Tony Rothman’s SF novel The World is Round has an alien civilization using a black hole as a power source – they dump garbage into it and somehow extract power as it gets accelerated inward (I forget exactly how). Of course, this was civilization that already had a black hole near at hand.
Apparently, if you use the entire mass of the earth, you’d get a black hole about 1cm in diameter.
For the micro BH it may rip micro holes through the material instead of sucking the whole thing in. Sort of like cleaning a window with a pencil eraser sized wipe.
Dropping garbage into underwater subduction zones has been proposed before, The garbage, and for that matter nuke waste would work it’s way into the mantle via seismic activity.
Throwing high-level radioactive waste into the Marianas Trench does have its upsides. Even if the container does fail at some point, the waste itself is heavy enough to remain in place. Water is a great attenuator for radiation. You’d pretty much have to go down there and pick it up with your bare hands to be in any danger from it. Last, and best of all, it will eventually be subducted into the earth’s crust whence it came.
Well, I suppose you could get a small black hole to emit Hawking radiation at the Eddington limit by keeping a continual influx of matter; that’d be a 100% efficient conversion of matter into energy (I reckon that’s how the Romulans did it).
For an efficient garbage compactor, one would have to do a sort of tightrope walk between ‘dangerously heavy’ and ‘dangerously hot’: a 1mm black hole would have a mass of roughly 6.7 * 10[sup]23[/sup] kg (one tenth of the Earth’s mass), and a corresponding Hawking temperature of around 0.2 kelvins; something of a more manageable mass – say, 10[sup]20[/sup] kg --, however, would already be quite hot, around 1200 kelvins. And even that would, from a distance of one meter, still exert a gravitational force of around 680 million g (if I haven’t messed up my numbers anywhere; that seems hard to believe, but it’s what I keep coming up with).
On the upside, it’s more stable than I would’ve thought: its lifetime is on the order of 8 * 10[sup]36[/sup] years. For comparison, a 1kg black hole lasts around 2.5 * 10[sup]-16[/sup] seconds, and has a temperature of a whopping 10[sup]23[/sup] kelvins.
Black holes one could hope to create using the LHC (if there are large extra dimensions) would be around a mass of 2.5 * 10[sup]-23[/sup] kg (assuming it ever gets up to its peak energy of 14 TeV); the ‘classical’ Schwarzschild radius of such a black hole would be around 4 * 10[sup]-50[/sup] meters, however, since we’re dealing with large extra dimensions, it’s somewhat bigger – roughly something on the order of 10[sup]-18[/sup] meters. That’s still about two to three orders of magnitude smaller than the (charge) radius of a proton, so getting anything in there is a challenge.
Another problem would be how to store the suckers – their cross section, assuming there’s essentially no interaction beyond the Schwarzschild radius – a somewhat safe assumption considering the weakness of gravity – would be around 10[sup]-36[/sup] m[sup]2[/sup], or some ten nanobarn. What that means is, basically, that it won’t really interact much with normal matter – trying to set it down on a table would be a bit like trying to set down a brick on a whisp of smoke. So chances are it’s just gonna pass right through your garbage.
So, to sum up, if your black hole’s too massive, you’re gonna have to watch out for gravitational effects; if you make it less massive, it gets too hot; and the black holes we’re capable of making right now won’t do anything much at all (in fact, they’ll be gone in a pop right after they are created).
The point being, basically, I really, really like Wolfram|Alpha.
THERE’S a good OSHA candidate for increased warning signage…
I guess that I was wrong about a 1mm event horizon doing nothing more than perforating the garbage. I’d been under the impression that the only real, inescapable gravity was inside of the black hole, and that you could get right up next to the event horizon without any ill effects.
Just ask Taiwan how well that works. Taiwan is essentially made of the top layers of oceanic crust that got pushed up and deformed instead of actually subducting. When you really look at it in detail, subduction zones are actually extremely messy where the two continents meet. The top layers of oceanic sediment and some of the volcanic layers get scraped off and folded into an accretionary wedge and at that point it’s sort of chance whether it ever gets subducted at all, but in any situation anything on the ocean floor or merely buried in sediment won’t end up in the mantle anytime soon (even geologically speaking).
Another issue with this is that most cements are based on calcium carbonate, which dissolves below the carbonate compensation depth. So entombing them in concrete is definitely a no-no and I don’t know if there exists an economic deep-sea friendly alternative.
The Marianas aren’t the ideal location. There was a proposal to dump spent nuclear fuel at an area in the Pacific ocean at 32N 164W. There is a continuous accumulation of sediment there, so whatever you drop there ends up being buried deeper and deeper over time. The analysis said it was much safer than Yucca Flats.
There was a chapter about it in the book: “Power to Save the World”.
I personally think that Yucca Flats is fine as a temporary storage facility until the United States starts recycling spent fuel again, as we did before President Carter suspended it.
In practice, you’ll only get about 20% efficiency, since most of the Hawking radiation will be in neutrinos, which we can’t harness. It’s probably a better bet to just extract gravitational potential energy from the stuff you’re dropping in: That can be up to 50% efficient, and works for a hole of any size. This, incidentally, is how quasars are powered.
I like the idea of a Large Hadron Garbage Disposal. Also, it would make a good spot for my enemies.
ETA: arg, now I’m thinking of Meet the Spartans…
But a point source smaller than a proton at 1200 kelvins wouldn’t be emitting very much total energy. How big does the black hole have to be before it’s Hawking output is a significant amount of energy? I suspect that to make up for the smallness of the emitting area the temperature would need to be cosmic ray hot.
If it gets bigger, it gets cooler, and the scaling is such that the most power you could get would be from a hole as small as possible.
By the way, I should have mentioned before that using “singularity” as a synonym for “black hole” is something of a pet peeve of mine. There is (presumably) a singularity at the center of a black hole, but it’s safely hidden away behind an event horizon, and there are also other kinds of singularities other than black hole ones. If you mean to say “black hole”, then just say “black hole”: Just because “singularity” sounds more sciency doesn’t mean it’s more technically correct.
Stop right there, or we will have to take off and nuke you from orbit on account of, well you know, being sure and all that.
Ah yes, you’re right of course. Another alternative would be to have a rotating black hole, and extract rotational energy via the Penrose process; I’m not sure about efficiency in that case, though.
Ah, but* will *you take off?
I assure you, given the gravitational forces involved, the last thing you want to do with a tiny black hole is stick your penis in it. ‘Cause once it passes the event horizon, it ain’t comin’ back out again.
Yet another addition to the list of “things not to stick it into”
P–e—n----i-----s --------------- e-------n---------s---------u----------e-------------------------------------------------------------------------------------
Golf clap. Well played, sir.