I’ve been thinking aout this for a long time. Is there any technology available today, or maybe in the not too distant future, that would empower us to reduce our solid waste down to its smallest components, then pack them into a container as densely as possible, then shoot them via rocket ship toward the nearest black hole and have them disappear forever?
Is there any possibility that they’d shoot back out of the “back door” of the black hole a vew mintues later?
First of all, sending anything into space is really, really expensive, way more expensive than the cost of any other form of waste disposal.
Second, there’s no reason to break it down to its smallest components: Why bother, if you’re just getting rid of it anyway?
Third, the nearest black holes we know of are all really, really far away, such that it would take many millennia for anything we launched to reach them. You might as well just send things off in some random direction into deep space; the effect would be the same.
Fourth, what could we possibly want to get rid of so thoroughly? Garbage is valuable; we’d be much better off keeping it nearby where we can make use of it if we want.
All that said, though, black holes don’t have “back doors”. If you do somehow manage to send something into one, you’ve gotten rid of it in the most thorough way conceivable.
I would guess the OP means the possibility of a black hole generating a wormhole as the ‘backdoor’…or maybe it’s a sexual reference about black hole backdoors and junk in the trunck…
Let’s suppose we have a spaceship or space station already up there that has some trash. They at least are in Earth orbit - they could be in solar orbit or could even have achieved the escape velocity of the solar system. Could a capsule/pod/cargo ship be dispatched from lunar orbit with a calculated destination of a known black hole with a reasonable chance of actually making it into that black hole, or is it likely to “miss” because we can’t get the numbers quite right or can’t get fine enough control over the heading in real life due to the type of thrusters we have, and the cargo ship ends up orbiting a red giant or something else?
the nearest known black hole is 1600 light years away. Even if you were in interstellar space having achieved solar system escape velocity, your pod is going to take millions of years to get there. By that time the black hole has moved, and no we can’t know where it’s going to be in millions of years accurately enough because the black hole will almost certainly gravitationally interact with other objects (nearby suns etc) in the millions of years it takes for your trash to get there.
It is a bad solution even if it were possible. It would be less bad to just dump all your rubbish on Mars.
Also, it’s not quite what you’re talking about, but there’s a good short story you can find online called “The Clockwork Atom Bomb”.
If it seemed feasible to launch trash toward a black hole, why not just launch trash toward the Sun and let it all become one with the molten plasma there? Turns out, launching trash into space and/or toward the Sun has already been thrashed out right here by the Brain Trust of the SDMB. A quick search yields at least the following four threads:
Launching trash into space - Factual Questions - Straight Dope Message Board by CheeseDonkey 02/07/2011
Expel all the trash to space! - Great Debates - Straight Dope Message Board by jrriojase 11/07/2011
Why can't we just dispose waste out in space? - Factual Questions - Straight Dope Message Board by our very own favorite, Diamonds02 02/28/2010
Would There Be Any Ill Effects to Launching Things Into The Sun? - Factual Questions - Straight Dope Message Board by Alastair Moonsong 04/19/2009
General consensus: It’s too energy-intensive to boost junk up there.
Physicist Tony Rothman suggested using garbage dumped into a nearby black hole as a way to generate energy. I don’t recall the details, but it’s in his novel The World is Round.
The people doing this were living very close to a black hole, so it wasn’t that long a trip. Don’t try this at home.
Presumably, breaking it down to its smallest components would also involve extracting everything valuable from it, leaving only the valueless stuff, for varying values of “valueless”. And incidentally reducing the mass you need to throw out.
But of course even then, it would not be energy-efficient to jettison it into space.
Then we run into the question of whether we can recognize what might be considered valuable in the future. I can imagine our descendants cursing us because we didn’t know enough to not make all the (whatever) we used as (whatever) unrecoverable, simply because we didn’t know how to use it for (whatever).
I wonder if it could ever be cost effective to get rid of nuclear waste by tossing it into space via a space elevator.
I think it might eventually be cost effective to do so – it may be the only thing worth jettisonning in the next century or so. But who knows if we will later find a use for a lot of our current radioactive “waste”.
Never throw away anything. This century’s waste is the next century’s power source. Nuclear waste especially. Why get rid of it at all? Reprocess, compress, then stash the rest in the center of White Sands with a fence around it. Our grandchildren will thank us for our foresight.
A rail gun, pointed toward the sun.
But I think burying that shit deep, deep below the earth’s surface will be adequate enough until we are able to finally employ cleaner energy solutions.
Also, as pointed out, there isn’t much we would want to get rid of so immaculately. Especially at the expense to accelerate it to the adequate escape velocity of the sun; even all the “garbage” in landfills across the globe are but the tiniest specks of dust in relation to the vastness of space itself. Squirting it into a black hole becomes pretty trivial at that point.
If you want something to hit the sun, you don’t point it at the sun: you point it in the opposite direction of the Earth’s revolution, and fire it at the same speed we’re travelling around the sun. Then it’ll simply fall.
There are cheaper (less energy-intensive) paths to the sun, but they’re complicated and constantly changing.
And as a bonus, you will be slightly increasing Earth’s orbit. If we had thousands (millions?) of railguns constantly firing garbage into the sun, we would be able to stave off being fried by the sun in a billion years.
Why can’t we just determine which direction our solar system is orbiting the galactic centre, fire our rubbish behind us, and worry about it 260,000 years later when we are back near where we started?
Would we have enough mass here on earth to actually make any appreciable difference and be left with a planet?
I calculated that we would, if we shot the gun at the maximum speed foreseeable for a rail gun in the medium term future. Unfortunately, I don’t remember if that was faster or slower than the orbital speed of the Earth. And at any rate if we launch enough weight then we will get lighter and easier to push 
…somewhere, thousands of lightyears away, there exists a world. A civilized world, on the brink of oblivion. For thousands of years, this world has been siphoning off just enough mass from their sun to keep it from collapsing into a black hole. That is, until one day, an extraterrestrial chunk of jetsam came hurling in—drifted from another system—and was swallowed by their sun… alas, just enough to tip the scales yet again, sealing their doom…