What would we expect to see in terms of signals from eg, Andromeda if alien life arose there 100 million years ago and is currently inhabiting almost all of it, assuming they weren’t deliberately sending signals to us?
Well, the most obvious thing is we’d probably see signs that stars are being used. For example if a sizeable fraction of the stars in Andromeda had Dyson spheres, or had stellar lifting, we’d be able to see that from here because the star’s profiles would look different. For example, in the case of a Dyson sphere we’d expect to see much more of the radiation in the infrared range . In fact, if one has Dysoned a large fraction of the stars of a galaxy, we should be able to notice this for galaxies orders of magnitude farther away than Andromeda.
Well, the most obvious thing is we’d probably see signs that stars are being used.
Why?
I mean, I get the assumption here—that we’ve experienced a geometric surge in energy use, economic growth and several other things as a result of the Industrial Revolution, and it hasn’t disappeared yet—but it seems like a potentially important one to question. What would you expect to see if you’re wrong, if the Cold War-era visions of high-energy, superadvanced civilizations or their Singularitarian cousins, the visions of superpowerful AGI and/or uploaded humans are based on the assumption things won’t regress to the mean?
What would you ever see from Andromeda, in that case? Hell, what would you even see from Alpha Centauri if that were the case?
That’s a good point. It is possible that the problem is that large scale engineering projects and the like simply don’t happen. And if that’s the case then it may be that things would look very similar to what we see. In a similar vein, there may be some as yet undiscovered loophole or exception to the laws of thermodynamics that makes harvesting stars unnecessary (this seems unlikely). But not all of these things are purely about energy consumption. While a Dyson sphere or ringworld is nice from an energy standpoint, they also provide living space for growing populations. Yes, it could be that populations simply level off (and Japan and Western Europe do show that that can happen). But at this point we need to now have a lot of assumptions about what every intelligence species does. If only a small fraction try to harvest a lot of energy and only a small fraction don’t control their population growth, then one would expect to probably see something. The idea that not a single species out there tries these sorts of things seems about as surprising as there simply not being anyone out there to do it.
But at this point we need to now have a lot of assumptions about what every intelligence species does.
Not so—you only need to posit that sustained growth spurts like the one we’re living through are anomalies, and subject to some rather significant limits.
The essay you linked to is essentially focused on what happens if you stay at a single star. If anything, it should be an argument as to why to expect things to spread out: having a lot more planets and stars means one has a lot more energy at one’s disposal.
But the chief limitation in the preceding analysis is Earth’s surface area—pleasant as it is. We only gain 16 years by collecting the extra 30% of energy immediately bouncing away, so the great expense of placing an Earth-encircling photovoltaic array in space is surely not worth the effort. But why confine ourselves to the Earth, once in space? Let’s think big: surround the sun with solar panels. And while we’re at it, let’s again make them 100% efficient. Never-mind the fact that a 4 mm-thick structure surrounding the sun at the distance of Earth’s orbit would require one Earth’s worth of materials—and specialized materials at that. Doing so allows us to continue 2.3% annual energy growth for 1350 years from the present time.
At this point you may realize that our sun is not the only star in the galaxy. The Milky Way galaxy hosts about 100 billion stars. Lots of energy just spewing into space, there for the taking. Recall that each factor of ten takes us 100 years down the road. One-hundred billion is eleven factors of ten, so 1100 additional years. Thus in about 2500 years from now, we would be using a large galaxy’s worth of energy.
In other words, keep up the paltry growth rate listed at the start of the essay, and take the fantastically-favorable assumptions that go with it (like 100% efficiency) and you find that even if we’re surrounding every star in Dyson spheres we can’t keep up with growth, because within relatively short timescales we are consuming a whole galaxy’s worth of energy. (At that point, we have to stop growing unless you think we can somehow harness ~3% of another galaxy within the next year after capping out our own, or for that matter spread across the entire Milky Way in 2500 years -- this is trivially, obviously absurd unless you bring FTL into the equation, and even attaining a few percent of c is currently unthinkable in practical terms).
Also, you’re missing the point of the essay—that this picture emerges from the most ludicrously favorable assumptions in favor of continued growth: that we can only focus on growing the energy sector to the exclusion of worrying about anything else, and that we don’t need to worry about thermodynamic limits to efficiency, and that we don’t need to worry about a piddly little thing like the speed of light once we’ve enclosed the sun in a Dyson sphere and need to keep up the growth rate by expanding into the galaxy at large. Even with that working in favor, we eventually run out of galaxy and have to stop growing. Once you understand that, the only thing left to be argued is where the inflection point lies.
Saying that limits to growth is an argument in favor of civilizations being more likely to spread out, is like saying that the possibility of extinction is an argument in favor of some arbitrary evolutionary adaptation in a population of organisms. It’s getting the important causal bits backwards.
we should be able to notice this for galaxies orders of magnitude farther away than Andromeda.
If it happened long enough ago for the signal to reach us. Andromeda is close (2.5 millions light years), but for a galaxy two orders of magnitude farther away (250 millions light years away), this starts being significant : maybe there is a galaxy whose Dysonification started 250 millions of years ago, and was completed 200 millions of years ago, but we don’t see it because the signal didn’t reach us yet.
What would we expect to see in terms of signals from eg, Andromeda if alien life arose there 100 million years ago and is currently inhabiting almost all of it, assuming they weren’t deliberately sending signals to us?
Well, the most obvious thing is we’d probably see signs that stars are being used. For example if a sizeable fraction of the stars in Andromeda had Dyson spheres, or had stellar lifting, we’d be able to see that from here because the star’s profiles would look different. For example, in the case of a Dyson sphere we’d expect to see much more of the radiation in the infrared range . In fact, if one has Dysoned a large fraction of the stars of a galaxy, we should be able to notice this for galaxies orders of magnitude farther away than Andromeda.
Why?
I mean, I get the assumption here—that we’ve experienced a geometric surge in energy use, economic growth and several other things as a result of the Industrial Revolution, and it hasn’t disappeared yet—but it seems like a potentially important one to question. What would you expect to see if you’re wrong, if the Cold War-era visions of high-energy, superadvanced civilizations or their Singularitarian cousins, the visions of superpowerful AGI and/or uploaded humans are based on the assumption things won’t regress to the mean?
What would you ever see from Andromeda, in that case? Hell, what would you even see from Alpha Centauri if that were the case?
That’s a good point. It is possible that the problem is that large scale engineering projects and the like simply don’t happen. And if that’s the case then it may be that things would look very similar to what we see. In a similar vein, there may be some as yet undiscovered loophole or exception to the laws of thermodynamics that makes harvesting stars unnecessary (this seems unlikely). But not all of these things are purely about energy consumption. While a Dyson sphere or ringworld is nice from an energy standpoint, they also provide living space for growing populations. Yes, it could be that populations simply level off (and Japan and Western Europe do show that that can happen). But at this point we need to now have a lot of assumptions about what every intelligence species does. If only a small fraction try to harvest a lot of energy and only a small fraction don’t control their population growth, then one would expect to probably see something. The idea that not a single species out there tries these sorts of things seems about as surprising as there simply not being anyone out there to do it.
Not so—you only need to posit that sustained growth spurts like the one we’re living through are anomalies, and subject to some rather significant limits.
The essay you linked to is essentially focused on what happens if you stay at a single star. If anything, it should be an argument as to why to expect things to spread out: having a lot more planets and stars means one has a lot more energy at one’s disposal.
Nnnooooo, read it again.
In other words, keep up the paltry growth rate listed at the start of the essay, and take the fantastically-favorable assumptions that go with it (like 100% efficiency) and you find that even if we’re surrounding every star in Dyson spheres we can’t keep up with growth, because within relatively short timescales we are consuming a whole galaxy’s worth of energy. (At that point, we have to stop growing unless you think we can somehow harness ~3% of another galaxy within the next year after capping out our own, or for that matter spread across the entire Milky Way in 2500 years -- this is trivially, obviously absurd unless you bring FTL into the equation, and even attaining a few percent of c is currently unthinkable in practical terms).
Also, you’re missing the point of the essay—that this picture emerges from the most ludicrously favorable assumptions in favor of continued growth: that we can only focus on growing the energy sector to the exclusion of worrying about anything else, and that we don’t need to worry about thermodynamic limits to efficiency, and that we don’t need to worry about a piddly little thing like the speed of light once we’ve enclosed the sun in a Dyson sphere and need to keep up the growth rate by expanding into the galaxy at large. Even with that working in favor, we eventually run out of galaxy and have to stop growing. Once you understand that, the only thing left to be argued is where the inflection point lies.
Saying that limits to growth is an argument in favor of civilizations being more likely to spread out, is like saying that the possibility of extinction is an argument in favor of some arbitrary evolutionary adaptation in a population of organisms. It’s getting the important causal bits backwards.
If it happened long enough ago for the signal to reach us. Andromeda is close (2.5 millions light years), but for a galaxy two orders of magnitude farther away (250 millions light years away), this starts being significant : maybe there is a galaxy whose Dysonification started 250 millions of years ago, and was completed 200 millions of years ago, but we don’t see it because the signal didn’t reach us yet.