How would a miniature black hole behave on Earth? What would it look like? How quickly would it suck in its surroundings? Could it be transported? Does it need to be contained? If not, would it make a beeline for the center of the planet? :eek:
If given in a electric charge, presumably by bombarding it with electrons, could it be contained in an magnetic bottle?
What would actually happen if a really small black hole - the size of atomic nucleus say - encountered ordinary matter. Would the comparitively weak gravitational force overcome the much stronger electromagnetic forces that hold nomal matter together?
Don’t small black holes evaporate really quickly anyway?
Yup – at a rate inversely proportional to the mass. Mini-black holes would have an exceedingly small lifetime and would vanish in a burst of high-energy particles. you wouldn’t want to be around.
a science fiction story depicting mini-black holes, written before Hawking decided that black holes “evaporate”, is Larry Niven’s “The Hole Man”. For a picture of how ultradense matter doesn’t behave, read Fredric Brown’s rogue in Space. Brown was a helluva writer, but his knowledge of physics was minimal – the neutron matter he describes would tear the hero apart by tidal forces, if it didn’t sink to the center of the planet first.
Make that inverse square of the mass, for the rate, making the lifespan proportional to the cube of the mass.
And CalMeacham proably meant to also say that Niven’s story is an accurate description of how such a hole would behave, other than the whole pesky Hawking radiation business.
If you do give the black hole a significant charge, then you can indeed manipulate it using electromagnetic methods. More likely than trying to hold it in a magnetic bottle would be to just use a (mostly) static electric field to support it against the Earth’s gravity (I say mostly because a truly static electric field would be unstable, so you’d need to adjust the field a bit to keep it balanced). Exactly how hard this would be would depend on the size of the hole. We can’t make black holes smaller than a mid-sized star, so any smaller than that would have to be found as a relic of the Big Bang, and there’s very little known about the expected sizes of those, so you can pretty much postulate such a black hole being any size you like.
Not “probably mean to say”, but did:
I’m pretty sure we can’t make black holes larger than a mid-sized star either. At least not here on earth. 
How would a mini black hole “evaporate”? I thought that the whole idea was that nothing could escape from within the event horizon.
As I understand it, spacetime is a sea of virtual particles. Thanks to the uncertainty principle, they appear ( in matter/antimatter pairs ), then mutually annihilate and vanish.
However, if they appear at a black holes event horizon, one of the pair can be sucked in and the other escape. It then becomes a real particle with real mass-energy which needs to come from somewhere, namely the hole. The process is more efficient for smaller holes, so they evaporate faster and faster until they vanish in a huge blaze of radiation.
What really can’t escape is information. Hawking radiation is purely random; no data on what the hole ate ever escapes.
The theory (prior to Hawking’s “evaporation” theory) was that there could be “quantum black holes” left over from events at the formation of the universe that were formed by compression of matter by external forces, rather than by gravitational collapse.
Far better than either Niven’s or Brown’s is David Brin’s Earth, which includes correct information regarding black holes as of 1989. Unless you already know quite a bit about quantum physics, it will give you some painless education on the subject.
Brin is a physics Ph.D. - it also has some interesting hypotheses and good story lines (several major characters); if it didn’t, it wouldn’t be good SF.
Painless? I don’t know about that. This book will hurt you. And not in a good way. Way too much technobabble (correct or not) and the slowest pacing I’ve seen in a long time. I was hoping the black hole would win, consume the earth and take Brin with it.
For the layman’s answer to the above, you need look no further than the standard washer/dryer. These all seem to be equipped with a black hole that regularly eats my socks.