"Imagine the exotic "pollution" caused by civilizations which are advanced enough to tinker with the fabric of spacetime, but not advanced enough to understand (or care about) the long-term consequences of that tinkering"
That's fun science fiction, as others have pointed out, but in terms of real science, at the moment that's just a sort of subtle way of anthropomorphizing the universe and projecting human experience far, far beyond where it is applicable. Einstein's equations for spacetime evolution don't have anything that looks like "pollution" in them. There's no "stress term" for "space time that has been put through the wringer and is broken now". Black holes do not seem to leave "broken space" behind them or anything like that; indeed, "leaving broken space 'behind' them" would be an incredibly ill-defined term. In what preferred reference frame does your "pollution" take place in?
The only real concern is if there is some way to violate the conservation of energy, as real space does seem to do that at large scales at the moment. In that case someone might explode something, potentially large enough to make a mess of a galaxy or more. But we don't have even a hypothetical example of how to do that; just because the universe is violating energy conservation does not mean there's any conceivable organization of energy we can create that will do it, if the reason conservation is being violated is the injection of energy from some other effect or something.
"Your comment strikes me a bit like a chemist denying environmental pollution as it's all "just chemicals.""
Chemicals admit of a form of pollution when they form themselves in ways we don't like. Spacetime doesn't have that sort of memory, excepting exceedingly weak gravity waves, for which it is basically impossible for those to ever be your biggest problem (if not simply impossible for those to really be a problem). There's no spacetime equivalent to dumping a nasty chemical somewhere, and a hundred years later that chemical is still there hurting people. Spacetime doesn't work like that.
You're basically anthropomorphizing, thinking that there just has to be a way for humans to screw this resource up because humans are just that icky and gross, because cynicism and fashionable misanthropy. There isn't. Not in the real math. There's nothing humans can do in the real math that we know that the universe hasn't already done a couple dozen orders of magnitude larger than we could ever dream of. If space was going to "rip" or something, it would have already. It doesn't. In fact, in the real Einstein field equations, space very, very, very aggressively doesn't rip or suffer any other such problems. Any attempt to introduce such defects results in those defects immediately (and often quite energetically) undoing themselves. That's why when you read about real wormholes, for instance, the story always ends with the wormhole collapsing and exploding before anything, even light, could possibly traverse it.
Real math may change, in which case this answer may change. However, I expect that by the correspondence principle, even the ultimate unified theory of everything is unlikely to have an outcome where suddenly all this stuff is possible. Whatever the ToE is, it's still going to reduce to General Relativity in the large scale.
The pollution would be internal to the civilization, not something lasting of import to outsiders. The ability to warp spacetime to the point of violating causality, time travel, might be a death nail for a civilization. Literal prescience could be dangerous. As such technology moved though a society it could be described as a pollution.
Maybe such technology involves the creation of unnatural structures, something like stable wormholes on human scales. If those structures outlived their creators, areas of space containing them could be considered polluted, or at least dangerous to later civilizations.
Douglas Adams did some thinking on this for Hitchhicker's, that time travel caused cultures to stagnate and eventually degrade for lack of motivation.
> The ability to warp spacetime to the point of violating causality, time travel, might be a death nail for a civilization.
death knell
I know you probably know this, and I don't mean any disrespect. I'm writing this for other people who don't speak English natively (I'm also not saying you're not a native speaker, just that I'm not). I don't want anyone to go away with the wrong idiom.
"You're basically anthropomorphizing, thinking that there just has to be a way for humans to screw this resource up because humans are just that icky and gross"
I said nothing of the sort. You are, perhaps, confusing me with another poster.
"There's no spacetime equivalent"
Nonsense. The obvious example is emitted radiation, though any type of energy, matter or field byproduct might fit the bill.
Pollution is undesirable on earth because it causes us harm from which we can't escaoe or reverse.
The idea of "polluting" spacetime makes no more sense than humans "polluting" the natural organization of air molecules by displacing them by existing, or polluting the natural distribution of entropy by making decisions.
It's just bringing politics into a place where it doesn't belong.
Pollution is intimately tied to politics because most inhabited property is owned, which means it's regulated by some governmental systems having varying degrees of regulation and penalties for pollution. I have no idea why that has to be explained to you.
Being able to point towards a subset of pollution which is regulated does not necessitate the entirety of pollution as regulated/political. Pollution isn't defined by political fiat.
Your argument also doesn't hold considering that in the case we're talking about right now, the vast majority of spacetime is not inhabited nor is it regulated by anybody. Yet we're still able to talk about pollution because pollution in no way is tied towards a politicization of the conversation.
One could even go so far as to say you've polluted the conversation by including this "but you're making it political" distraction.
You admit space is uninhabited. Your unnecessary and petulant copy/paste of the definition of pollution includes the words "poisonous" and "harmful". Which isn't possible to do to an uninhabited area. I have no idea why you keep forcing such a contrived idea, other than to draw in a political "bad humans, always polluting" message. Anyway I'm done with this silly conversation. Have fun
Much of our terrestrial pollution took place in "uninhabited areas" which decades later became inhabited. Your comment is reminiscent of 19th and early 20th century attitudes toward pollution.
I'll acknowledge that harm and poison require a reference for where the harm is done, but I don't think it requires human interaction necessarily.
We are able talk about harm being done to insect populations or coastlines or any other inanimate objects. Again, humans, and their politics, aren't necessary.
I don't find my quoting of the definition as being petulant. I was wanting to frame the conversation around a shared definition of the word rather than asserting requirements.
Putting "pollution" in quotes was to substitute it for "waste", or byproducts, or side effects, that may or may not be undesirable for some species somewhere and somewhen.
I just imagine that once you do work at such scales, and with such strange materials and results, then the "waste products" of that work would be just as weird.
Also, would black holes not be considered "broken space" themselves?
"Also, would black holes not be considered "broken space" themselves?"
Even that is really an anthropomorphization. They don't "spread". They don't "damage" the space around them. They don't leave behind anything as they pass through space. They aren't having the effects that people imagine when they think about "pollution".
There’s no ‘nuclear holocaust’ term in the equations for atomic physics, but nonetheless it is an undesirable consequence of screwing around with nuclear weapons.
That's fun science fiction, as others have pointed out, but in terms of real science, at the moment that's just a sort of subtle way of anthropomorphizing the universe and projecting human experience far, far beyond where it is applicable. Einstein's equations for spacetime evolution don't have anything that looks like "pollution" in them. There's no "stress term" for "space time that has been put through the wringer and is broken now". Black holes do not seem to leave "broken space" behind them or anything like that; indeed, "leaving broken space 'behind' them" would be an incredibly ill-defined term. In what preferred reference frame does your "pollution" take place in?
The only real concern is if there is some way to violate the conservation of energy, as real space does seem to do that at large scales at the moment. In that case someone might explode something, potentially large enough to make a mess of a galaxy or more. But we don't have even a hypothetical example of how to do that; just because the universe is violating energy conservation does not mean there's any conceivable organization of energy we can create that will do it, if the reason conservation is being violated is the injection of energy from some other effect or something.