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Could you lower a wire with recording camera into a black hole and pull it out again?


Neil9327
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Just a thought experiment. If you were in a heavy spacecraft in orbit around a supermassive black hole a comfortable distance outside the event horizon of a black hole then would it be possible to lower a camera on a length of string, recording at the camera, down into the black hole (deeper than the event horizon) and record what it sees, before retreiving it for viewing by pulling it back up with the string.

 

The camera would have rocket motors to make side-to-side adjustments if necessary (to keep the string straight and radial to the orbit).

It would obviously assume a very strong and long piece of string, of low mass.

As it is a supermassive black hole the spagettification effects would be small.

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no, you couldn't. the wire would be held together by electromagnetc interactions between the molecules.

 

even if the tensile strength was for all intents and purposes infinite below the horizon, the photons that mediate the force wil be sucked into the hole before interacting with the other molecules.

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no, you couldn't. the wire would be held together by electromagnetc interactions between the molecules.

 

even if the tensile strength was for all intents and purposes infinite below the horizon, the photons that mediate the force wil be sucked into the hole before interacting with the other molecules.

 

But just below the event horizon of a supermassive black hole the tidal forces are quite small and the gravitational force would be relatively small (but over a large distance from space a high negative potential energy) so at any point in the string surely photons etc would work nearly normally with regard to providing strength. After all they do say that if you are falling into a black hole through the event horizon of a supermassive black hole you would not be obviously aware of it, so the photons are doing their job there.

OK in that scenario you are not accelerating, but for supermassive the value of g is quite modest anyway

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Trying to escape from past the event horizon would take an infinite amount of energy.

 

For this to be the case in my scenario then as work required to pull camera out = integral of force over distance then since distance is finite (it is less than half the orbital diameter of the orbiting mothership) then force would have to be infinite at some point(s) near the event horizon. But as I stated earlier an astronaut falling through would not notice significant tidal forces/spagettification effects until well inside the event horizon (for a supermassive black hole). So this would indicate that the forces are not infinite. So the energy cannot be infinte.

 

Where am I going wrong in my understanding?

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and just Suppose you Could do this with a magic wire, you`de also need an Equally Magic camera too, as the electrons within it would be subject to the effects, as would Photons if you went Reto-tech and used film.

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With all due respect you are not answering my question in terms of a rebuttal of my hypotheses.

There is no "infinite" anything at the event horizon - the only place where anything might be infinite is at the singularity, and that is much in doubt because of quantum mechanics.

 

When you descend into a black hole the only thing that makes it special is that light shone out will not get out. But light once transmitted is effectively in freefall with no sustained propulsion onwards.

What I am proposing is effectively a sustained propulsion out from inside the event horizon outwards until you reach an orbiting mothership.

 

I accept my hypotheses is wrong - What I want to understand is where it is wrong.

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What I am proposing is effectively a sustained propulsion out from inside the event horizon outwards until you reach an orbiting mothership.

 

I accept my hypotheses is wrong - What I want to understand is where it is wrong.

 

Light is massless, and is also the travelling at the fastest possible speed, yet it still is not travelling fast enough to escape the gravitational pull of the BH.

 

You are propoping that an object with mass should be able to accelerate faster than light, fast enough to overcome the pull of gravity, and escape past the event horizon.

 

Since nothing can go faster than the speed of light, and since nothing with mass can even reach the speed of light itself, I believe I've just addressed your request to understand where your hypothesis is wrong.

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Light is massless, and is also the travelling at the fastest possible speed, yet it still is not travelling fast enough to escape the gravitational pull of the BH.

 

You are propoping that an object with mass should be able to accelerate faster than light, fast enough to overcome the pull of gravity, and escape past the event horizon.

 

Since nothing can go faster than the speed of light, and since nothing with mass can even reach the speed of light itself, I believe I've just addressed your request to understand where your hypothesis is wrong.

 

But that would only be the case if I will be giving one big tug on the string to accelerate the camera to greater than light speed, and allowing it to come up to the mothership decelerating all the time to stop at the mothership. No I am not suggesting that. What I am suggesting is a sustained pull on the string to keep the camera moving up out of the black hole at, say, 10 meters per second until it reaches the mother ship. i.e. the kinetic energy of the camera is small.

What force would be required on the string to do this is the question.

 

I suppose I could ask another question to clarify my point: If you just wanted to keep the camera stationary below the event horizon - i.e. hanging the camera from the end of the string, what would be the "weight" of the camera? what force would be exerted on the string? The answer might be "infinite" but if that is the case why does an astronaut not feel any of this infinite force as he falls through the event horizon (assuming supermassive black hole)

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The event horizon of a black hole is the surface inside which the escape velocity is bigger than the speed of light. A photon fired upwards cant get through it.

However, while the escape velocity from the surface of the earth is about 11Km/s (IIRC) it's perfectly possible to build a ladder and climb into space. You don't need to excede the escape velocity to get out provided that you have something to climb.

 

 

The idea that there's no light in a black hole isn't valid. It's perfectly possible that the universe is a black hole and the bit of it I'm in isn't dark.

 

The problems of falling into a black hole don't necessarily start at the event horizon. If the hole is massive enough the graviattional potential gradient near the event horizon might be small enough to not matter.

You wouldn't notice that you had gone through the event horizon.

If that's the case then the point about integrating a finite force over a finite distance is valid. There's no requirement for any infinite energy.

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I suspect the problems arise because measurements are being made in different reference frames, and you are not free to just jump between them in your analyses.

 

 

I can't vouch for the veracity of the site, but I found

http://www.mathpages.com/rr/s7-03/7-03.htm

 

"Thus when we say "the gravitational acceleration goes to infinity as our radial position approaches 2m" we really mean that the amount of acceleration required to boost us into a hovering frame goes to infinity"

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I suspect the problems arise because measurements are being made in different reference frames, and you are not free to just jump between them in your analyses.

 

 

I can't vouch for the veracity of the site, but I found

http://www.mathpages.com/rr/s7-03/7-03.htm

 

"Thus when we say "the gravitational acceleration goes to infinity as our radial position approaches 2m" we really mean that the amount of acceleration required to boost us into a hovering frame goes to infinity"

 

 

Well that looks quite theoretical, but what it seems to be saying is that although the value of g at the event horizon is small that due to relativistic effects and the curved spacetime the actual acceleration tends towards infinity. So that would break the string (in my analogy).

 

I'm happy with that. Relativity is weird.

Thanks for your answers.

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