1. The speed of light is a hard speed limit. This means there's also no cheating with warp drives, other forms of FTL, crossing dimensions, parallel universes or time travel; and
2. The laws of thermodynamics as we understand them hold true.
then the outcome of spacefaring civilization I believe is generally inevitable. That is, the ultimately limiting factor is energy and mass.
The easiest way to get both is with Dyson Swarms. This requires no new physics and no exotic materials.
If so, then a galaxy-spanning civilization is going to be completely obvious from a million light years away from the spectrum. Why? Because a full Dyson Swarm would have a very unique spectrum, specifically very little visible light and a lot of IR. That's just basic physics. The only realistic way to get rid of heat in space is to radiate it away and the wavelength of that is a function of temperature.
This is discussed in the context of the Fermi Paradox, which has the advantage that you don't need to determine what every alien civilization does, you just need to know if there are any exceptions.
Example: if there were 1000 spacefaring civilizations in the Milky Way, what are the odds that all 1000 of them (assuming they were within out light cone) would remain quiet or hidden? Couple that with mass and energy ultimately being limited then there is a strong incentive and advantage in becoming as large as possible. So even if 99% of civilizations remain quiet, the 1% will still make themselves visible.
Additionally, on the notion of hidden civilizations in particular, it's essentially impossible to remain hidden to a K2 or K3 civilization so there's really no point.
This is what gives me confidence that the Milky Way isn't teeming with spacefaring life. In fact I consider it much more likely we're the only such civilization in the Milky Way (within our light cone).
Seems like a good theory, but when I read something like this it always makes me think about any of the sci-fi I've read that was written 50-75 years ago.
They're also full of what were at the time good theories, but that are now so wrong it often makes reading the story difficult, even with my fairly rudimentary modern astrophysics knowledge.
In all honesty I think it's more likely any sufficiently advanced civilization capable of interstellar travel has probably descended entirely into virtual reality or a singularity.
I mean, what would you prefer? Being the star of your own personal VR space, the next Malcolm Reynolds, space cowboying around where you are the entire focus of that reality. Or schlepping it over to another star in a generation ship or whatever where even if you were somehow still alive when it arrived, you'd be landing on a planet that will probably instantly kill you.
There are several differences between these old predictions and now:
1. We're now assuming based on the limits of known physics rather than the expected limits of technology. My father told me he once read a book that said it was impossible to go to the Moon because it would take 750 years to get there. The speed of light was known at that time but assumptions were made about the limits of acceleration and velocity that weren't grounded in science;
2. Things like the rocket equation are important. Specifically, the reaction mass problem. Even more specifically, the only way for an independent body to accelerate in space that we know of is by expelling mass (or energy). You need to carry that mass and this quickly becomes inefficient.
A good example of this is how people have recently started to say "if we just accelerate at 1G we can get to Alpha Centauri in a few years". 1G acceleration sounds easy but it's not.
So how would you travel between stars? I think it most likely that you'd use a ton of energy to accelerate (or decelerate) a vessel with lasers on a solar sail. Why? Because energy from a star is abundant and cheap and it doesn't require carrying reaction mass.
If you accept that, then the need for Dyson Swarms becomes more obvious.
3. Breaking the 2 assumptions I listed makes spacefaring life more common not less. By this I mean we only really need to consider a million light years (of light cone) because of the speed of light. If FTL or even time travel were possible, then you need to consider a volume of spacetime orders of magnitude larger.
The thing about the "they'd just descend into VR" is that you must explain why one hundred percent of all entities capable of doing that decide to do that.
Moreover, even if you do descend into VR, if you have a civilization capable of safely doing that, you need to explain why 100.0000...% of them never say "hey, I sure could have a lot more VR resources all to myself if I just sent this probe over to that star system over there and converted it into computronium".
By the time you get to this level, you don't need to worry about "planets that will instantly kill you".
Some sort of "singularity" where they escape our universe would explain the emptiness of the sky. However, every year the places where such a thing could hide in our physics gets a bit narrower, and we have literally zero reason right now to believe that such a thing is possible. I have no problem speculating, but I prefer to keep the grounded and ungrounded speculation clearly delimited, and right now this is definitely on the ungrounded side.
(Side not, not targeted at you mattmanser but just to prevent me posting another message, it's really tedious to attack someone engaging in grounded speculation by pointing out that ungrounded speculation exists. Yes, it's possible that humans are just uniquely stupid and there's some easy mechanism to create and escape into infinite energy subuniverses and half the planets in the universe have had dozens of alien civilizations already do so, it's possible that aliens are using energies we've never even heard of to communicate, and it's possible that psychic waves are radiating right through us this very second telling us how to do it, but that's ungrounded speculation. It doesn't mean that we must therefore give up all grounded speculation because "what if, like, the aliens are all psychics that escaped into the ninth dimension? you can't prove they aren't, man.")
I would not choose to be the star. Observing substance (ab)use and suicide among celebrities and the affluent, it seems clear that a “starring role” in life is not an automatic ticket to happiness or fulfillment.
For me at least, a lot of the meaning in life comes from dealing with cold hard reality. Updating my strengths and my belief systems to be more aligned with a disinterested external world. Connecting with, learning from, and sharing with other humans what it all means and what it’s like to be part of this whole thing, to get a more complete understanding of the human experience.
Consider—if we were one unified consciousness with total understanding existing in absolute bliss, what would there be to do, to discuss? We might produce a limited world like our own to make existence more meaningful.
> In all honesty I think it's more likely any sufficiently advanced civilization capable of interstellar travel has probably descended entirely into virtual reality or a singularity.
Or instead of growing larger, growing smaller and becoming more efficient. Microscopic organisms with free will wouldn't be needing Dyson sphere to power their civilization.
Or realization that existence is a pain and that there's no point in pursuing it after the civilization reaches certain level. This is a conversation-ender, So wouldn't even make a good Sci-Fi unless say that civilization decides to put every other civilization out of their misery due their ideology.
> Example: if there were 1000 spacefaring civilizations in the Milky Way, what are the odds that all 1000 of them (assuming they were within out light cone) would remain quiet or hidden? Couple that with mass and energy ultimately being limited then there is a strong incentive and advantage in becoming as large as possible. So even if 99% of civilizations remain quiet, the 1% will still make themselves visible.
I am not sold on this math necessarily. When you ask "what are the odds?" what is that based on? How do we derive these odds at all? We know nothing about how these civilizations would evolve or what their values would be. So how can we assume that out of 1000 that 1% would be visible based on the odds? This sort of assumes that the Drake Equation is accurate, when the last few parts of that equation are complete guesses.
> Additionally, on the notion of hidden civilizations in particular, it's essentially impossible to remain hidden to a K2 or K3 civilization so there's really no point.
And maybe this is the difference. Maybe all 1000 are visible to K2 or K3's because it doesn't matter. But equally all 1000 aren't visible to K1's. We are so far away from K2 that I see no reason to speculate on the likelihood of this since we have literally no basis for this other than some fun thought experiments. And all of this is based on how we view ourselves and apply those same traits to beings we have never met and possibly can't even imagine.
This is simply so far out of our grasp to intelligently speculate on, I tend to just avoid doing it.
So I think where this idea runs into problems is assuming that people actually want or need a Dyson swarm.
The sun puts out 3.846×10^26W. Let's assume a Dyson swarm manages 10% capture efficiency, and a future population of 100 billion. That would result in every person having access to 384TW, or about 25 times Earth's total power consumption.
Clearly, that's far too much power for any reasonable use-case, so at that point you're talking about either a far higher population (quadrillions) or far smaller collection area. Earth's population seems to be destined to cap out at about 9bn, and the trend away from population growth is most pronounced in highly developed energy-hungry countries. So _we're_ probably never going to need a Dyson swarm, anyway...
First, you'd be surprised how many people we can support. Like we could likely support more than a trillion people on Earth. The population of a full Dyson Swarm around our Sun likely caps out in the quadrillions, possibly quintillions.
Second, it's entirely valid to ask the question of whether we'd ever reach such populations. This is of course unknown. As a solution to the Fermi Paradox, the idea of reaching a steady state (or even shrinking to a fragment) seems unsatisfying as a 100% outcome. Once again, it only takes 1 to keep growing and become detectable.
A lot of things are likely to change in the next millenium, for example:
1. I expect we will live much, much longer than we do now;
2. Automation will increase to the point where labour is highly unlikely to be the limiting factor in any kind of industrial output. That leaves resources and energy as the limiting factors. Well, resources are just a proxy for energy. There are several rocky bodies in the Solar System that could, given enough energy, provide unimaginable amounts of raw materials;
3. Despite the wealth of developed nations, we are still living in an era of relative resource scarcity. Individuals in developed nations are certainly generally more prosperous than those in developing nations but it's expensive to raise children in developed nations the way most parents want to raise them: paying for education, housing, etc.
I'm not comfortable making the prediction than the modern trend of having relatively few children per individual in the developed world will continue into an era of longer lives, far more abundance and being freed from the need to work their entire lives to set up those children.
Lastly, there are some very obvious applications for huge amounts of energy, for example:
1. Extracting resources;
2. Vast amounts of computing power. What would you do with this? We haven't been good at predicting this other than to say that more bandwidth and more computing power has thus far always found applications that people want. One obvious one is I suspect we'll have VR worlds that people will basically live in on a scale we can't possibly yet imagine;
How can we be sure that something we have classified as a Red Dwarf star isn't a Dyson Sphere? All of the energy of the star has to be vented eventually, so a Dyson Sphere should glow like an end of life star that has expanded to the diameter of the Sphere.
Also, how do you tell the difference between a solar system full of orbitals vs. a young solar system that has not had the orbital lanes cleared by planets?
I don't believe that any Red Dwarf could be mistaken for a full Dyson Swarm. Some people more knowledgeable than me have put a lot of thought into the science of this. You can probably find a more satisfying answer.
As for the second part, that's easy. There are two key differences:
1. Young solar systems are around young stars and young stars are... young. We can typically age stars, particularly those close by; and
2. A protoplanetary disk is, well, a disk. A full Dyson Swarm is a sphere. To be clear, it's not a rigid sphere, it's just a collection of orbitals that end up occluding the star they orbit in the same way as small water droplets form a cloud or fog.
Alsos I suspect that a protoplanetary disk, even if we're directly on its plane, won't be as dense as a Dyson Swarm.
I don't know if we can tell it for any particular star, but we can reason about large numbers of stars. We have a decent model of how stars must age, given their mass and composition; we have a decent model of how that composition must have evolved as the universe ages, so if there were many Dyson spheres around then I think that should be observable as there being "far too much" red dwarfs compared to how many we should observe.
Are we sure we aren't seeing signs of alien life? I mean so much of astronomy is based on just observation, is it possible some phenomenon we observe is actually the result of an alien civilization and not natural?
Sure, we haven't seen a Dyson swarm, but it's not like we've been looking super hard, and we're assuming that a Dyson swarm/sphere is practical to make and build. If a civilization were to develop a way to, say, directly convert matter to energy, the Dyson sphere/swarm is actually the less efficient option.
It's possible of course, and every so often some new weird anomaly is detected, and aliens are suggested. But mostly a natural explanation is found. The WOW signal and Oumuamua are one of the few exceptions, but natural explanations have been suggested for both.
The thing is we know about natural phenomenon. We don't know whether aliens exist and are detectable. Occam's razor would favor existing natural explanations. Stars, planets, comets and what not are common throughout the universe.
> Couple that with mass and energy ultimately being limited then there is a strong incentive and advantage in becoming as large as possible.
Unless you can transmit power over infinite disctance without loss, you get diminishing returns as you expand. Eventually the amount of energy you can beam back from a new dyson swarm does not justify the cost of building a new dyson swarm. There is no incentive to expand beyond that point. For reasonable engineering estimates, such a range is still very small on galactic scales.
>This is what gives me confidence that the Milky Way isn't teeming with spacefaring life.
Bear in mind that we humans are a spacefaring species. It seems entirely feasible to me that there could be a multitude of intelligent but "quiet" species limited as we are to probes and at best inter-system rockets, even that 100% of spacefaring civilizations thus far remain so, simply because getting to the "Let's Dyson swarm our sun and become Vorlons" stage is far, far more difficult than it appears on paper.
> This requires no new physics and no exotic materials.
It could be that Dyson Swarms are possible, but we have 0 examples of space industries so far.
It could be an economical impossibility, it could be that the means to easily convert matter into energy is discoverable before the means to economically produce a Dyson Swarm, thus a Dyson Swarm is not necessary to orbit that close to a Star.
It could be that the means to capture dark matter is right around the corner, so there's no need to estinguish stars to preserve them.
It could be that the means to capture dark energy is also around the corner and there's no need to bother with altering the universe in any way, in fact, it would be a shame to do so.
It could be that once a species is advanced enough to transcend its own biology and once it becomes kind of immortal, it no longer reproduces.
I'm just pointing out counter arguments, I'm on the opinion that we are completely alone in our Milky Way and most likely the entire Universe. As in there is no bacteria outside our Solar System, anywhere, but there is no way to know yet.
Or every species consumes its planets resources on phones and cars, imploding the environment before the necessary engineering feats to get them to the stars come along.
My money is on it being too infeasible engineering wise due to resource exhaustion just building the infrastructure to get there. The carbon feedback loop creating disposable junk is destabilizing stable human climate.
I lean towards the idea we’ll have to move away from industrialism at the scale we apply it today.
Perhaps synthetic drugs can grow neuron structure that mimics the experience. Or helps acquire muscle memory from skills based work.
Trip balls on the couch for 20 minutes and live life believing I just got from Mars Base 1 and have Zappa opening for me wouldn’t be so bad.
> The only realistic way to get rid of heat in space is to radiate it away and the wavelength of that is a function of temperature.
Then why would it definitely be IR? Couldn't a different form of intelligence thrive at a completely different temperature, and rely on elements that have phases that are useful to them at different temperatures?
So the wavelength of black body radiation is called Wien's Law [1]. If you look at the electromagnetic spectrum [2], the IR spectrum is 25 μm to 2.5 μm.
Compare those two and you'll see pretty much any reasonable range of temperatures has a heavy IR element.
Some things to consider:
1. Tungsten has probably the highest melting point at ~3700K. It seems unlikely that complex matter of any kind can realistically survive at such extreme temperatures;
2. Heat above a certain level can itself be used to generate energy in a straightforward fashion. This itself will generate waste heat, most likely at a much lower temperature.
As an aside, recycling heat is often raised as an objection to the IR signature issue with Dyson Swarms but that ignores thermodynamics. Let's say heat recycling for a star like the Sun is 90% effective then that's still 10% energy lost and 10% of the Sun's output is still massively significant.
If there's perfect recycling, well that ignores entropy.
It's not impossible that something like solving the cosmological constant problem could lead the way for harvesting zero point energy. If supersymmetry exists, which is a big if, physics would become a whole lot more exciting.
This would make Dyson Spheres unnecessary for advancement on the Kardashev scale.
Even if that were possible, it's only 6e-10 J/m^3 [1].
Want to keep a 10W LED light on? That's 10 J/s, so you need to extract all dark energy from 17e9 m^3 of space (roughly a cube with a side of 2.5 km) every second.
TLDR: a bright infrared source is differentiable from a dim infrared source.
If (big if) you can be confident about the distance of the object, that'll help tell you the total power output. If you have total power output and the black body spectrum, you can gauge it's size. A brown dwarf is, notably, small. If you took Sol and put a dyson swarm around it, the eventual power output would stay the same, just shifted colder as the light is now the waste product of all the industrial activity we did with it (minus any anti matter or magic matter fabrication we did) as opposed hot plasma collisions.
I think it sounds daft to think speed of light is a hard speed limit, and there is absolutely a way to "cheat".
Because aliens are here, and they certainly didn't travel at the speed of light to get here. That doesnt work at all. It's way too slow.
My bet is they are extracting energy from space itself, what we call vacuum and we think there is nothing there. And I also think the speed of light only applies to things in our physical universe. Frequently these alien ships blink in and out of our reality. There is much we don't understand as humans.
"If we assume that our knowledge is the pinnacle of knowledge, we are the first to reach it" is a bit tautological, no?
You can apply a very similar reasoning to an isolated tribe stuck at, say, stone-age level on a remote island. With barely seaworthy canoes. They very likely have no idea we exist, and their assumption will be that if there were better canoes, and people had them, they would've made contact. So clearly, they must be among the first.
I am continually amused by the gyrations we go through to avoid saying "we don't know".
I mean, last I checked we couldn't even account for 85% of the matter in the universe that should exist according to the laws of physics as we know them. If we can't even find the vast majority of matter, why do we think we'd do better with civilizations?
I think (1) is probably the main questionable assumption, to be honest. Let's take as given that travel faster than light via some form of cheating isn't possible. Under that assumption, for mass interstellar travel in reasonable time, you would require the ability to produce vast amounts of cheap energy (either via fusion on the starship, or antimatter produced with cheap energy at home and used on the starship, or by some other means).
And at that point, where is the incentive to colonize other star systems? You're still probably not going to be able to move a meaningful part of your population, and if you can produce energy that cheaply you can sustain a large population in comfort at home.
It's not inconceivable that there are advanced aliens all over the place, but that interstellar travel is basically limited to probes for pragmatic reasons.
I think when the Fermi Paradox was brought in, there was still some lingering Malthusian idea that geometric population expansion was inevitable. We now know it very much isn't, at least for us. That changes things.
We always assume that civilizations expand into space without consideration for benefit, but I don't think that will be the case, honestly.
Should we want a colony on another planet? In another star system? Absolutely. It doesn't take much expansion for us to achieve the goal of having a 'redundant backup' for humanity.
Beyond that, there has to be some sort of economic incentive to drive it. Given there is little chance we can economically trade between planets, much less between star systems, I don't think that incentive is there.
The big issue here is different understanding of "reasonable time". The galaxy is very large, and the time spans involved are very large, but they are not in the same ballpark of "large", the time gaps involved are so much larger. If one civilization gets their evolution of intelligent life just 1% quicker than us, that's a head start of 50 million years. On that scale, "reasonable speed" required to fill the galaxy (to use round numbers, 10000 "hops" of 10 ly each for 100000ly distance across the whole galaxy) means something like a planet launching a single colony ship to a nearby star once in 5000 years (and the new colony populating the planet and launching another ship in 5000 years, which seems quite reasonable). You don't need FTL, you don't need fast ships, you don't need many ships, just one generation ship in a few millenia moving at 0.01c or even less is amply sufficient to colonize all of the galaxy many times over in that time range. And if someone was 2% or 3% faster than us, then they'd have even more excessive time to swarm the galaxy even if they're doing it at snail's speed.
So to explain the fact that the aliens aren't swarming everywhere because they can't afford it means accepting that either they launching a single generation-ship every 5000 years is a huge expenditure (which IMHO it wouldn't be even with our current economy size, definitely not an issue with the tech of 2100 or 2200 assuming at least some growth because at that point a Musk-type figure with a wish to "make humanity interstellar" would be able to afford it from private funds) or that we're the first (only?) life in galaxy or that all the aliens before us didn't try to expand, like, at all - because getting just one single rich eccentric every 5000 years (like a bunch of billionaires here are) would be sufficient to make the galaxy swarm with juuust a bit higher tech level than ours now.
We have 1000 stars within the 30 light year radius neighborhood. Traveling at Voyager 1 speed, it takes half a million years to do a 30 light year trip. [1]
Given another half a million years for bootstrapping at the destination for ten more probes, we can send ten more probes, 1 million years from the launch of the first one. At two million years we get 100 probes.
How many probes do we get in a 11 million years? 10^11 probes. We have 10^11 stars in the galaxy.
Dinosaurs roamed the earth aleady 200 million years ago, and died in the mass extinction 65 million years ago. 20 to 5 million years ago was the Miocene, when life was pretty close to modern already. [2]
It's really the nature of exponential growth that makes things seem instantaneous compared to celestial phenomena or evolution. Colonizing the galaxy, even with abysmally slow speeds, is possible, because of the magic of exponentials.
(Certainly this has a lot of assumption, like that you can bootstrap, or that the probe survives the trip. Anyway, optimal probes would be a lot faster and bigger, and there would be more of them. This was just to tie in with something concrete that we know we can do, as Voyager 1 really is out there traveling at 15 km/s, as are Voyager 2, Pioneers and New Horizons probes.)
> And at that point, where is the incentive to colonize other star systems?
Just to put this out there, unless every advanced civilization becomes a hive mind with one unified will, some individual or splinter group or just hodgepodge of determined individuals would probably do it even if there were no incentive, and that's not to point out that incentives are somewhat subjective and differ between individuals and groups. If there are enough individuals on a civilization and the capability exists, some crazy person will do it.
1. No they don't. Spreading at sub-FTL requires redundant self-correcting technology which can run for thousands of years without breaking down. This is about as achievable as FTL. Nothing lasts for thousands of years in deep space without being abraded, fried, nuked, or physically stressed to breaking point.
1b. Assuming you can solve 1. with some kind of magical alchemical spares-generating technology that never fails, the technology also has to be politically and philosophically stable, with reliable and persistent goals. Otherwise you'll get offshoots competing with each other. Which may mean undermining and perhaps even destroying previous settlements. How much independence is enough? How accurate are your initial models going to be?
2. We don't know that for sure. Absence of evidence is not evidence of absence. (We do know weird things happen, but we're not putting any serious effort into researching them, so we don't know what they are.)
3. There's no need to think about this after 1. and 2.
Edit: to put this in context, you don't need to launch a probe. You need to launch a complete perfectly self-reproducing error-free space program. Which can also adapt to local resources.
The turtle would be working with considerably less data, though. Does he know how old his island is? Does he have conclusive evidence of the existence of other islands? Is he aware of the similarity or difference of other islands compared to his own? Would he be able to observe if seafarers were living on a nearby island or does he need to wait for them to actually land on his beach? Does he have a reasonable estimate for the size of the earth? The amount of ocean? For the distribution of islands across the ocean?
Also, since he’s a turtle, he doesn’t, presumably, yet actually know how hard it is to make a boat. The argument for determining whether or not you are the only seafaring species depends, first, on you having attained the ability to travel the seas…
All of that seems necessary before he can conclude whether or not he should consider it ‘surprisingly late’ for his island not to have been reached yet by any seafarers.
But the interesting part of the analogy is maybe that the turtle might fool himself into thinking he understands the parameters well enough to estimate this probability - after all, he’s paddled around off the beach and even made it to a nearby rock - so he reckons he’s got a pretty good handle on how hard it must be to travel between islands.
Yeah, but if humans keep existing for millions of years, then the probability for a turtle on the Galápagos Islands to live in the time between when humans started seafaring and when humans visited the islands would be extremely small compared to any other time period.
It's not a matter of limited perspective, it's a matter of the laws of physics. The rocket equation is a harsh mistress. Without FTL or reactionless drives the physics of going to a distant solar system is absurdly unfavorable. It takes many decades/centuries, is a one way trip, and the ability to build a self contained self powered ecosystem that can survive the entire trip without support. Once you have that why bother going to a distant solar system? You have a perfect orbital habitat.
#1 has some huge assumptions built in. A civilization can travel a long distance without visiting every star system between it’s origin and destination.
The limitation could be doubling time not travel time. Sure double every 100,000 years or less and in 4 million years you’ve run out of stars in the Milky Way which is an eye blink on cosmic timescales. But, a civilization that’s remote terraforming worlds that might greatly slow things down. How long does it take Cyanobacteria to create an oxygen atmosphere for example?
Hanson doesn't think (2) and (3) follow because of the possibility of panspermia. It's possible that our galaxy is the only one in a billion light years that has given rise to life, but there could, because of panspermia, skill be a high probability that a planet in our galaxy outside our solar system has life. See this podcast Hanson did with me: https://soundcloud.com/user-519115521
I felt like I could have used a better articulation of their definition of "loud" and "quiet" aliens, unless these are well known terms in the domain terms and I am just unfamiliar...
The abstracts of papers are intentionally terse, which usually means they are addressed to people already familiar with the field. The paper itself is often more readable (though by no means always!) and it is often worth taking a look at the introduction and conclusion, at least. Here, we have 'To a first approximation, there are two kinds of aliens: quiet and loud. Loud (or “expansive”) aliens expand fast, last long, and make visible changes to their volumes. Quiet
aliens fail to meet at least one of these criteria.'
The incentives and disincentives of exploring other systems is largely unknown. There could be huge risks in visiting other systems in which your own system of origin could be revealed if you happen to find another advanced civilization, I would think if a civilization is even predicted to be in a system, it will likely not be visited.
The Fermi Paradox (where is everyone) has been debated for decades. There are so many possibilities such as great filters (early or late), prime directive, zoo hypothesis, dark forest hypothesis...etc etc. I'm sure you're aware of this, but I included just in case you wanted to explore in more depth. Some really good stuff.
I just heard about the dark forest a couple weeks ago. I believe it to be the model we should proceed with for safety.
Assuming FTL isn't possible, the fact that dark energy makes large sections of the visible universe fundamentally inaccessible is probably a good thing.
Otherwise that is a lot more of the universe that may be ahead of us and would stomp us like ants.
If you look at the realistic reach of the signals of human civilization, it's a few tens of lightyears at best.
And once you factor in how inhumane it'd be to send children out to colonize foreign solar systems ... are we really sure we'll do that? That's 10 generations that live their entire lives in small metal boxes ... without the vast majority of everything we have on earth. Not so much as a single field of grass (or field of anything, building a big room in space will be a great challenge, especially since weightlessness means you don't really need room).
10 generations that will have absolutely zero power to do anything about their situation. It will take 100+ generations before anything remotely resembling earth level comfort will happen (assuming the planets encountered can at any point support human life. If they need to be terraformed, we're easily talking 1000+ generations)
I’m unsure the human rights aspect is going to be the limiting factor. Humans are constantly doing inhuman things. We have a history of forcibly migrating people, it’s not uncommon in our history at all.
I think it’s just as likely that we never spend the engineering effort on a multi-generation colonization ship. Compared to inner-stellar travel inter-stellar travel requires much much more space, robust systems, and reliability. For example, the distance between Earth and the nearest star is over 100,000,000 times the distance between Earth and Jupiter. It’s questionable we’ll ever put the effort into being inner-stellar, but the difference between inner-stellar and inter-stellar is greater than the difference between a paddle board and an aircraft carrier.
Assume we survive climate change as a technologically advanced society & that no other natural disaster or war wipe us out, so you really think you can predict what sort of technology will or will not be available to humans 1,000 years from now? How about 1,000,000?
If in those time spans we figure out a way to sustain 1g acceleration throughout the trip (currently not achievable but less sci-fi than FTL) we can reach nearby stars within the lifetime of the astronauts: https://www.forbes.com/sites/startswithabang/2021/12/30/how-...
But why would a sufficiently advanced civilisation choose to colonise the galaxy with organic human-like beings? Surely it would make far more sense for this hypothetical civilisation to send robots first? A technologically advanced civilisation is also likely to rebuild their organic bodies specifically to overcome these limitations, in which case concerns around terraforming really aren't that big a deal.
The problems you're raising are far more technological in nature than fundamental IMO. I agree that as it stands it wouldn't make much sense to attempt to colonise the galaxy even if we had the rocket technology today, but by the end of the century we'll probably have the kind of technology required to colonise the galaxy (robots, AI, improved battery tech) even if we're still stuck with slow combustion rockets.
> A technologically advanced civilisation is also likely to rebuild their organic bodies specifically to overcome these limitations...
I wouldn't be so sure. It is a question of philosophy really, but there is the argument to be made that a change in form correlates with a change in function, even to the point of changing what a mind is. Suppose humans did that, changed our bodies to survive different environments rather than change environments. At some degree of modification these changed creatures would no longer be human, even in behavior, not just appearance. Where is that degree? And then, what's the point? What is our goal, to spread earth's version of life, it's biosphere? Or to spread minds and create more? Or to spread humanity? If it's the last one, it makes no sense to extensively modify our bodies, because you wouldn't be spreading humanity, just life, or just minds, at which point why not just send tardigrades or awesome computers into space?
This adds a new, unexpected element to the alien visitation theory: the aliens that come here will not be alive at all, they will be robots programmed to extract resources that cannot be reasoned with diplomatically (assuming they are not outfitted with general intelligence). Unless the senders thought ahead and built empathy into the robots, there will be no way to end the invasion other than to kill everything that comes here.
Even our oldest running computers are young by human standards, and downright primitive compared to what we are producing today. Machines are not immortal, at best they are easier to repair than lifeforms but that's not of much use if there's no one to repair them. The voyager probes are in their 40s, and it's not looking like they're going to make it into their 80s. While we can certainly build more robust machines with more redundant components, the fact is without FTL the overwhelming majority of a galaxy is tens of thousands of years away at a minimum[0]. Building things to last over such timeframes in a harsh environment like space may not even be possible, nonetheless practically achievable.
Even if one assumes we can make such long lived machines, the question becomes why? By the time such a craft reaches its destination, every being that worked on its construction, and all of their descendants for many generations, and indeed possibly the civilization itself, will be gone. Even if some institution still remains, it will be too far away to communicate with, nonetheless transfer anything with mass. Whether operated by cloned beings or AI, this new settlement is in no way a part of the originating civilization, at least not any more than some ancient Egyptians shipped off 1000 lightyears away would nowadays be a part of ours. There may be legitimate reasons to set up a few colonies, such as backups in case of solar-system scale catastrophes, but by the time you've expanded out even just 100 lightyears (0.0001% of the galaxy), there are already tens of thousands of systems in your "empire". Of course civilizations don't need to act rationally all the time, even though they might derive no benefit they might do something just because they can. But how many times are they going to do this just because they can? 10 times, 100 times? 10,000 times? Eventually the novelty is going to wear off, and those massive quantities of resources being spent on these extremely expensive spacecraft are going to be repurposed for the betterment of the civilization.
Now let's say that, despite the extreme technical challenge of travelling more than a few tens of lightyears, and despite the complete lack of rational reason to do so, a civilization decides to just keep expanding anyways. Eventually they are going to encounter another civilization. This continuous growth is a threat to any other civilization - even if they agree to leave their neighbors alone, they are still ravenously consuming the resources in the area that such a civilization would want to have access to in the future. It is in their best interests to get the expansionist civilization to stop - possibly by diplomacy, possibly by other means. The expansionist civilization is squandering resources on its expansion, it's likely a young civilization that only recently developed the means to expand, its periphery is thousands of years less advanced than its core region and likely very underdeveloped, it has no means to move its assets to the periphery or concentrate its forces in the short term, and it has extremely long supply chains in the long run. Conversely the neighbors have been using their resources efficiently, they may have been around for a very long time, and they are operating close to their core region. The expansionist civilization will get in a fight eventually, and it will lose. Even if it doesn't get defeated so utterly that it is forced to stop expanding, eventually it will just encounter another civilization that will stop it from expanding.
The only scenario where continuous expansion is possible without FTL travel is if one of the very earliest civilizations in the universe has an inexplicable drive to expand and does so fast enough that no other civilization can arise fast enough to snuff out all possible competing civilizations in their infancy. That we have reached this point in our technological advancement long before a non-FTL civilization could expand throughout the visible universe strongly suggests such a scenario is impossible.
[0] Some people may feel inclined to bring up Von Neumann probes - craft which travel to other star systems, repilicate themselves several times over, and then launch more such probes to more solar systems, thus allowing for exponential growth. This technology doesn't actually make expansion any faster though. Building a probe at A, sending it to B, where it builds a second probe, and then sending that to C will always be slower than building two probes at A and sending one each to B and C directly. There is also no benefit to longevity - building a new probe is equivalent to replacing every component of the original.
That’s an accurate statement the reality is that any civilization that develops sufficient level of technology to allow it to spread across a single galaxy or even to adjacent star systems would be able to use that technology to find better alternatives in their own star system.
That’s if civilizations even live that long in the first place.
Minimal fraction of suns energy output would allow insane number of humans to survive. And it will be around a while so there is really no hurry to move out.
Kinda comes to calculation that when earliest potentially space faring civilisation runs out of their sun? And can't adapt to live in system. For us that would still be at least few billions of years if not more with proper preparation.
> If you look at the realistic reach of the signals of human civilization, it's a few tens of lightyears at best.
And probably getting smaller every year. We don't have as many giant multi-megawatt radio transmitters as we used to. Quite conceivably it could be ~zero in a few decades, as everything goes fibre and cellular.
Even our multi-megawatt transmitters being detectable for tens of light years is largely a myth. Omnidirectional broadcasts need to be powerful just to be detected several miles away thanks to the inverse square law. Most powerful TV and radio transmitters won't be detectable too far outside the solar system.
It takes a lot of power (or a highly directional antenna) to send a detectable signal detectable light years away. The only unintentional signals we generate are high power weather and military radar. Those are very tight beams that sweep the sky. Any interstellar eavesdropper would need to have the beam sweep over them to detect it. Even then it would be a transient signal with no guarantee of repetition since everything is it motion.
It would be like us being a mile apart in the blackest of night and you swinging a laser pointer around. Even if I'm looking specifically for you and have a general idea where you are the odds are vanishingly small your laser pointer will happen to be visible to me. You'd have to be specifically pointing it at me to even have a hope of me seeing it.
I never understood these kind of analyses that talk about aliens reaching "humanity’s level" like it's inevitable or somehow special.
We could blast radio waves with ABBA songs into space to find whether there are other Swedish-speaking civilizations, or whether we are alone in the Universe. We don't because it's silly to think of the Swedish language as a necessary step for "advanced life".
Why do we think that human-like intelligence is special?
It's only futile to blast ABBA songs (or other human-like signals) into space if we think human-like intelligence is special.
It's precisely because we believe human-like intelligence is _not_ special that blasting (or listening for) space signals makes any sense. The assumption is that other civilizations will converge on some of the same technology that we've developed and recognize a patterned signal when they see one.
> The assumption is that other civilizations will converge on some of the same technology that we've developed and recognize a patterned signal when they see one.
Why would anyone think that?
No other species in the history of the Earth has the ability to create human languages. Nobody outside the tiny group of 0.1% of humanity can speak Swedish. No single rock we've observed outside our planet can even understand the concept of a word like "Läderlappen" or "Knullruffs".
Those 10 million people are alone in the Universe as developers and speakers of Swedish just like these 7.9 billion people are alone in the Universe as developers and users of human-like intelligence.
Blasting signals into space is the same as singing ABBA songs really loud: maybe a sci-fi civilization of Klingons who speak a Swedish-like language could understand it, but in our Universe there's no chance that some extraterrestrial thing will converge on the same languages or technologies as we did.
I think what he means by "special" is that "every civilization will go through the same phases we go through" and not "we are the only ones that have it." This disagreement really hinges on that very disparate use of the term "special."
One issue here is that there’s no economic reason for the home planet to mount the sort of resources it would take to fund an interstellar trip. Stars are farther away than you think. The only way I can see that it would happen is for religious reasons, if the belief system of the religion required them to do it. Because there’s no economic reason.
The other issue is that it’s not clear how long technological civilizations last. We might be close to exhausting our own planet just 150 years after the invention of radio. Maybe technological civilizations bloom in the dark like beautiful flowers, then burn out quickly before they can spread to other systems.
I find these kinds of analyses to be hopelessly oversimplified.
First of all, we are talking about predicting the actions of superintelligent aliens. We aren't talking about slime molds or a bacterial infection, but beings with more intelligence than us, like orders of magnitude more complicated reasoning processes. They are effectively unpredictable, because if they weren't, wouldn't we be just as smart as they are? That level of intelligence comes with new levels of reflectiveness that are frankly not accessible to our weak brains. Like, maybe after reaching the next level of enlightenment, they decide that expansion throughout the universe like a worm is not actually what they want or that is what is good for the universe? Maybe they decide to rather study the universe and not interfere, the way biologists study, say, apes, without wanting to disrupt their natural behavior with their presence? Or maybe superintelligent beings find a way out of our universe, and pass into another dimension (cyberspace? black holes? disappearing through quantum foam? heaven?). Or maybe something else insane happens, like being superintelligent inevitably makes you completely terrified of everything, because you realize how powerful other aliens are and your calculations unequivocally show it's safer to stay at home and fart around doing the super-intelligent analog of baking chocolate-chip cookies? Not being superintelligent, we are like ants trying to contemplate human civilization. We have no context or experience, and we simply don't have the mental capacity to even imagine what we don't know.
Second, these probabilistic models are so fundamentally stupid. It's impossible for us to reliably estimate the probability of any event that's happened only once (without reasoning about the process that gave rise to that event), as we cannot estimate posterior probabilities without lots of samples. And humans on Earth have a massive chain of single-occurrence events that all seem to be absurdly improbable. Besides that, and perhaps even because of that, it's not even a foregone conclusion that our universe even selects from the middle of the distribution (i.e. is not biased). We could perfectly estimate the shape of a probability curve and yet live in a universe that stubbornly selects from the end of the distribution, all the time. All of our math could be totally right, but crazy shit just keeps happening.
Third, the anthropic principle is a total bitch. It means that we will never be able to estimate probabilities of events that were required to create us, because no matter how improbable they were, if they didn't happen, we're not even here to argue about it. If there are infinite universes (a multiverse, see Tegmark), then forget this whole mathematical sophistry, because then there is no need to live in some "average" universe; we can easily live in some stupidly improbably snowflake universe that has the 90 trillion improbable things that make apes possible; infinity doesn't care.
Your comment deserves a much longer response than I can give it, but you seem to be saying that it's impossible to know anything with any certainty, and that is absolutely true. I'm sure all the authors of this work would agree with you.
Coming to conclusions/guesses requires starting with some assumptions about about how the universe works. It's important not to lose sight of those assumptions and very important to have a discussion about how likely each assumption is to be true. So to the extent that anyone is saying "this is definitely how the universe is", I wholeheartedly agree with you.
However, it feels like you're being a little too epistemically nihilistic here. This kind of speculative work always starts without confirmation or any particular reason to believe it beyond how well it matches the curve it was fit to.
To quibble with a particular, this work doesn't attempt to predict the actions of super-intelligences, it's not making the claim that most civilizations will be "grabby", it's making predictions about what will happen under the assumption that some subpopulation of them decides to become grabby.
I am not being nihilistic, I am being realistic. We really can't predict the actions of superintelligence, full stop.
Here's what I mean. What makes the lights on your router blink? Usually, it's packets going in and out. At a coarse level, if your computer is doing something on the internet, the lights are gonna be blinking. But now increase the resolution, from seconds, to milliseconds, to microseconds, to nanoseconds. At a nanosecond level, whether the LED is on or off depends on whether a packet is going over the wire right this nanosecond. Whether a packet is earlier or later by a nanosecond is influenced by a bazillion variables: the router's internal state, its own operating system's scheduling, whether the devices connected to it are sending packets at it, dragging in their state, their scheduling, their programs, packet queues, etc. Gigabytes of state, changing nano-second to nano-second. Oh, and it's connected to the internet. When does the internet decide to send a packet to this router? If those are faster or slower by a nanosecond, it could be due the state along the entire path, all of which are servicing packets from all over the place, decided upon by super-complex distributed systems--datacenters full of them. So even the blinking of a router LED is connected to a supremely complex causality tangle. To understand the blinking nano-second to nano-second, you basically have to replicate the details of the entire internet. So, if I were to ask you instead to predict what will happen tomorrow at 3:33am--will your router be blinking, let's say, fast or slow? Who knows. A DDoS might crop up because someone was mad at Amazon, or maybe your OS downloads a software update, or maybe you are up watching Netflix, or maybe the whole thing is down because nuclear war. It's progressed so far from a simple bell curve that probabilistic reasoning, I would argue, is useless. And that's just without the internet being "intelligent"! Now assume the internet knows this prediction game is afoot, and it gets to bet too. The whole thing goes off the rails.
No, we can't predict what aliens will do. This paper is a mathematical exercise that might apply to bacteria or video game characters, not interstellar civilizations.
The paper addresses your first point in section 7 'Model Rationale'. Essentially, anything that is subject to self-propagation is going to tend to expansionism at a large enough scale, superintelligence or not. The only thing that would prevent this is wide-scale coordination (e.g. a universal autocratic government). And if any species did accomplish this, they would just be one of the 'quiet' ones.
That's my take, they wrote it better though. That section is short, straightforward, and worth reading.
Readit News
1. The speed of light is a hard speed limit. This means there's also no cheating with warp drives, other forms of FTL, crossing dimensions, parallel universes or time travel; and
2. The laws of thermodynamics as we understand them hold true.
then the outcome of spacefaring civilization I believe is generally inevitable. That is, the ultimately limiting factor is energy and mass.
The easiest way to get both is with Dyson Swarms. This requires no new physics and no exotic materials.
If so, then a galaxy-spanning civilization is going to be completely obvious from a million light years away from the spectrum. Why? Because a full Dyson Swarm would have a very unique spectrum, specifically very little visible light and a lot of IR. That's just basic physics. The only realistic way to get rid of heat in space is to radiate it away and the wavelength of that is a function of temperature.
This is discussed in the context of the Fermi Paradox, which has the advantage that you don't need to determine what every alien civilization does, you just need to know if there are any exceptions.
Example: if there were 1000 spacefaring civilizations in the Milky Way, what are the odds that all 1000 of them (assuming they were within out light cone) would remain quiet or hidden? Couple that with mass and energy ultimately being limited then there is a strong incentive and advantage in becoming as large as possible. So even if 99% of civilizations remain quiet, the 1% will still make themselves visible.
Additionally, on the notion of hidden civilizations in particular, it's essentially impossible to remain hidden to a K2 or K3 civilization so there's really no point.
This is what gives me confidence that the Milky Way isn't teeming with spacefaring life. In fact I consider it much more likely we're the only such civilization in the Milky Way (within our light cone).
They're also full of what were at the time good theories, but that are now so wrong it often makes reading the story difficult, even with my fairly rudimentary modern astrophysics knowledge.
In all honesty I think it's more likely any sufficiently advanced civilization capable of interstellar travel has probably descended entirely into virtual reality or a singularity.
I mean, what would you prefer? Being the star of your own personal VR space, the next Malcolm Reynolds, space cowboying around where you are the entire focus of that reality. Or schlepping it over to another star in a generation ship or whatever where even if you were somehow still alive when it arrived, you'd be landing on a planet that will probably instantly kill you.
1. We're now assuming based on the limits of known physics rather than the expected limits of technology. My father told me he once read a book that said it was impossible to go to the Moon because it would take 750 years to get there. The speed of light was known at that time but assumptions were made about the limits of acceleration and velocity that weren't grounded in science;
2. Things like the rocket equation are important. Specifically, the reaction mass problem. Even more specifically, the only way for an independent body to accelerate in space that we know of is by expelling mass (or energy). You need to carry that mass and this quickly becomes inefficient.
A good example of this is how people have recently started to say "if we just accelerate at 1G we can get to Alpha Centauri in a few years". 1G acceleration sounds easy but it's not.
So how would you travel between stars? I think it most likely that you'd use a ton of energy to accelerate (or decelerate) a vessel with lasers on a solar sail. Why? Because energy from a star is abundant and cheap and it doesn't require carrying reaction mass.
If you accept that, then the need for Dyson Swarms becomes more obvious.
3. Breaking the 2 assumptions I listed makes spacefaring life more common not less. By this I mean we only really need to consider a million light years (of light cone) because of the speed of light. If FTL or even time travel were possible, then you need to consider a volume of spacetime orders of magnitude larger.
Moreover, even if you do descend into VR, if you have a civilization capable of safely doing that, you need to explain why 100.0000...% of them never say "hey, I sure could have a lot more VR resources all to myself if I just sent this probe over to that star system over there and converted it into computronium".
By the time you get to this level, you don't need to worry about "planets that will instantly kill you".
Some sort of "singularity" where they escape our universe would explain the emptiness of the sky. However, every year the places where such a thing could hide in our physics gets a bit narrower, and we have literally zero reason right now to believe that such a thing is possible. I have no problem speculating, but I prefer to keep the grounded and ungrounded speculation clearly delimited, and right now this is definitely on the ungrounded side.
(Side not, not targeted at you mattmanser but just to prevent me posting another message, it's really tedious to attack someone engaging in grounded speculation by pointing out that ungrounded speculation exists. Yes, it's possible that humans are just uniquely stupid and there's some easy mechanism to create and escape into infinite energy subuniverses and half the planets in the universe have had dozens of alien civilizations already do so, it's possible that aliens are using energies we've never even heard of to communicate, and it's possible that psychic waves are radiating right through us this very second telling us how to do it, but that's ungrounded speculation. It doesn't mean that we must therefore give up all grounded speculation because "what if, like, the aliens are all psychics that escaped into the ninth dimension? you can't prove they aren't, man.")
I would not choose to be the star. Observing substance (ab)use and suicide among celebrities and the affluent, it seems clear that a “starring role” in life is not an automatic ticket to happiness or fulfillment.
For me at least, a lot of the meaning in life comes from dealing with cold hard reality. Updating my strengths and my belief systems to be more aligned with a disinterested external world. Connecting with, learning from, and sharing with other humans what it all means and what it’s like to be part of this whole thing, to get a more complete understanding of the human experience.
Consider—if we were one unified consciousness with total understanding existing in absolute bliss, what would there be to do, to discuss? We might produce a limited world like our own to make existence more meaningful.
Or instead of growing larger, growing smaller and becoming more efficient. Microscopic organisms with free will wouldn't be needing Dyson sphere to power their civilization.
Or realization that existence is a pain and that there's no point in pursuing it after the civilization reaches certain level. This is a conversation-ender, So wouldn't even make a good Sci-Fi unless say that civilization decides to put every other civilization out of their misery due their ideology.
Even if it was possible, what would "descend" mean -- it would mean that someone could make a perfect virtual clone of me inside a virtual world.
What is the incentive for ME to do that? It's like saying that in a parallel universe a perfect clone of me is a billionaire if I so choose.
> singularity
What does that actually mean?
I am not sold on this math necessarily. When you ask "what are the odds?" what is that based on? How do we derive these odds at all? We know nothing about how these civilizations would evolve or what their values would be. So how can we assume that out of 1000 that 1% would be visible based on the odds? This sort of assumes that the Drake Equation is accurate, when the last few parts of that equation are complete guesses.
> Additionally, on the notion of hidden civilizations in particular, it's essentially impossible to remain hidden to a K2 or K3 civilization so there's really no point.
And maybe this is the difference. Maybe all 1000 are visible to K2 or K3's because it doesn't matter. But equally all 1000 aren't visible to K1's. We are so far away from K2 that I see no reason to speculate on the likelihood of this since we have literally no basis for this other than some fun thought experiments. And all of this is based on how we view ourselves and apply those same traits to beings we have never met and possibly can't even imagine.
This is simply so far out of our grasp to intelligently speculate on, I tend to just avoid doing it.
The sun puts out 3.846×10^26W. Let's assume a Dyson swarm manages 10% capture efficiency, and a future population of 100 billion. That would result in every person having access to 384TW, or about 25 times Earth's total power consumption.
Clearly, that's far too much power for any reasonable use-case, so at that point you're talking about either a far higher population (quadrillions) or far smaller collection area. Earth's population seems to be destined to cap out at about 9bn, and the trend away from population growth is most pronounced in highly developed energy-hungry countries. So _we're_ probably never going to need a Dyson swarm, anyway...
Where have I heard that or something similar before? ;-)
There could be quintilions of amish people farming in a Dyson Swarm :)
Second, it's entirely valid to ask the question of whether we'd ever reach such populations. This is of course unknown. As a solution to the Fermi Paradox, the idea of reaching a steady state (or even shrinking to a fragment) seems unsatisfying as a 100% outcome. Once again, it only takes 1 to keep growing and become detectable.
A lot of things are likely to change in the next millenium, for example:
1. I expect we will live much, much longer than we do now;
2. Automation will increase to the point where labour is highly unlikely to be the limiting factor in any kind of industrial output. That leaves resources and energy as the limiting factors. Well, resources are just a proxy for energy. There are several rocky bodies in the Solar System that could, given enough energy, provide unimaginable amounts of raw materials;
3. Despite the wealth of developed nations, we are still living in an era of relative resource scarcity. Individuals in developed nations are certainly generally more prosperous than those in developing nations but it's expensive to raise children in developed nations the way most parents want to raise them: paying for education, housing, etc.
I'm not comfortable making the prediction than the modern trend of having relatively few children per individual in the developed world will continue into an era of longer lives, far more abundance and being freed from the need to work their entire lives to set up those children.
Lastly, there are some very obvious applications for huge amounts of energy, for example:
1. Extracting resources;
2. Vast amounts of computing power. What would you do with this? We haven't been good at predicting this other than to say that more bandwidth and more computing power has thus far always found applications that people want. One obvious one is I suspect we'll have VR worlds that people will basically live in on a scale we can't possibly yet imagine;
4. Interstellar travel; and, of course
5. Cryptocurrency mining. :)
Also, how do you tell the difference between a solar system full of orbitals vs. a young solar system that has not had the orbital lanes cleared by planets?
As for the second part, that's easy. There are two key differences:
1. Young solar systems are around young stars and young stars are... young. We can typically age stars, particularly those close by; and
2. A protoplanetary disk is, well, a disk. A full Dyson Swarm is a sphere. To be clear, it's not a rigid sphere, it's just a collection of orbitals that end up occluding the star they orbit in the same way as small water droplets form a cloud or fog.
Alsos I suspect that a protoplanetary disk, even if we're directly on its plane, won't be as dense as a Dyson Swarm.
Sure, we haven't seen a Dyson swarm, but it's not like we've been looking super hard, and we're assuming that a Dyson swarm/sphere is practical to make and build. If a civilization were to develop a way to, say, directly convert matter to energy, the Dyson sphere/swarm is actually the less efficient option.
The thing is we know about natural phenomenon. We don't know whether aliens exist and are detectable. Occam's razor would favor existing natural explanations. Stars, planets, comets and what not are common throughout the universe.
Unless you can transmit power over infinite disctance without loss, you get diminishing returns as you expand. Eventually the amount of energy you can beam back from a new dyson swarm does not justify the cost of building a new dyson swarm. There is no incentive to expand beyond that point. For reasonable engineering estimates, such a range is still very small on galactic scales.
Bear in mind that we humans are a spacefaring species. It seems entirely feasible to me that there could be a multitude of intelligent but "quiet" species limited as we are to probes and at best inter-system rockets, even that 100% of spacefaring civilizations thus far remain so, simply because getting to the "Let's Dyson swarm our sun and become Vorlons" stage is far, far more difficult than it appears on paper.
It could be that Dyson Swarms are possible, but we have 0 examples of space industries so far.
It could be an economical impossibility, it could be that the means to easily convert matter into energy is discoverable before the means to economically produce a Dyson Swarm, thus a Dyson Swarm is not necessary to orbit that close to a Star.
It could be that the means to capture dark matter is right around the corner, so there's no need to estinguish stars to preserve them.
It could be that the means to capture dark energy is also around the corner and there's no need to bother with altering the universe in any way, in fact, it would be a shame to do so.
It could be that once a species is advanced enough to transcend its own biology and once it becomes kind of immortal, it no longer reproduces.
I'm just pointing out counter arguments, I'm on the opinion that we are completely alone in our Milky Way and most likely the entire Universe. As in there is no bacteria outside our Solar System, anywhere, but there is no way to know yet.
My money is on it being too infeasible engineering wise due to resource exhaustion just building the infrastructure to get there. The carbon feedback loop creating disposable junk is destabilizing stable human climate.
I lean towards the idea we’ll have to move away from industrialism at the scale we apply it today.
Perhaps synthetic drugs can grow neuron structure that mimics the experience. Or helps acquire muscle memory from skills based work.
Trip balls on the couch for 20 minutes and live life believing I just got from Mars Base 1 and have Zappa opening for me wouldn’t be so bad.
Then why would it definitely be IR? Couldn't a different form of intelligence thrive at a completely different temperature, and rely on elements that have phases that are useful to them at different temperatures?
Compare those two and you'll see pretty much any reasonable range of temperatures has a heavy IR element.
Some things to consider:
1. Tungsten has probably the highest melting point at ~3700K. It seems unlikely that complex matter of any kind can realistically survive at such extreme temperatures;
2. Heat above a certain level can itself be used to generate energy in a straightforward fashion. This itself will generate waste heat, most likely at a much lower temperature.
As an aside, recycling heat is often raised as an objection to the IR signature issue with Dyson Swarms but that ignores thermodynamics. Let's say heat recycling for a star like the Sun is 90% effective then that's still 10% energy lost and 10% of the Sun's output is still massively significant.
If there's perfect recycling, well that ignores entropy.
[1]: https://en.wikipedia.org/wiki/Wien%27s_displacement_law
[2]: http://labman.phys.utk.edu/phys222core/modules/m6/The%20EM%2...
This would make Dyson Spheres unnecessary for advancement on the Kardashev scale.
Even if that were possible, it's only 6e-10 J/m^3 [1].
Want to keep a 10W LED light on? That's 10 J/s, so you need to extract all dark energy from 17e9 m^3 of space (roughly a cube with a side of 2.5 km) every second.
[1] http://www.astronomy.ohio-state.edu/~ryden/ast162_10/notes41...
We can already create W bosons from photon collisions at particle accelerators on earth.
That sounds just like a brown dwarf. How would a Dyson swarm look different?
If (big if) you can be confident about the distance of the object, that'll help tell you the total power output. If you have total power output and the black body spectrum, you can gauge it's size. A brown dwarf is, notably, small. If you took Sol and put a dyson swarm around it, the eventual power output would stay the same, just shifted colder as the light is now the waste product of all the industrial activity we did with it (minus any anti matter or magic matter fabrication we did) as opposed hot plasma collisions.
Because aliens are here, and they certainly didn't travel at the speed of light to get here. That doesnt work at all. It's way too slow.
My bet is they are extracting energy from space itself, what we call vacuum and we think there is nothing there. And I also think the speed of light only applies to things in our physical universe. Frequently these alien ships blink in and out of our reality. There is much we don't understand as humans.
You can apply a very similar reasoning to an isolated tribe stuck at, say, stone-age level on a remote island. With barely seaworthy canoes. They very likely have no idea we exist, and their assumption will be that if there were better canoes, and people had them, they would've made contact. So clearly, they must be among the first.
I am continually amused by the gyrations we go through to avoid saying "we don't know".
I mean, last I checked we couldn't even account for 85% of the matter in the universe that should exist according to the laws of physics as we know them. If we can't even find the vast majority of matter, why do we think we'd do better with civilizations?
And at that point, where is the incentive to colonize other star systems? You're still probably not going to be able to move a meaningful part of your population, and if you can produce energy that cheaply you can sustain a large population in comfort at home.
It's not inconceivable that there are advanced aliens all over the place, but that interstellar travel is basically limited to probes for pragmatic reasons.
I think when the Fermi Paradox was brought in, there was still some lingering Malthusian idea that geometric population expansion was inevitable. We now know it very much isn't, at least for us. That changes things.
Should we want a colony on another planet? In another star system? Absolutely. It doesn't take much expansion for us to achieve the goal of having a 'redundant backup' for humanity.
Beyond that, there has to be some sort of economic incentive to drive it. Given there is little chance we can economically trade between planets, much less between star systems, I don't think that incentive is there.
So to explain the fact that the aliens aren't swarming everywhere because they can't afford it means accepting that either they launching a single generation-ship every 5000 years is a huge expenditure (which IMHO it wouldn't be even with our current economy size, definitely not an issue with the tech of 2100 or 2200 assuming at least some growth because at that point a Musk-type figure with a wish to "make humanity interstellar" would be able to afford it from private funds) or that we're the first (only?) life in galaxy or that all the aliens before us didn't try to expand, like, at all - because getting just one single rich eccentric every 5000 years (like a bunch of billionaires here are) would be sufficient to make the galaxy swarm with juuust a bit higher tech level than ours now.
An example:
We have 1000 stars within the 30 light year radius neighborhood. Traveling at Voyager 1 speed, it takes half a million years to do a 30 light year trip. [1]
Given another half a million years for bootstrapping at the destination for ten more probes, we can send ten more probes, 1 million years from the launch of the first one. At two million years we get 100 probes.
How many probes do we get in a 11 million years? 10^11 probes. We have 10^11 stars in the galaxy.
Dinosaurs roamed the earth aleady 200 million years ago, and died in the mass extinction 65 million years ago. 20 to 5 million years ago was the Miocene, when life was pretty close to modern already. [2]
It's really the nature of exponential growth that makes things seem instantaneous compared to celestial phenomena or evolution. Colonizing the galaxy, even with abysmally slow speeds, is possible, because of the magic of exponentials.
(Certainly this has a lot of assumption, like that you can bootstrap, or that the probe survives the trip. Anyway, optimal probes would be a lot faster and bigger, and there would be more of them. This was just to tie in with something concrete that we know we can do, as Voyager 1 really is out there traveling at 15 km/s, as are Voyager 2, Pioneers and New Horizons probes.)
1: https://www.wolframalpha.com/input/?i=+30+light+years+%2F+vo...
2: https://en.wikipedia.org/wiki/Miocene
Just to put this out there, unless every advanced civilization becomes a hive mind with one unified will, some individual or splinter group or just hodgepodge of determined individuals would probably do it even if there were no incentive, and that's not to point out that incentives are somewhat subjective and differ between individuals and groups. If there are enough individuals on a civilization and the capability exists, some crazy person will do it.
Don't see the reasoning here.
For example, we currently can feed the whole Earth population "cheaply". But the wars didn't end. Same with cheap energy.
E.g. we can try to install vast amounts of mirrors to direct Sun's light towards an accelerating ship. But that won't bring us here more comfort.
1b. Assuming you can solve 1. with some kind of magical alchemical spares-generating technology that never fails, the technology also has to be politically and philosophically stable, with reliable and persistent goals. Otherwise you'll get offshoots competing with each other. Which may mean undermining and perhaps even destroying previous settlements. How much independence is enough? How accurate are your initial models going to be?
2. We don't know that for sure. Absence of evidence is not evidence of absence. (We do know weird things happen, but we're not putting any serious effort into researching them, so we don't know what they are.)
3. There's no need to think about this after 1. and 2.
Edit: to put this in context, you don't need to launch a probe. You need to launch a complete perfectly self-reproducing error-free space program. Which can also adapt to local resources.
This seems... difficult.
Also, since he’s a turtle, he doesn’t, presumably, yet actually know how hard it is to make a boat. The argument for determining whether or not you are the only seafaring species depends, first, on you having attained the ability to travel the seas…
All of that seems necessary before he can conclude whether or not he should consider it ‘surprisingly late’ for his island not to have been reached yet by any seafarers.
But the interesting part of the analogy is maybe that the turtle might fool himself into thinking he understands the parameters well enough to estimate this probability - after all, he’s paddled around off the beach and even made it to a nearby rock - so he reckons he’s got a pretty good handle on how hard it must be to travel between islands.
The limitation could be doubling time not travel time. Sure double every 100,000 years or less and in 4 million years you’ve run out of stars in the Milky Way which is an eye blink on cosmic timescales. But, a civilization that’s remote terraforming worlds that might greatly slow things down. How long does it take Cyanobacteria to create an oxygen atmosphere for example?
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Assuming FTL isn't possible, the fact that dark energy makes large sections of the visible universe fundamentally inaccessible is probably a good thing.
Otherwise that is a lot more of the universe that may be ahead of us and would stomp us like ants.
What is "volume appearance" BTW?
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And once you factor in how inhumane it'd be to send children out to colonize foreign solar systems ... are we really sure we'll do that? That's 10 generations that live their entire lives in small metal boxes ... without the vast majority of everything we have on earth. Not so much as a single field of grass (or field of anything, building a big room in space will be a great challenge, especially since weightlessness means you don't really need room).
10 generations that will have absolutely zero power to do anything about their situation. It will take 100+ generations before anything remotely resembling earth level comfort will happen (assuming the planets encountered can at any point support human life. If they need to be terraformed, we're easily talking 1000+ generations)
I think it’s just as likely that we never spend the engineering effort on a multi-generation colonization ship. Compared to inner-stellar travel inter-stellar travel requires much much more space, robust systems, and reliability. For example, the distance between Earth and the nearest star is over 100,000,000 times the distance between Earth and Jupiter. It’s questionable we’ll ever put the effort into being inner-stellar, but the difference between inner-stellar and inter-stellar is greater than the difference between a paddle board and an aircraft carrier.
If in those time spans we figure out a way to sustain 1g acceleration throughout the trip (currently not achievable but less sci-fi than FTL) we can reach nearby stars within the lifetime of the astronauts: https://www.forbes.com/sites/startswithabang/2021/12/30/how-...
The problems you're raising are far more technological in nature than fundamental IMO. I agree that as it stands it wouldn't make much sense to attempt to colonise the galaxy even if we had the rocket technology today, but by the end of the century we'll probably have the kind of technology required to colonise the galaxy (robots, AI, improved battery tech) even if we're still stuck with slow combustion rockets.
I wouldn't be so sure. It is a question of philosophy really, but there is the argument to be made that a change in form correlates with a change in function, even to the point of changing what a mind is. Suppose humans did that, changed our bodies to survive different environments rather than change environments. At some degree of modification these changed creatures would no longer be human, even in behavior, not just appearance. Where is that degree? And then, what's the point? What is our goal, to spread earth's version of life, it's biosphere? Or to spread minds and create more? Or to spread humanity? If it's the last one, it makes no sense to extensively modify our bodies, because you wouldn't be spreading humanity, just life, or just minds, at which point why not just send tardigrades or awesome computers into space?
Even if one assumes we can make such long lived machines, the question becomes why? By the time such a craft reaches its destination, every being that worked on its construction, and all of their descendants for many generations, and indeed possibly the civilization itself, will be gone. Even if some institution still remains, it will be too far away to communicate with, nonetheless transfer anything with mass. Whether operated by cloned beings or AI, this new settlement is in no way a part of the originating civilization, at least not any more than some ancient Egyptians shipped off 1000 lightyears away would nowadays be a part of ours. There may be legitimate reasons to set up a few colonies, such as backups in case of solar-system scale catastrophes, but by the time you've expanded out even just 100 lightyears (0.0001% of the galaxy), there are already tens of thousands of systems in your "empire". Of course civilizations don't need to act rationally all the time, even though they might derive no benefit they might do something just because they can. But how many times are they going to do this just because they can? 10 times, 100 times? 10,000 times? Eventually the novelty is going to wear off, and those massive quantities of resources being spent on these extremely expensive spacecraft are going to be repurposed for the betterment of the civilization.
Now let's say that, despite the extreme technical challenge of travelling more than a few tens of lightyears, and despite the complete lack of rational reason to do so, a civilization decides to just keep expanding anyways. Eventually they are going to encounter another civilization. This continuous growth is a threat to any other civilization - even if they agree to leave their neighbors alone, they are still ravenously consuming the resources in the area that such a civilization would want to have access to in the future. It is in their best interests to get the expansionist civilization to stop - possibly by diplomacy, possibly by other means. The expansionist civilization is squandering resources on its expansion, it's likely a young civilization that only recently developed the means to expand, its periphery is thousands of years less advanced than its core region and likely very underdeveloped, it has no means to move its assets to the periphery or concentrate its forces in the short term, and it has extremely long supply chains in the long run. Conversely the neighbors have been using their resources efficiently, they may have been around for a very long time, and they are operating close to their core region. The expansionist civilization will get in a fight eventually, and it will lose. Even if it doesn't get defeated so utterly that it is forced to stop expanding, eventually it will just encounter another civilization that will stop it from expanding.
The only scenario where continuous expansion is possible without FTL travel is if one of the very earliest civilizations in the universe has an inexplicable drive to expand and does so fast enough that no other civilization can arise fast enough to snuff out all possible competing civilizations in their infancy. That we have reached this point in our technological advancement long before a non-FTL civilization could expand throughout the visible universe strongly suggests such a scenario is impossible.
[0] Some people may feel inclined to bring up Von Neumann probes - craft which travel to other star systems, repilicate themselves several times over, and then launch more such probes to more solar systems, thus allowing for exponential growth. This technology doesn't actually make expansion any faster though. Building a probe at A, sending it to B, where it builds a second probe, and then sending that to C will always be slower than building two probes at A and sending one each to B and C directly. There is also no benefit to longevity - building a new probe is equivalent to replacing every component of the original.
That’s if civilizations even live that long in the first place.
Kinda comes to calculation that when earliest potentially space faring civilisation runs out of their sun? And can't adapt to live in system. For us that would still be at least few billions of years if not more with proper preparation.
And probably getting smaller every year. We don't have as many giant multi-megawatt radio transmitters as we used to. Quite conceivably it could be ~zero in a few decades, as everything goes fibre and cellular.
It takes a lot of power (or a highly directional antenna) to send a detectable signal detectable light years away. The only unintentional signals we generate are high power weather and military radar. Those are very tight beams that sweep the sky. Any interstellar eavesdropper would need to have the beam sweep over them to detect it. Even then it would be a transient signal with no guarantee of repetition since everything is it motion.
It would be like us being a mile apart in the blackest of night and you swinging a laser pointer around. Even if I'm looking specifically for you and have a general idea where you are the odds are vanishingly small your laser pointer will happen to be visible to me. You'd have to be specifically pointing it at me to even have a hope of me seeing it.
We could blast radio waves with ABBA songs into space to find whether there are other Swedish-speaking civilizations, or whether we are alone in the Universe. We don't because it's silly to think of the Swedish language as a necessary step for "advanced life".
Why do we think that human-like intelligence is special?
It's only futile to blast ABBA songs (or other human-like signals) into space if we think human-like intelligence is special.
It's precisely because we believe human-like intelligence is _not_ special that blasting (or listening for) space signals makes any sense. The assumption is that other civilizations will converge on some of the same technology that we've developed and recognize a patterned signal when they see one.
Why would anyone think that?
No other species in the history of the Earth has the ability to create human languages. Nobody outside the tiny group of 0.1% of humanity can speak Swedish. No single rock we've observed outside our planet can even understand the concept of a word like "Läderlappen" or "Knullruffs".
Those 10 million people are alone in the Universe as developers and speakers of Swedish just like these 7.9 billion people are alone in the Universe as developers and users of human-like intelligence.
Blasting signals into space is the same as singing ABBA songs really loud: maybe a sci-fi civilization of Klingons who speak a Swedish-like language could understand it, but in our Universe there's no chance that some extraterrestrial thing will converge on the same languages or technologies as we did.
The other issue is that it’s not clear how long technological civilizations last. We might be close to exhausting our own planet just 150 years after the invention of radio. Maybe technological civilizations bloom in the dark like beautiful flowers, then burn out quickly before they can spread to other systems.
First of all, we are talking about predicting the actions of superintelligent aliens. We aren't talking about slime molds or a bacterial infection, but beings with more intelligence than us, like orders of magnitude more complicated reasoning processes. They are effectively unpredictable, because if they weren't, wouldn't we be just as smart as they are? That level of intelligence comes with new levels of reflectiveness that are frankly not accessible to our weak brains. Like, maybe after reaching the next level of enlightenment, they decide that expansion throughout the universe like a worm is not actually what they want or that is what is good for the universe? Maybe they decide to rather study the universe and not interfere, the way biologists study, say, apes, without wanting to disrupt their natural behavior with their presence? Or maybe superintelligent beings find a way out of our universe, and pass into another dimension (cyberspace? black holes? disappearing through quantum foam? heaven?). Or maybe something else insane happens, like being superintelligent inevitably makes you completely terrified of everything, because you realize how powerful other aliens are and your calculations unequivocally show it's safer to stay at home and fart around doing the super-intelligent analog of baking chocolate-chip cookies? Not being superintelligent, we are like ants trying to contemplate human civilization. We have no context or experience, and we simply don't have the mental capacity to even imagine what we don't know.
Second, these probabilistic models are so fundamentally stupid. It's impossible for us to reliably estimate the probability of any event that's happened only once (without reasoning about the process that gave rise to that event), as we cannot estimate posterior probabilities without lots of samples. And humans on Earth have a massive chain of single-occurrence events that all seem to be absurdly improbable. Besides that, and perhaps even because of that, it's not even a foregone conclusion that our universe even selects from the middle of the distribution (i.e. is not biased). We could perfectly estimate the shape of a probability curve and yet live in a universe that stubbornly selects from the end of the distribution, all the time. All of our math could be totally right, but crazy shit just keeps happening.
Third, the anthropic principle is a total bitch. It means that we will never be able to estimate probabilities of events that were required to create us, because no matter how improbable they were, if they didn't happen, we're not even here to argue about it. If there are infinite universes (a multiverse, see Tegmark), then forget this whole mathematical sophistry, because then there is no need to live in some "average" universe; we can easily live in some stupidly improbably snowflake universe that has the 90 trillion improbable things that make apes possible; infinity doesn't care.
Coming to conclusions/guesses requires starting with some assumptions about about how the universe works. It's important not to lose sight of those assumptions and very important to have a discussion about how likely each assumption is to be true. So to the extent that anyone is saying "this is definitely how the universe is", I wholeheartedly agree with you.
However, it feels like you're being a little too epistemically nihilistic here. This kind of speculative work always starts without confirmation or any particular reason to believe it beyond how well it matches the curve it was fit to.
To quibble with a particular, this work doesn't attempt to predict the actions of super-intelligences, it's not making the claim that most civilizations will be "grabby", it's making predictions about what will happen under the assumption that some subpopulation of them decides to become grabby.
Here's what I mean. What makes the lights on your router blink? Usually, it's packets going in and out. At a coarse level, if your computer is doing something on the internet, the lights are gonna be blinking. But now increase the resolution, from seconds, to milliseconds, to microseconds, to nanoseconds. At a nanosecond level, whether the LED is on or off depends on whether a packet is going over the wire right this nanosecond. Whether a packet is earlier or later by a nanosecond is influenced by a bazillion variables: the router's internal state, its own operating system's scheduling, whether the devices connected to it are sending packets at it, dragging in their state, their scheduling, their programs, packet queues, etc. Gigabytes of state, changing nano-second to nano-second. Oh, and it's connected to the internet. When does the internet decide to send a packet to this router? If those are faster or slower by a nanosecond, it could be due the state along the entire path, all of which are servicing packets from all over the place, decided upon by super-complex distributed systems--datacenters full of them. So even the blinking of a router LED is connected to a supremely complex causality tangle. To understand the blinking nano-second to nano-second, you basically have to replicate the details of the entire internet. So, if I were to ask you instead to predict what will happen tomorrow at 3:33am--will your router be blinking, let's say, fast or slow? Who knows. A DDoS might crop up because someone was mad at Amazon, or maybe your OS downloads a software update, or maybe you are up watching Netflix, or maybe the whole thing is down because nuclear war. It's progressed so far from a simple bell curve that probabilistic reasoning, I would argue, is useless. And that's just without the internet being "intelligent"! Now assume the internet knows this prediction game is afoot, and it gets to bet too. The whole thing goes off the rails.
No, we can't predict what aliens will do. This paper is a mathematical exercise that might apply to bacteria or video game characters, not interstellar civilizations.
That's my take, they wrote it better though. That section is short, straightforward, and worth reading.