7 ms·
There's a difference between hovering above an event horizon and sticking your leg through versus free-falling through an event horizon. The former is not an i
by splat 13y ago
There's a difference between hovering above an event horizon and sticking your leg through versus free-falling through an event horizon. The former is not an inertial reference frame, so you would feel enormous forces due to the fact that you were (somehow) generating enough thrust to counteract the gravitational force of the black hole. No human could survive that. But in the latter you feel no forces except for tidal forces because you are simply following the curvature of the local spacetime. If you were falling into a supermassive black hole you would not feel anything as you passed through the event horizon. You would still retain full control over your limbs until a few milliseconds (I think, I might be a few orders of magnitude off) before you hit the singularity.
- tehwalrus 13y agoOK, orbiting rather than hovering. Also, whatever speed you cross the horizon there would still be some delta_t > h_bar where leg atom A can't see leg atom B. Similarly, the drop in blood pressure for the parts of blood vessels just outside the horizon (although, given the rest of the prediction, blood pressure is the least of your worries at this point.)
- Sir_Cmpwn 13y agoThe problem is that you don't understand how an event horizon works. It's not a definite border where suddenly there's a lot more gravity. It's the point at which gravity becomes strong enough (note that gravitational forces are still very strong right next to the event horizon) that not even light could avoid being pulled into the singularity eventually. You wouldn't have to travel directly into the signularity, if that helps clarify things. You could orbit around it for a while and your orbit would decay in a spiral pattern. This excerpt from Wikipedia might be helpful: https://mediacru.sh/rd-9YJEtJRGo https://mediacru.sh/rd-9YJEtJRGo I would expect that you'd be torn apart by tidal forces before you reached the event horizon anyway.
- splat 13y agoYou would be torn apart by tidal forces before reaching the event horizon of a stellar mass black hole, but you wouldn't be torn apart by tidal forces before reaching the event horizon of a supermassive black hole.
- splat 13y agoYou cannot orbit a black hole immediately outside the event horizon. The smallest distance at which a circular orbit is possible is called the photon sphere because you must be moving at the speed of light to maintain a circular orbit. The photon sphere is at 1.5 Schwarzschild radii.
- tehwalrus 13y agoAh, apologies, so this would be impossible with a living thing. If we substitute for a machine? Could you, perhaps, build a strong enough spaceship to dip in close enough to dangle something passed the horizon, and then accelerate away again? I don't suppose you'd be able to measure anything from the resulting object, even if you could get it back... Even if you couldn't, I still find it implausible that even large objects would travel across the even horizon effectively instantaneously.
- splat 13y agoIf you dangle something into the event horizon it will be lost forever. Large objects in free fall wouldn't travel across the event horizon instantaneously. It's just that by the time a signal from the front of the object reached the back, the back of the object would have already crossed the event horizon.
- tehwalrus 13y agoYou forgot that the object is supposed to be attached to very powerful rockets, so not in free-fall, and presumably made of some advanced material that can withstand the acceleration forces. Additionally, you still haven't addressed the issue of atoms, covalently bonded, either side of the horizon (and not in free fall downwards, but being pulled from a rocket above so as to be slower than that.)
- nikbackm 13y agoUnless the rockets can match or exceed the speed of light, does it matter since only photons can maintain a circular orbit that close the event horizon as was already stated? (PS: I think that advanced material you're referring to is also known as Unobtainium :)