This kind of assumes that a “maxed out” civilization can expand at speed of light, but I don’t think it is given. It may very well be that meaningfully massive transport cannot exceed even a small fraction of <i>c</i>. After all, propulsion has to make energetic sense.<p>1. There is energy to get to speed<p>2. Mass of fuel to decelerate (and you have to accelerate that fuel in the beginning!)<p>3. Highly blue shifted CMB (that alone limits how close to c you can get before becoming plasma)<p>4. Collision with micrometeorites (so the “ship” has to be microscopic or probability of collision quickly goes to 1, and there is no way to survive even micro collisions while moving at c).<p>5. Limits on how fast you can give impulse (because your ship is made of matter with finite strength). Eg You cant reasonably railgun something to close to c without converting it to plasma.<p>There is also all the things you do when you get somewhere before sending more probes to expand, presumably it’s not a single location that seeds everything else (and if it is then the energy budget of that is also complicated).<p>Now, even at 0.1 <i>c</i> and with many pauses to replicate on the new worlds it would still take only a few million years to span the milky way, but if someone was mid-expansion we would see them way before the bubble hits. Being limited to 0.1c also means that those not in our galaxy will likely be unable to expand into ours (and vice versa).
An interesting paper that I don't see brought up often enough is "Dissolving the Fermi Paradox" by Anders Sandberg, Eric Drexler and Toby Ord[0]. They show that it isn't a surprise that we are alone in the universe if we consider the uncertainty inherent to parameters of the Drake equation. Their analysis estimate that there is (at least) a 39% chance that we are alone in the observable universe.<p>[0]: <a href="https://arxiv.org/abs/1806.02404" rel="nofollow">https://arxiv.org/abs/1806.02404</a>
Another interesting idea I've been playing with is that <i>there's no guarantee that the lifeform that replaces us will be the same level of complexity</i>. What does it feel like to be a molecule? A mitochondria? A cell? All of these are or were once self-contained "things", but now they exist as part of larger systems. Our image of the beings that replace us tends to look like us and be roughly the same size - robots or little green men. But what if the thing that replaces us <i>encompasses</i> us, so that individual humans become cells in a giant superorganism.<p>There's some evidence that this is already happening - with 6 billion humans on earth, the global economy is already showing specialization (similar to how cells develop into organs in a human) and complex emergent behavior, with parts of it dying off without killing the whole.<p>What if the reason are experience looks like it does, with life a full 1/4 of the age of the universe, because at later points in the universe's evolution, life at this scale becomes meaningless and the primary sentient beings are planetary civilization interacting at the speed of light through the galaxy? Or galactic civilizations interacting throughout the universe?
It seems like the argument gets a lot less interesting if the most-expanding interstellar civilizations don't spread at anywhere near the speed of light?<p>It's easy to think of reasons why this might be the case. There is acceleration, deceleration, and replication time, which seems like it would be substantial for any civilization that doesn't want to put most of its resources into replicating as fast as possible.
I like to imagine that this is how things would look if we entered a Karadashev type III civilization's light cone:<p>One day, in a small quadrant of the galaxy, we'd notice starts "shutting off", simply going dark. After a few months, our astonomers would confirm their new model: the amount of stars going dark is increasing. Days later: the rate of increase itself, is increasing.
One day we'd wake up, and a small portion of the night sky would be dark. A disk of darkness, right at the brightest part of the galactic plane. By then we would have figured it out of course: most stars in the galaxy were being turned into dyson spheres. They were spreading almost as fast as light, making it look almost instantaneous, even though the process had taken hundreds of thousands of years. In a few thousand years a large portion of our sky would be dark. And after that...
The ideas discussed in his post, especially the idea of rapidly expanding spheres of civilizations consuming all resources in their path, were beautifully explored in Stephen Baxter's sci-fi book, Manifold: Space (a spin-off of his earlier book, Manifold: Time, which is also excellent). In his book, alien intelligences are common; once they become sufficiently advanced, their civilizations tend to rapidly expand and consume all available resources, often to the detriment of other civilizations in their path. This pattern leads to some interesting phenomena: first, while the night sky might seem quiet at first, once we do encounter aliens, we tend to see their signals across many star systems in rapid succession. The reason is pretty obvious: there is only a brief period of time when we are on the surface of a sphere - a few years after our first observations of aliens, we are engulfed within their sphere and observe their signals from all over our stellar neighborhood. Another idea he plays with is the idea of "refugee" species, who attempt to flee oncoming spheres by evacuating ahead of their path instead of being consumed.
Actually, he pushes this idea even further: in the book, our solar system was already engulfed in a few spheres millions of years ago. He suggests that this why Venus is such a hellscape: the aliens came, took the resources they wanted, and left behind a polluted mess. In the case of Venus, they left lots of greenhouse gases behind as the result of some chemical process used to extract resources; as a result, Venus quickly became the warmest planet in the solar system. It's a fun twist on the Fermi paradox: signs of aliens are actually all around us, we are just too dumb to notice them.<p>Another interesting idea he explores a bit is "ownership" of resources. Do the resource-rich asteroids in our solar system really belong to us? Or are they available to any alien race who happens to pass through? In the book, we first notice aliens by observing unexplainable infrared radiation from the asteroid belt (later revealed to be thermal emissions from their resource extraction). He suggests that these aliens will potentially crowd out humans; even if they are not overtly hostile, they could gobble up all the resources we would have used to expand our civilization.<p>Highly recommend this book.
The site appears to be down. (504 Gateway Timeout) <a href="https://archive.is/ki5Vm" rel="nofollow">https://archive.is/ki5Vm</a>
<i>Notice that, in Robin’s scenario, the present epoch of the universe is extremely special: it’s when civilizations are just forming, when perhaps a few of them will achieve technological liftoff, but before one or more of the civilizations has remade the whole of creation for its own purposes. Now is the time when the early intelligent beings like us can still look out and see quadrillions of stars shining to no apparent purpose, just wasting all that nuclear fuel in a near-empty cosmos, waiting for someone to come along and put the energy to good use.</i><p>This presumes that The Most Technologically Advanced Civilization sees virgin nature as nothing but raw material waiting to become something useful. That's possible, but <i>probable</i>? I think that it's likely that diminishing marginal utility still holds even for TMTAC, and therefore they are disinclined to convert all the universe's visible matter and energy into Dyson swarms of Space Product.<p>My favorite (not particularly testable) solution to the Fermi paradox is that TMTAC originated shortly after the first heavy elements and planets formed. It became space faring and expanded throughout the visible universe before our solar system formed. Its agents have been lurking in our solar system since before life first appeared here. Having long ago achieved immortality and technological supremacy, there's no motivation for plundering <i>or</i> trading with terrestrial creatures. They silently observe like space faring bird watchers. They'll intervene if/when we start to approach the capabilities of TMTAC, particularly if we show destructive paperclip-maximizer inclinations toward converting the universe into Space Product.<p>To borrow some terminology from Nick Bostrom's <i>Superintelligence</i> book, it's possible that the universe has been colonized by a <i>singleton</i> civilization -- the first one to become star faring. But it's not particularly chatty or inclined to let potentially competing star faring civilizations expand.
How a civilization would expand at the speed of light? Unless it lives directly on the fabric of space or something like that, matter is discrete in the universe. You settle on planets that are not everywhere, or in space stations built with Oort cloud or asteroid belts materials, but it takes time to settle and expand in each new ground you get. You are not talking about the speed of light anymore there.<p>Of course, here I'm trying to think like an alien civilization that is far ahead from us in technology and scientific knowledge, besides having an alien way of thinking, but the same goes for the article.<p>In any case, if that is like any disaster spreading through the universe at the speed of light (big rip?) not only we won't have time to notice, we won't be able to feel the effects neither.
This is extrapolation from an extremely small set of facts, and tremendously conjectural assumptions. It’s the kind of thing you might expect to see from a person living in a civilization that just discovered electrons 200 years ago. Come back to me in 100 years once the economy and population has reached some kind of steady state and then let’s revisit some of these claims.<p>A lot of what we think is rational discourse is actually ingrained, unspoken ideology floating to the surface and being coated with a patina of post hoc rationalization. That’s why it’s so hard to do science properly, especially social science- people don’t even know that they have biases, let alone what they are. But biases aren’t something you can point at directly and say, this belief is not true, it’s more that you might be overestimating the probability of truth of a whole bunch of little things by 10 percent and that creates a self reinforcing network of probable facts that adds up to weird beliefs when they are all put together.<p>The author of the article believes on some deep level that progress is inevitable and will go on indefinitely, combined with the unconscious imagery of a lifetime watching science fiction films, and a life of watching progressively more impressive gadgets appear on store shelves. It all adds up to essays like this.
Or... is it possible that we are not supposed to meet the "others?<p>Consider:
If you wanted to build a "terrarium" for sentient evolving life forms how would you keep them from escaping?<p>1. Make the distances really really big
2. Put a speed limit in the environment<p>Rolled up with the Fermi paradox this simulation has "smelled fishy" to me for some time. :)
Below [1] Hanson explains some of the details of the argument in length.<p><a href="https://www.youtube.com/watch?v=Rjm--7t8Llk&feature=youtu.be" rel="nofollow">https://www.youtube.com/watch?v=Rjm--7t8Llk&feature=youtu.be</a>
Huh?<p>> Only when the sphere’s thin outer shell had reached the earth—perhaps carrying radio signals from the extraterrestrials’ early history, before their rapid expansion started. By that point, though, the expanding sphere itself would be nearly upon us!<p>Wouldn't the problematic portion of the sphere be, by definition, millions of years away from us? Given that radio waves travel at the speed of light, and the alien civilization travels at slightly less than the speed of light, it seems like we should have at least however many million years it took for those aliens to get from producing radio waves to "maxing out" travel.
Interstate idea. The title overstated too late though.
Following the premise that an expanding civilization is expanding near the speed of light and it's radio will reach us first.
We can expect hundreds of years between radio and anything physical.<p>1)
We started producing a lot of radio around 100 years ago.
And we are still a long way from expanding at near speed of light. Even with expodential growth in capacity.<p>2) expanding near speed of light is much less than speed of light.
Say 99% of the speed of light. And expanding civilization is probably going to be coming from far far away, just because there is a lot more far far away than pretty close.
So say they are comiy from 10,000 light-years away (still close by galactic standards, and incredibly Close by Universal standards). Then the radio they start transmitting when their grown begins has gained on their expansion ba lead of 100years by the time it reaches us<p>Sure on the million and billion year time-scales mostly talking about that 100+ years is very little but it is still generations.
This seems like a variant of a hypothesis I've heard before: "The universe is old enough, and the rate of expansion of a spacefaring civilization is fast enough (relative to the age of the universe, even at sub-light speeds) that either the aliens should already be here since long ago, or we're the first (or among the first)." ?
This may be beside the point, but I don't think there is any alien lift out there. I am going to make up number N_life_universes which is the number of universes needed in order for an instance of intelligent life to evolve. Many people seem to assume this much less than one. I think it is much greater than one, meaning most universes you look at will be void of life. I'd also say there are many universes, one source being the rules of quantum mechanics. But I know some people believe in wave function collapse, and if that is true I am not sure what this means for having mulitple universe.<p>There is a related number, N_hamlet_universes. This is the number of universes needed in order for monkeys to type Hamlet typing as fast as they can, covering every planet spaced 6' feet apart (in case one gets sick). I think this is also a very large number but I haven't figured it out.
For a long time I've figured that the Fermi Paradox is not much of a paradox.<p>Open question: Are we likely to be able to detect the difference between large asteroids and a small swarm of habitable environments in a star.<p>And the second question is: Is it worth spreading out? An advanced civilisation can defend against or modify (maybe even focus) the damage that an imploding star would cause, and an Issac Arthur video on the topic of the amount of space we have in the solar system states clearly that there's more than enough for trillions of trillions of trillions of habitats. There doesn't seem to be much reason for spreading a civilization out whatsoever, given the cost of communication and the assumed cultural and informational lag between the settlement and the source civilization.<p>As the article states, it's unlikely to be the case that we see an expansive civilization until it's too late.
I have not studied this area of science but the article reminded me of the fictional book series The Three-Body Problem by Liu Cixin.<p>I really don't want to say anything to spoil the books but the series were so good that I devoured them last summer which is something I rarely do.
We're just not looking hard enough. It might seem like a ton of money has been poured into it, but space tech and especially monitoring is so underfunded that it could be a joke when compared against anything else.<p>Any entertainment industry on its own has more funding than all of humanity's space pursuits. All the apps for tracking time, buying clothes, losing weight, scanning tomatoes, properly wiping, get more money than the ESA or JAXA (at least NASA has more than them heh).<p>All the speculation and dreams of a great space colonization are nice, but the reality is that most of us will die on this planet, and likely take half of the life on it with us.
If you look carefully enough at the implications of our situation through the lens of the 2nd law of thermodynamics,
the Fermi paradox becomes a lot less paradoxical.<p>Edit: Apparently I have violated a HN taboo in even daring to mention that bothersome little law.<p>Understanding it and its implications and applying that knowledge to our IRL situation on earth might not be fun, however IS fundamental to making plausible statements about perpetual motion and related topics (i.e."von Neumann probes.")<p>Now, all that remains to be seen, this being HN, is:
Will this comment be downvoted into oblivion without a good reason being proferred?
This is the most profound thing I've read in a while.<p>I'm tempted to whip up some numerical simulation to verify this to some extent...<p>> But here’s the interesting part: conditioned on all the steps having succeeded, we should find ourselves near the end of the useful lifetime of our planet’s star—simply because the more time is available on a given planet, the better the odds there. I.e., look around the universe and you should find that, on most of the planets where evolution achieves all the steps, it nearly runs out the planet’s clock in doing so.
We don't see aliens because we are looking wrong. They're probably <i>right there</i>.<p><a href="http://cantrip.org/slow.pdf" rel="nofollow">http://cantrip.org/slow.pdf</a>
So in any case I agree that the world needs to get its shit together and thinking about it: I have never really considered to give it a serious try to make/contribute to make that happen.
Analogy: humans have existed for something around 100,000 years, yet we only explored the whole ball - and began affecting it to the point of worrying about making it uninhabitable - within the last few decades. Any lesser culture/species was dominated or destroyed before they could come to grips with the expansion ... not so much because of malice as of “bug vs windshield”.
This sounds like the grey goo problem [1], but at a cosmic scale and at (near) the speed of light.<p>Like other commenters have already said, this scenario assumes that near-speed-of-light travel is workable.<p>[1] <a href="https://en.wikipedia.org/wiki/Gray_goo" rel="nofollow">https://en.wikipedia.org/wiki/Gray_goo</a>
Even if we do have young competitors like us, they could still be millions of years older than us- the blink of an eye, in a planet’s lifecycle.<p>But millions of years of technological evolution is plenty enough time to make grey goo (or light speed spheres of incoming civilization).
Even in case #3, is it reasonable to assume that the aliens would expand in 3 dimensions at the speed of light?<p>And even of that is true, wouldn't we expect a significant fuzziness in that on the order of a millenium, where we see signs but haven't yet been engulfed?
Hubrisimus. Our current models are the most useful ones we have that fit our limited dataset, but we have no clue whether we understand the first thing about space and time and the age and size of the universe(s).
Robin Hanson is a pretty decent high-concept sf author, and his occasional forays into cosmic horror can be enjoyable too. It's just too bad he ended up in the wrong line of work.