Re: Will any man-made object withstand the forces gernerated by a black hole?

Hi Jessica,

Yes, man-made objects could survive near a black hole, but it depends on how massive the black hole is, and how close you want to get.

There are two ways that I can think of for a man-made object to be destroyed. Black holes which are "accreting" material from nearby stars or interstellar gas will be surrounded by a disk or sphere of this infalling material. The material being accreted is going quite fast as it orbits the black hole, and it heats up (due to friction) and emits X-rays. Encountering this material could damage our "black hole probe", both by colliding with it, and by radiation. The properties of these "accretion flows" are something that theoretical astrophysicists are still trying to work out, so I'm not sure how deadly they would be for our probe.

So let's consider the a non-accreting black hole. It can still damage the black hole probe with its own gravity. The problem for the probe is that the gravitational force of the black hole is slightly larger for the part of the probe nearest to the black hole than it is for the part of the probe furthest from the black hole. This effect produces something called "tidal forces" (it's the same effect that causes tides on the Earth) which, if strong enough, can pull an object apart. These forces get stronger the closer the probe gets to the black hole, so if the probe stays far enough away from the center of the black hole it will be safe.

How far away is "far enough"? It depends on the mass of the black hole. The mass of the black hole also determines the size of the "event horizon" (the "point of no return" beyond which the probe, and any signals it sends, can't escape), and it turns out bigger black holes are better, at least as far as probe survival goes. Ted Bunn's black hole FAQ notes that for large black holes, tidal forces are significant only well inside the event horizon, so a probe could in theory send signals right up to the point where it disappears (which, from the outside, appears to take forever; see the next item in the FAQ.

There are lots more questions and answers about black holes in the MAdSci archive; try our search engine to find them.

Pauline