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Comment by Semirhage | Hacker News Reader

If advanced technological civilizations are on average, short-lived, then the separation could be orders of magnitude smaller and your point would still stand. All of human evolution is in the millions of years, modern civilization in the thousands, technology in the hundreds.

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This seems to me to be the most likely scenario given what we see here on earth. Our civilization figured out how to remove limits on its growth a lot faster than it is figuring out that we need to self-impose limits on our growth in order to avoid a catastrophic failure of our ecosystem. I see no reason to expect anything different. Evolution does not plan ahead.

> faster than it is figuring out that we need to self-impose limits on our growth in order to avoid a catastrophic failure of our ecosystem

We "figured out" unconstrained growth could be catastrophic a couple of hundred years ago at the very least. And in fact we guessed prematurely as technology extended the date of the catastrophe multiple times.

So we then bounced into a phase of overconfidence whereby some of us decided that technology could overcome all problems.

(Arguably we are still in this phase - or at least some of us hope this turns out to be true as we've lost hope in the possibility of political solutions to problems caused by growth)

Yes, I think you have this exactly right. We've dodged the bullet for a few hundred years, which our brains are predisposed to think of as a long time. Then we (well, not all of us, but enough of us to matter) (mis-)apply inductive reasoning and conclude that because doomsday predictions have always been wrong in the past they will continue to be wrong in the future.

In fact, you can sum up the problem as a pithy slogan: Doomsday predictions are always wrong. Until they aren't.

Someone should make T-shirts.

Given enough civilisations, it's likely that a few will eventually manage to not wipe themselves out (at least for long enough to become fairly redundant).

Yes. The $64k question is: how many is enough, and do we actually have that many close enough in space and time that it matters?

Exactly, and how many want to be found, or find other species? Of those, how many are so far away that communication is a pointless enterprise? Not to mention that the more difficult and costly communication becomes with distance, the further out in time you are. All in all, using a ton of high tech and energy to say “hi” to us from 10,000 ly away and 10,000 years of time seems... weird. At 100,000ly it starts to be a really exotic proposition, and at a million ly you shouldn’t assume your message will even reach the same species.

Unless your fellow technological life is within a few hundred light years, communication of any kind starts to look like throwing messages in bottles. Of course the closer your target is, the less wistfully academic it is. If Proxima Centauri had a planet with a civilization like ours, you’d have to consider what they could do other than just talk. At that point, the issue switches from insane time scales rendering the whole process moot, to potential forms of dark forest detente.

I originally saw this proposition on reddit - if all humans died where they stood right now, what archaeological evidence of our civilization would exist in 65 million years? 200 million? 350 million?

The discussion at that time assumed vanishingly little would survive that long - potentially just a thin layer of radiation from atmospheric nuclear testing that would be hard to place in time with accuracy more than +/- a couple million years.

I say this more as a thought experiment than a serious suggestion, but if a "technologically advanced" civilization did previously exist on earth, 100+ million years ago, what evidence of it would we expect to find at this point?

This is actually the setting for a sci-fi story I want to write. There's no reason to believe that the dinosaurs didn't have some kind of civilization, because we are so far removed from their extinction that any artifacts would be long gone. Unless they went to space, and the issue there is there's a whole lot of territory.

The rapid spread of animal and plant species around the globe when there wasn’t a supercontinent might be visible in the fossil record. We’d be a crank answer to the “How did potatoes spread from the Andes to the rest of world?” problem.

The arc of technology is significantly longer than 1000 years.

The arc of technology that would matter or be detectable to a distant civilization is less than 200 years of our history so far. It is yet to be seen how far that arc extends to the future. Even if it does, we’ve already passed the peak of our broadcasting in the EM spectrum. It’s not hard to imagine us coming to terms with the speed of light, and ultimately losing interest in stars that could only be reached by our ancestors tens of thousands of years from now. If we stick within a few tens of light years, and don’t bother to try and contact life we’d have to communicate on a thousand+ year “tape delay” we’d be hard or impossible to detect. That of course assumes that some other form of life is interested in something so far away and in its relative past.

All of that assumes that the arc of technology doesn’t terminate in a cosmic eyeblink after the current era, which it might. Either way, there is a sort of childish assumption that we’re always going to be as exploration-minded as we are today. If ‘c’ really is the cosmic limit, then it makes more sense to stick closer together, because any significant travel will imply either speciation, or a one-way cultural trip.

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