You stick your hand in a black hole. What happens?

Question

A professor when I was in grad school once asked this question. Say you're in a spaceship in orbit near the horizon of supermassive black hole --- i.e. one which is large enough that tidal effects are negligible for you. (And say it's nonspinning.) You try to put your (spacesuit-shielded) fist in hole. What happens?

I suspect the best answer may be "you get bored, pull your hand back and go home because it seems to be taking forever for your hand to move inwards as far as your brain is concerned". But I'd like to see your comments! (Not for homework: just curious!)

Answer 1

Consider the graph of effective potential (i.e. that including the angular momentum contribution) vs. radius 'r' for a test particle in orbit around a Schwarzschild hole. i.e. for timelike geodesics. The slope of this graph at any value of r can be regarded as the force required to keep an object in orbit at that radius. At r=3M, the slope can be zero (if the angular momentum's right), but for smaller r (i.e. approaching the Schwarzschild radius r=2M from larger values of r), this slope increases rather sharply (as r->0 the r^-3 term dominates). Now, this is still FINITE, not infinite at r=2M (so the thread posted by the Canadian guy has incorrect info) but it can still be very large... So, to keep your arm intact, you'd have to keep your whole arm more or less in orbit at a succession of raidi approaching r=2M.

This then becomes a medical question: how strong is your arm? If it's not strong enough, your hand breaks off (or something) and the lost bits freely fall into the hole. If your arm is "strong enough", however... hmmm. That's a good question!

...Oh, and tell your ship's captain: "Don't forget to compensate for the decay of our orbit due to the gravitational radiation we're emitting!"

Answer 2

I do not believe in the event horizon for many reasons some similar to your question. I think it is just a mistake was made in the mathematics. This is what classical theory gives.

First of all there is no stable orbit that close to an event horizon, not even at the speed of light, so you would have to burn massive amount fuel each seconds just to maintain your position. I do not think you can even carry enough anti-matter to do the job.

Second there are no street signs saying event horizon 2 feet away.

Third classically the event horizon is the point of no return you will not bring your hand back. More than likely you would follow, if the black hole is big enough that tidal forces don't tear you apart your arm would still weight millions of pounds or even trillions (remember I said there is not stable orbit)

Answer 3

actually, no, they does no longer be of the Planck Mass. merely to, "humor" you, how ought to they? How can subatomic debris earnings a lot mass that they might weight about a million/4000th of the burden of the flea? What would ensue in case you stuck your finger right into a tiny black hollow will be that you finger be sucked in, slowly yet actually. The gravitational power will be too small to do some thing, yet perchance some atoms would fall in. to grant you an theory: The Planck Mass is the minimum mass for a black hollow to have a radius equivalent to its Compton wavelength, and would have a life-time equivalent to the Planck Time (it really is 10^-43seconds). The black holes produced in the LHC will be risky, yet they might exist for a finite (inspite of the actual undeniable truth that a non-recordable quantity) era of time. Why? because a particle that has a non-0 mass, the speedier it is going, the mass will improve. Its a similar concept that dictates that one can not bypass at or speedier than the speed of sunshine. because a photon is massless, it may. A neutrino, which travels at just about the speed of sunshine, has a non-0 mass. So yeah, its no longer going to ensue. The smallest reliable black hollow that ought to have a existence of about the age of the universe, you would could compact Mount Everest, into an quite, quite, quite small area. to positioned it in percentage: If Earth replaced into to illustrate right into a black hollow, it will be about the scale of a marble.

Answer 4

A black hole and a sun would both be a node phenomena--as is time!A black hole is a sun in the past.I would say that your hand would disappear unless you stuck your head in there also.

Answer 5

Well, before you even got close to the black hole, you'de be ripped apart by the gravitational forces. In essence, you'de never even get close enough to stick your hand in. You'de already be dead and in a thousand pieces.

Answer 6

If you put your hand through a blackhole, you can't get it back. It's not because of another dimension, which is a theory, BUT your hand will burn even if you have something trying to protect your hand. Blackholes produce heat since u can see heat with certain instruments. So your hand will burn or collapse with teh gravity.

Answer 7

What kind of confusion promotes such an absurd question?

A "black hole" is not a hole.

Answer 8

black holes don't only suck ur fist but urself.. everything vanishes in black hole. its a super duper gravitational field zone where even planets dissappear.

Answer 9

It depends on what is on the other side of that hole, if anything.

Answer 10

Oh sorry. I thought you were talking about black chicks.