November Entry - Real Science

[Immolate]

So in effect you're saying that a black hole of the most most basic sort--one that was just born and as small as one could be--could not accrete sufficient matter while remaining in a single spot to make up for the energy it was shedding and therefore would burn itself out? That I did not know, nor did I know that it takes a lot of time for them to eat enough to begin exerting pull at any distance.

What I'm hearing is that a black hole needs to be fed in order to survive, and therefore stability would require a steady source of intake relative to the output, which my disaster / eighth wonder of the world / theme park scenario does not allow. Although the nuclear, biological and chemical trash collectors across the world now have a bottomless garbage pit, not to mention all of the conventional waste disposal companies in a large radius, it would not be enough or really regular enough to allow stabilization.

So if I didn't completely misunderstand what you said, Brin's fiction of a singularity sub-orbiting the planet could only cause planetary destruction by slowly gobbling up all of the liquid rock as it zips around, eventually causing the crust to begin to collapse, bit by bit. I'm not saying this would be devastating and probably quite fatal to life on earth... just not quite the dramatic and sudden end envisioned in the book.

I guess the reason Brin had the singularity orbiting is that he learned enough about the science to know the little guy had to move to survive.

[edit] I was ready to move the offending experiment from Atlas to CMS because I couldn't bear the thought of destroying the PSP, but from what you're saying, the singularity wouldn't really do any detectable damage on its way to the center point of the collider because it would still be tres tiny... correct? If that is the case, I can leave it as it is (in my head) and just stick with the fiction of growing the black hole faster and bigger than it could actually grow. Also, only the slowest scientists would be unable to evacuate the Pressin site before the singularity grew large enough to get to them (a period of months in my alternate unreality).

[torstan]

If a black hole is created then it'll have the mass of whatever produced it. So if we create one from proton collisions then the most mass it's going to have is equal to the energy of the collision - so 7TeV on the current version. Actually we'd expect that only a small fraction of the energy would be caught in a black hole. Now that's the equivalent to the mass of only 7000 protons. When you're relying on gravitation to pull in new matter for it to grow, 7000 protons is really a very small mass.

This is to be compared to the mass of a star which is what astrophysical black holes are created from. Now their gravitational force is truly fierce because they contain the mass of the star that formed them. If one of those was orbiting the earth, then it would tear the planet to shreds.

Now the complication is that Hawking radiation says that black holes emit energy and lose mass. For a big black hole this energy loss is negligible compared to the speed at which it accretes new matter. However for a small black hole the energy loss is greater than the mass it gains by sucking in new matter and the black hole would evaporate. However as we haven't seen Hawking radiation people have argued that black holes might not evaporate and might instead grow larger and gobble up the world.

Even if the black holes don't evaporate through Hawking radiation, they would gain mass extremely slowly, and wouldn't pose any threat to the earth until well after the sun had exploded.

So you could say that the black hole is created and travels to the center of the ring. As long as you say that Hawking radiation doesn't exist, the black hole will be stable. It will slowly eat up all the matter around it, until it's sitting in a hole. The stuff around the edge of the hole will be too far away to be pulled in so the black hole would just sit there, slowly eating up any passing air molecule that gets too close. Obviously if you throw more garbage in there then it will grow. But you need to throw a lot of stuff in there for it to get big. And by a lot we're talking continents and suchlike.

So you need to say there's no Hawking radiation, that it stays in the middle of the ring and that for some reason it's gravitational pull is much larger than we'd expect (perhaps some weird quantum gravity effect, extra dimensions or something like that) so that it sucks in matter from further away than we'd expect. With those three things you'd get yourself your disaster.

On a side note, people are very serious about looking for black holes at the LHC. If we saw one it would be very cool indeed and would revolutionise particle physics. It would not pose any threat to anything.