Why can't information be conducted out of a black hole?

Question

• Why can't information be conducted out of a black hole?

• Does gravity affect conduction?

• What is the temperature profile in equilibrium of a metal pole half in, half out of a very large BH such that gravity is low?

• What if the external half is insulated?

• Similarly, what happens to electrical signal conducted into and out of a BH?

• Or signals transmitted from say a camera?

Answer 1

The event horizon is not a physical object, but it is a boundary, where the escape velocity equals the speed of light, and inside the event horizon, the escape velocity exceeds it.

In General Relativity, no amount of force, exerted through a tether or in any other way, can extract an object from the interior of a black hole. There are no “tricks” to get around this fact, any more than there are tricks to make a perpetual motion machine possible. All future-directed timelike worldlines within the interior lead to the singularity, not just ones for freely falling objects. This is a consequence of the black hole’s geometry.

Can an object tethered to a spaceship be pulled out of event horizon?

This means, that no object, nothing, no information can ever be extracted out of a black hole. It should be added that there is no way to keep a long object (like a rod in your example) hovering so to keep one end inside the event horizon at a constant radius, as the effects of gravity will cause the object to break.

If you are interested, there is a specific calculation for the tension on such a rope (or rod in your case).

However, this is misleading without the caveat that for μ < T , the speed of transverse waves in the rope is greater than c, which is not possible for any known form of matter — it would violate the null energy condition. For realistic forms of matter, the rope will break above the horizon.

Another layman blackhole question, pulling one end of a string out from behind the event horizon

The bottom line is that no form of matter can withstand the effects of gravity, and there is no way to exert information out of a black hole.

Answer 2

Have a read about what a black hole is:

A black hole is a region of spacetime where gravity is so strong that nothing—no particles or even electromagnetic radiation such as light—can escape from it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of the region from which no escape is possible is called the event horizon

Italics mine.

The dimensions of the black hole are limited by the event horizon, so there is no way to have anything coming out of the black hole to be able to carry information. Anything that reaches the event horizon, is absorbed with no return, nothing can be half in half out or reflected back from inside the horizon.