclips or some more human notion, and want to minimize what Nick Bostrom calls “astronomical waste”.
- Maybe we fail to coordinate (via a strong central government or etc), and the race to colonize the galaxy becomes a free-for-all, rewarding the fastest and most rapacious settlers, a la Robin Hanson’s “Burning the cosmic commons”.
Per your own comment—if you only colonize at 0.8c so your ships can conserve energy, you are probably actually missing out on lots and lots of energy, since you will only be able to harvest resources from about half the volume that you could grab if you traveled at closer to lightspeed!
Maybe, but I have to also put this all in a somewhat different frame. Is the universe populated by birds or mice? Are the resources nice ground full or worms or perhaps dangerous traps with the cheese we want?
So if we’re birds and the universe resources are worms, maybe a race. If we’re all mice and resources are those dangerous traps with cheese, well, the old saying “The early bird might get the worm but the second mouse gets the cheese.” In a universe populated by mice & cheese, civilation expansion may well be much slower and measured.
Perhpas we can add one of the thoughts from the Three Body Problem series—advertising your civilation in the universe might be a sure way to kill yourself. Possibly fits with the Grabby Aliens thought but would argue for a different type of expansion patter I would think.
That, and I’m not sure how the apparent solution ot energy problems (apparenly a civilization has no engery problem so accelleration and decellerations costs don’t really matter) impacts a desire for additional resources. And if the energy problem is not solved then we need to know the cost curves for accelleration and decelleration to optimize speed in that resource search/grab.
What kinds of space resources are like “mice & cheese”? I am picturing civilizations expanding to new star systems mostly for the matter and energy (turn asteroids & planets into a dyson swarm of orbiting solar panels and supercomputers on which to run trillions of emulated minds, plus constructing new probes to send onwards to new star systems).
re: the Three Body Problem books—I think the book series imagines that alien life is much, much more common (ie, many civilizations per galaxy) than Robin Hanson imagines in his Grabby Aliens hypothesis, such that there are often new, not-yet-technologically-mature civilizations popping up nearby each other, around the same time as each other. Versus an important part of the Grabby Aliens model is the idea that the evolution of complex life is actually spectacularly rare (which makes humans seem to have evolved extremely early relative to when you might expect, which is odd, but which is then explained by some anthropic reasoning related to the expanding grabby civilizations—all new civilizations arise “early”, because by the mid-game, everything has been colonized already). If you think that the evolution of complex life on other planets is actually a very common occurrence, then there is no particular reason to put much weight on the Grabby Aliens hypothesis.
In The Three Body Problem, Earth would be wise to keep quiet so that the Trisolarians don’t overheard our radio transmissions and try to come and take our nice temperate planet, with its nice regular pattern of seasons. But there is nothing Earth could do about an oncoming “grabby” civilization—the grabby civilization is already speeding towards Earth at near-lightspeed, and wants to colonize every solar system (inhabited and uninhabited, temperate planets with regular seasons or no, etc), since it doesn’t care about temperate continents, just raw matter that it can use to create dyson swarms. The grabby civilizations are already expanding as fast as possible in every direciton, coming for every star—so there is no point trying to “hide” from them.
Energy balance situation:
- the sun continually emits around 10^26 watts of light/heat/radiation/etc.
- per some relativity math at this forum comment, it takes around 10^18 joules to accelerate 1kg to 0.99c
- so, using just one second of the sun’s energy emissions, you could afford to accelerate around 10^8 kg (about the mass of very large cargo ships, and of the RMS Titanic) to 0.99c. Or if you spend 100 days’ worth of solar energy instead of one second, you could accelerate about 10^15 kg, the mass of Mt. Everest, to 0.99c.
- of course then you have to slow down on the other end, which will take a lot of energy, so the final size of the von neumann probe that you can deliver to the target solar system will have to be much smaller than the Titanic or Mt Everest or whatever.
- if you go slower, at 0.8c, you can launch 10x as much mass with the same energy (and you don’t have to slow down as much on the other end, so maybe your final probe is 100x bigger), but of course you arrive more slowly—if you’re travelling 10 light years, you show up 1.9 years later than the 0.99c probe. If you’re travelling 100 light years, you show up 19 years later.
- which can colonize the solar system and build a dyson swarm faster—a tiny probe that arrives as soon as possible, or a 100x larger probe that arrives with a couple years’ delay? this is an open question that depends on how fast your von neuman machine can construct solar panels, automated factories, etc. Carl Shulman in a recent 80K podcast figures that a fully-automated economy pushing up against physical limits, could double itself at least as quickly as once per year. So mabye the 0.99c probe would do better over the 100 light-year distance (arriving 19 years early gives time for 19 doublings!), but not for the 10 light-year distance (the 0.99c probe would only have doubled itself twice, to 4x its initial mass, by the time the 0.8c probe shows up with 100x as much mass)
- IMO, if you are trying to rapaciously grab the universe as fast as possible (for the ultimate purpose of maximizing paperclips or whatever), probably you don’t hop from nearby star to nearby star at efficient speeds like 0.8c, waiting to set up a whole new dyson sphere (which probably takes many years) at each stop. Rather, your already-completed dyson swarms are kept busy launching new probes all the time, targeting ever-more-distant stars. By the time a new dyson swarm gets finished, all the nearby stars have also been visited by probes, and are already constructing dyson swarms of their own. So you have to fire your probes not at the nearest stars, but at stars some distance further away. My intuition is that the optimal way to grab the most energy would end up favoring very fast expansion speeds, but I’m not sure. (Maybe the edge of your cosmic empire expands at 0.99c, and then you “mop up” some interior stars at more efficient speeds? But every second that you delay in capturing a star, that’s a whopping 10^26 joules of energy lost!)
After even the first million years as slow as 0.1c, the galaxy is full and it’s time to go intergalactic. A million years is nothing in the scale of the universe’s age.
When sending a probe millions of light years to other galaxies, the expense of 0.999c probes start to look more useful than 0.8c ones, saving hundreds of thousands of years. Chances are that it wouldn’t just be one probe either, but billions of them seeding each galaxy within plausible reach.
Though as with any discussion about these sorts of things, we have no idea what we don’t know about what a civilization a million years old might achieve. Discussions of relativistic probes are probably even more laughably primitive than those of using swan’s wings to fly to the abode of the Gods.