# Two spaceships fly straight, parallel to each other, tied to each other by a rope, and pass a black hole between them. What happens to the rope? [closed]

To elaborate more on what I mean:

Two spaceships are flying parallel to each other, both going completely straight relative to the observer. Their distances between each other do not change, as the rope is completely straight, and it does not move closer or farther as they are going parallel. While flying together, they pass a black hole, which is perfectly between them, and they are both equidistant from the black hole. Not accounting for the gravitational pull of the black hole on the spaceship, what would happen to the rope?

I guess you could take the entire spaceship idea out of the equation. To simplify, what would happen to a rope, of which both ends are past the event horizon, and do not move? In other words, relative to the observer, the middle-point of the rope appears to be moving directly in to the center of the black hole. Asking this in a non-pragmatic sense, what would happen?

• My feeling is that questions about physics that take place in space incidentally are off-topic in Space Exploration SE. We can't add "... in space?" or "imagine two space ships flying with a rope, now forge the space ships and only address the rope." to a question to make it on-topic.
– uhoh
Commented Nov 9, 2020 at 7:49
• a potential use of rope in space: What was Apollo “Moon rope” made out of? Was it ever used?
– uhoh
Commented Nov 9, 2020 at 7:52
• I think that Astronomy SE or Physics SE are possible alternate sites for this question, but I am not sure.
– uhoh
Commented Nov 9, 2020 at 7:56
• I’m voting to close this question because I think it clearly belongs in Physics SE. However it's worth pointing out that the situation with the two spaceships is complicated because from the perspective of the spaceships the rope never passes the event horizon, unless they do.
– user21103
Commented Nov 9, 2020 at 11:03

The engineers answer: the rope will break.

The physicist answer: the rope will pull the two spaceships inside the black hole.

So you are asking in a "non-pragmatic" way: the physicist answer...

Why?

E: Coming near a black hole, the gravitational forces of the black hole will pull more and more jet not equal through the whole lenght. The shear forces will brake the rope.

P: Once inside the event horizont of a black hole nothing can leave, no single atom of the rope, but instead it will pull the rope. More and more rope will be pulled till everything connected is inside.

• The enthusiast's answer: the rope will cut the black hole into two parts. These parts will swirl each other and eventually merge into one with formation of gravitational waves. Gravitational waves will be detected by the LIGO laboratory. The scientific community will be enlighted with this discovery. The rope and spaceships will be just fine. Commented Nov 9, 2020 at 13:02
• Your “physicist’s answer” contradicts the problem statement. Commented Nov 9, 2020 at 15:48
• No, it was posted before the edits of the original question Commented Nov 9, 2020 at 17:13

If the ends of the rope are constrained to move along straight lines past the black hole, the rope breaks.

The effect of gravity of a massive body varies inversely with the square of distance from the object’s center of mass. For small objects near ordinary massive bodies this gravitational gradient is small, but near a black hole the gradient gets very significant, and any single bit of rope is subjected to significantly different forces than its neighbors. At some point, the rope gets close enough to the black hole that the difference in force exceeds the tensile strength of the rope.