Can Earth Orbit a Black Hole Indefinitely?

[CentricStorm]

If most of the universe falls into a massive black hole, will it be possible for the Earth to be kept away from it, for example by going into orbit of the black hole?

In this situation, the Earth would be the last remaining matter outside of the black hole as everything else in the entire universe has fallen into the black hole, so would we be able to orbit it from a huge distance and never fall in, or would its gravitational pull be so strong that the end is inevitable no matter how far away from it we are?

I am of course assuming that this occurs in an imaginary future scenario in which humans live forever and can live self-sufficiently without needing any energy coming from outside of the Earth like light from a star.

 

[Nabeshin]

If most of the universe falls into a massive black hole, will it be possible for the Earth to be kept away from it, for example by going into orbit of the black hole?

Quick answer: Yes. One can orbit a black hole and remain there indefinitely (the situation is no different from orbiting any other body!)

In this situation, the Earth would be the last remaining matter outside of the black hole as everything else in the entire universe has fallen into the black hole, so would we be able to orbit it from a huge distance and never fall in, or would its gravitational pull be so strong that the end is inevitable no matter how far away from it we are?

Long answer: You eventually fall in no matter what. There are two things to consider here. One is that pertubations by other infalling objects would inevitably either eject the Earth from the black hole system or cause it to plunge in. You can suppose, though, that we have strong rocket jets on the Earth to compensate for these pertubations though, and so perhaps the Earth can make it through the stage where everything else has fallen in. Fine. But now you have a system which is emitting gravitational radiation. Granted, the amount of radiation is so negligibly small (for large distances), that normally we would never even consider it. But over the stretch of countless eons, the orbit would spiral inwards faster and faster until it is finally consumed. Note: This has nothing to do with the fact that the object is a black hole! It's not the strength of the hole's gravity that produces this effect, merely the property that it has gravity. So, to take an example, the system with a tennis ball and the Earth in orbit around each other will produce the same consequence! i.e after a long (very very) time, the orbit will decay through emission gravitational radiation.

I am of course assuming that this occurs in an imaginary future scenario in which humans live forever and can live self-sufficiently without needing any energy coming from outside of the Earth like light from a star.

And of course this assumption is nonsense anyways, since one always requires an energy source. The point is, on the longest of timescales *no* orbit is stable.

 

[CentricStorm]

Quick answer: Yes. One can orbit a black hole and remain there indefinitely (the situation is no different from orbiting any other body!)



Long answer: You eventually fall in no matter what. There are two things to consider here. One is that pertubations by other infalling objects would inevitably either eject the Earth from the black hole system or cause it to plunge in. You can suppose, though, that we have strong rocket jets on the Earth to compensate for these pertubations though, and so perhaps the Earth can make it through the stage where everything else has fallen in. Fine. But now you have a system which is emitting gravitational radiation. Granted, the amount of radiation is so negligibly small (for large distances), that normally we would never even consider it. But over the stretch of countless eons, the orbit would spiral inwards faster and faster until it is finally consumed. Note: This has nothing to do with the fact that the object is a black hole! It's not the strength of the hole's gravity that produces this effect, merely the property that it has gravity. So, to take an example, the system with a tennis ball and the Earth in orbit around each other will produce the same consequence! i.e after a long (very very) time, the orbit will decay through emission gravitational radiation.


And of course this assumption is nonsense anyways, since one always requires an energy source. The point is, on the longest of timescales *no* orbit is stable.

Thanks for the answer.

I guess this means that there is no real way for humans to live forever no matter how far technology advances.