Humanity survives long enough to create a Dyson-Ring around old Sol using many of the planets and asteroids currently in the system. Then 'something happens' we die out, we discover a way to travel to other stars, something.

The ring will have some automated systems such as keeping the sun centered in the ring and some capabilities for self repair to critical functions.

While making the ring we made biomes all over the place as zoos/preserves for most of the plants and animals still living on the Earth. (And we captured as much DNA samples as we could get for general knowledge to allow us to bring back different species should we feel like it).

Even though they are 'zoos', they are mostly left for nature to take its course, herbivores feeding on plants and carnivores feeding on herbivores etc.

Now, most of the systems are just to keep the basics running, not to repair a large hole caused by an impact of an asteroid or what ever (though most have been consumed in making the ring).

Could the Ring last long enough to allow an intelligent species to evolve with similar mental capabilities to humans? Or would it just crumble into an asteroid belt? (We accidentally killed off the other great apes, and hadn't gotten around to reintroducing them).

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    $\begingroup$ Take your pick: Cephalopda, psittaciformes, cetaceans, canids. All have a chance to make that next leap. Will any make it? Gut reaction: way too many variables to be able to determine. $\endgroup$ – cobaltduck Apr 4 '16 at 15:12
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    $\begingroup$ Definitely related, not a duplicate: How fast could a directed breeding program turn another Earth species intelligent? The answers to that question would seem to establish a lower bound for how long the Dyson sphere would need to survive for this to happen. $\endgroup$ – user Apr 4 '16 at 15:20
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    $\begingroup$ A "Dyson Ring" is not one of the varients. Did you mean a Niven-style ringworld? $\endgroup$ – JDługosz Apr 5 '16 at 1:35
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    $\begingroup$ There is literally no possible way to give an answer that's not wild speculation: You asked if it's possible for multiple random and rare events to align. Sure, if you want it to for a story. $\endgroup$ – The Nate Apr 5 '16 at 5:05
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    $\begingroup$ Re opinion based: and to keep it in line with the answers already given, instead of asking "can it?", change the Q to "what would be necessary to...". How long would we need it to last, and what issues would allow or prevent that? $\endgroup$ – JDługosz Apr 5 '16 at 13:32

Yeah probably it could survive long enough since a civilization advanced enough to build a Dyson ring will have automation, self-repair and materials science capabilities far beyond our own. Also, given the immense surface area of a Dyson ring, a local extinction event would still leave immense portions of the sphere completely habitable. And, with the Oort Cloud and Kemper belt cleared of objects (potential impactors), there's not much left that can pose a significant threat to the Dyson Ring. I'm assuming that any rogue planets have been detected and used as well. Other than ionizing solar winds and solar hard rad, what threats are left? Any civ that can build a Dyson ring will know how to protect their investment and prevent it from falling apart any time soon.

Let's be clear here, no one knows for sure all the ways that intelligent life can evolve. We only know the monkey route, on earth, post-dinosaurs. For the one example we know of, the monkey route took about 60 millions years in order for primitive mammals to evolve from the trees to full tool-using bipedalism. Perhaps a different set of environmental pressures will lead to human level intelligence in a few million or a hundred million.

  • $\begingroup$ He's not asking about a Dyson sphere. Without knowing the proper kind of structure and details about it, how can you say how long it will last when the builders have abandoned it to nature? Counterexample: it lasts 10 years after they leave, since nobody with command authority is present to authorize critical decisions. $\endgroup$ – JDługosz Apr 5 '16 at 1:39
  • $\begingroup$ @JDługosz thanks for correction of sphere to ring. I was making no assertions of how long the ring would last, only how long it would need to last for humans to re-evolve from primitive mammals. I have no idea how long a structure like that would last. $\endgroup$ – Green Apr 5 '16 at 1:43
  • $\begingroup$ There's two assumptions in this answer: super technology lasts super long without maintenance, and evolution eventually spits out intelligent life. The former is demonstrably false, modern technology is increasingly fragile and nature is relentless, you'll have to explain why this trend will change. The second, there is no "longest time" because we have no idea whether evolution produces intelligence or intelligence is a fluke. $\endgroup$ – Schwern Apr 5 '16 at 2:34
  • $\begingroup$ @Schwern there are examples that can go either way in terms of "proving" technology is more or less fragile. Frankly, I'm very happy with the chromium/iron alloys that last an incredibly long time without corrosion. That's modern tech. I believe that Humanity is finding the places where it makes sense to have things last a long time and the places it isn't. And you mean to tell me that the tech of today will have any bearing on the tech capacity of a Dyson ring building civ? We shall differ on that point. $\endgroup$ – Green Apr 5 '16 at 3:07
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    $\begingroup$ @Schwern 60 million years was how long it took last time to evolve humans from basic mammals. Without additional info (which I'm not sure the OP can provide with sufficient detail), it's impossible to say whether human level intelligence would, for sure, evolve again. In light of that absence of detail, all I can do is cite how long it took this time and assume that a similar period would be required again. $\endgroup$ – Green Apr 5 '16 at 3:10

Given that a rigid Dyson structure doesn't work by known science, who knows?... but probably not.

To make a stable, rigid Dyson sphere or ringworld work around a star you need not one, but MULTIPLE sci-fi engineering elements.

  1. How does it remain stable around the star?
  2. How is there gravity on the surface?
  3. (A ring special) How is the atmosphere kept from falling over the edge?
  4. How does it keep from collapsing on itself?
  5. Where do we get the material?

If we don't know what it's made of, what's holding it together, what's holding it in position, or how things are held onto it, then it's so divorced from reality that any prediction about how long it will last without maintenance is as correct as any other. Maybe with some of those holes filled in a prediction could be made, try another question with more detail?

Then there's the second part of the question: how long does it take to evolve an intelligent species from the greatly culled gene pool that's left in future humanity's zoos? Again, the answer is who knows?... but probably 10 to 100 million years if it happens at all.

We only have one example of an intelligent life form evolving naturally, humans, so it's hard to extrapolate from a single data point.

Depending on where you start you get a number anywhere from the evolution of primates 85 million years ago to Homininae 14 million years ago to Homo 2.8 million years ago.

There's nothing about evolution that says it leads to intelligence. Intelligence might be a fluke, a terrible survival strategy, and evolution is done with that. In that case the answer is "never".

Another way to approach the question is from an engineering/cost POV.

Engineering is a trade off between features and cost/time. Given the immense difficulties of building a rigid ringworld, why would the engineers add to the problem? While automatic maintenance and repair systems will surely exist, why would they over-engineer them to work completely autonomously for millions of years? There's no human need for this.

As an example, surviving ancient structures have lasted not because the builders wished them to, but because they are very simple, their materials are very durable, they have no moving parts, and they got lucky. A pyramid is the shape a pile of stone naturally makes. Most everything else they made is gone, we see what little has survived. Even then, they've only had to last a few thousand years. In a million years all of humanity's structures will be gone.

Which is why I say the answer is, even knowing nothing about their technology: probably not.

Humanity would more realistically create a Dyson swarm which, if they got the orbital mechanics right, would last pretty much indefinitely.

Here is my "clever" answer: immediately. The new life is the AI necessary to maintain the ring.

Many people have been arguing in the comments that it will have auto-repair and maintenance technology (agreed) which will, unattended, keep everything working and hold back nature for the millions of years necessary for life to evolve (nope) even though it was never designed to do so because it was never a design requirement. It would have to somehow improve itself...

The builders made themselves an AI, or near enough that, left unattended, it achieved enough intelligence to adapt and survive. That is the new life which appears on the ringworld.

It's a feasible extension of the design requirements: the designers would need a very smart machine to run the infrastructure. Its AI scoring algorithms would be to maintain the ringworld in a stable configuration. The human builder could even be routinely holding it back from becoming too advanced. Once the human restraints are gone, and with the additional pressure of having to now do everything itself, a ringworld-sized computer could evolve in a matter of minutes once it's allowed to go rampant to achieve its goal.

It could even have wiped out the builders, if you want to go that route.

  • $\begingroup$ You wouldn't want the thing you're living on to require much maintenance. Certainly not frequent. It could take months in high-tech transport (short of FTL) to navigate to the far side of the ring to fix a damaged external system. Crap happens. Far as I'm concerned, the engineers haven't solved the problem until they have automated it well enough to last at least years without any intervention---preferably millennia. $\endgroup$ – The Nate Apr 5 '16 at 5:20
  • $\begingroup$ @TheNate I agree, maintenance is important. And you bring up a good point about how long it takes to get from one side to the other (186 million miles in a spaceship, 292 million by land). We can even go as far as thousands of years waiting for a delivery from an interstellar civilization. But 1) why would it have to work with no humans present at all and 2) why for the millions of years it would take to evolve intelligent life? $\endgroup$ – Schwern Apr 5 '16 at 6:28
  • $\begingroup$ Why no humans? Because something could wipe out whoever is supposed to handle this and you'd need time to get there to fix it. As to millions of years, I don't know. Not arguing with your answer, just pointing out some sticky bits. I will point out that, theoretically, starting from chimps cuts development down by ages and that the improbabilities could happen early as easily as late, too. $\endgroup$ – The Nate Apr 5 '16 at 6:58
  • $\begingroup$ I think, rather than asking why it would continue to work without humans present, it's more pertinent to ask why it would stop working, just because there's nobody around. That's a huge reason people automate things in the first place: to take care of stuff while we're not around. It's easier to give the directive, "Keep things maintained as specified," rather than, "Keep things maintained as specified until [arbitrary date]." Without people to shut down the maintenance infrastructure, I don't see why it wouldn't just keep going indefinitely, if engineered to be self-repairing as well. $\endgroup$ – Magnanimancer Apr 5 '16 at 12:48
  • $\begingroup$ @Magnanimancer It stops working because stuff wears out and nature eventually wrecks everything man-made, even if it tries to repair itself. One could say they have auto-repair tech that will just keep working forever, but we have nothing current or projected that can do that for thousands, let alone millions, of years. This is where it diverges from "science-based" into "science-magic". You could answer "nanobots" but it may as well be "pixie dust". Even nature can't do it! And it's not a design requirement, you propose it's an incidental part of the design that it lasts forever. $\endgroup$ – Schwern Apr 5 '16 at 16:25

The threats to such a ring would be minor. You'll need a lot of mass in order to build it, what's the most convenient source? All the bodies of the star system. There won't be any rocks left to threaten it, the only threat will be stuff coming in from interstellar space--not a serious threat in the timeframe you need.

On the other hand, a hit would be far more catastrophic than other posters are envisioning. Consider Larry Niven's Ringworld--the problem from the hit it took was that it punched a hole in the floor and the air would drain out. To make it far worse his system was based on a super-strength material, if we are limited to what chemistry actually permits you're stuck with having it ride on a truly massive track. Oops--that rock just punched a hole through the system that keeps two parts separated by mere inches when they have a relative speed of about half a percent of lightspeed.


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