Brain Teasers
Two Black Holes
Science
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Aliens are placing you near one of two black holes in outer space. They give you a choice of being placed near a large black hole or a small black hole. Keeping in mind that when you go close to a black hole you must worry about large gravitational tidal forces produced by a black hole, which do you prefer, if you wish to escape?
Answer
The large black hole. Tidal forces (near the event horizon) are smaller for large black holes than for small holes, because more massive black holes actually have a lower density, and the exterior spacetime is less curved. If you were approaching a 10-solar-masses black hole with a radius of 30 kilometers, you would be killed long before you reached the horizon at an altitude of 400 kilometers. However, you could reach the horizon of a 1,000-solar-masses black hole. The tidal forces at the horizon of this gigantic black hole would be weaker than those produced by Earth, which are already impossible for us to feel. Of course, once you crossed the horizon, you would eventually be pulled into the singularity and then be torn to pieces by the finite tidal forces. This final fate awaits you no matter what the mass of the black hole.Hide Answer Show Answer
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Comments
so, either way you are dead, so it doesn't matter. But incase you are a superhuman with faster than light speed and can fly and have all the divine forces one your side, you should take the big one.
no exactly, it said that it would take you near one of the black holes, not that they would put you in it.
well ya but you'd have no way of getting away and the gravity would eventually pull you in.
you are absolutely right i have always found the this stuff fascinating.
But how would you breath?....wouldn't you be dead before you even got anywhere near these black holes from lack of Oxygen????
"small" black hole might be taken to mean "primordial" black hole as proposed by Stephen Hawking, in which case I would prefer being next to the small one, and preferably one that has been drained to near evaporation.
you do of course realize that a black hole, is just that. So dense that not even light escapes from it, while the density might not be as great, it is still great enough to not allow light to escape it. Thus having a much larger event horizon. And of course you do realize that in either case if you were to cross the even horizon you would never reach the center because of the affect of gravity on time. the entire universe would end before you reached the center.
Hmm....the small black hole would be more likely to sling you out before you hit the point of no return...you could call that the seduction of the large black hole...anyway, will the aliens pick me up if i survive outerspace and am slingshot away from the hole?
I already knew to go for the larger one, but for some reason the only word that formed in my mind after your description of what would eventually happen to me was "Charming. "
If placed 'near' it would mean not past event horizon otherwise you would be in it. If the idea of escape is even there, I would want the small one so there would be less distance to travel to go around the event horizon. Also if I did not have sensors to even detect the hole, the small one offers less chance of entering accidentally. Blindfolded...avoid the puddle vs avoiding the pool.
It wouldn't matter which black hole that you chose. If you were to fall in you would be spaghettified either way. All that would change is what side of the event horison that you are on when you meet your end. If you were to some how aquire a rocket ship to escape before you reached the event horison, the acceleration needed to acheive escape velocity would crush you flat as a pancake anyway. That is, depending on how "near" to the either black hole that you were. Lastly, a black hole's volume is dependent upon the mass of it's singularity, which is infinitely dense (or some semblance there of). Wouldn't that prove that all black holes have the similar if not the same density, regardless of size?
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