Thread: Orbiting a Black Hole

Hey! Could a spaceship [assume its a futuristic one with more advanced technology, etc.] orbit a black hole in order to allow time in the universe to pass quicker than for time in the spaceship? How much faster would time be 'outside' than near the black hole-- and how close would you have to be? Could you tread the event horizon, or would significant time dilation only occur inside the black hole itself- rendering the whole question useless? I'm writing a book and need a method of allowing thousands, tens of thousands of years, etc. to pass quickly for only a few generations of humans. Thanks!

See the book Tau Zero by Poul Anderson.

You can orbit a black hole as long as the radius of your orbit is greater than 3/2 the radius of the event horizon.

The time dilation can be found by



This includes both the time dilation due to gravitational potential and that due to orbital speed.

Originally Posted by MrPiano

Hey! Could a spaceship [assume its a futuristic one with more advanced technology, etc.] orbit a black hole in order to allow time in the universe to pass quicker than for time in the spaceship? How much faster would time be 'outside' than near the black hole-- and how close would you have to be? Could you tread the event horizon, or would significant time dilation only occur inside the black hole itself- rendering the whole question useless? I'm writing a book and need a method of allowing thousands, tens of thousands of years, etc. to pass quickly for only a few generations of humans. Thanks!

Suppose we assume you can do it. Why would you want to do it? It looks like it would be a one way trip into some unknown future. You wouldn't be able to go back in time, so you would be stuck in whatever future you found. What would you do if you found humans went extinct and you and your companions were now the only humans left alive in the galaxy?

~ The concept exists.. and has some 'Issues' Not only would you need to have some special advanced ship

you would need to get there. and knowing the human lifespan and the distances.. 'NO'.

Good science fiction needs to be within probability but that's only 'My' view. Interesting as it is...

Originally Posted by Bad Robot

Originally Posted by MrPiano

Hey! Could a spaceship [assume its a futuristic one with more advanced technology, etc.] orbit a black hole in order to allow time in the universe to pass quicker than for time in the spaceship? How much faster would time be 'outside' than near the black hole-- and how close would you have to be? Could you tread the event horizon, or would significant time dilation only occur inside the black hole itself- rendering the whole question useless? I'm writing a book and need a method of allowing thousands, tens of thousands of years, etc. to pass quickly for only a few generations of humans. Thanks!

Suppose we assume you can do it. Why would you want to do it? It looks like it would be a one way trip into some unknown future. You wouldn't be able to go back in time, so you would be stuck in whatever future you found. What would you do if you found humans went extinct and you and your companions were now the only humans left alive in the galaxy?

That's kind of the point, I'm writing a fiction novel and need a forward time travel mechanism for the plot. thanks for all the help!

Originally Posted by MrPiano

That's kind of the point, I'm writing a fiction novel and need a forward time travel mechanism for the plot. thanks for all the help!

Have them move at near "c" and then return to Earth.

Originally Posted by Neverfly

Originally Posted by MrPiano

That's kind of the point, I'm writing a fiction novel and need a forward time travel mechanism for the plot. thanks for all the help!

Have them move at near "c" and then return to Earth.

Joe Haldeman's Forever War has a relativistic shuttle, that just goes out and back at relativistic speeds.