- #1

Herbascious J

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- TL;DR Summary
- I am wondering if an object can fall into a blackhole at faster that the speed of light. I have heard that the expansion of the universe can make distant galaxies appear to recede faster than the speed of light. Can a black hole also cause geodesics to appear faster than c?

I am wondering if an object can fall into a black hole at faster that the speed of light. I have heard that the expansion of the universe can make distant galaxies appear to recede from one another at velocities faster than the speed of light.

Intuitively, this makes sense to me. I am assuming that according to GR the expansion of space time is a metric expansion of space itself and therefore the galaxies are simply receding due to expansion and not due to local velocities (in a sense it’s as if they are standing still as space grows).

But here is my confusion. If GR allows for the expansion of space to behave like this, is it not also true for any object freely following a geodesic in space-time. Aren’t even orbiting objects kind of ‘standing still’ as well and it’s just the curvature of space-time that makes them appear to gain velocity as they ‘fall’ through a gravitational field.

If GR allows this on the large scale, it seems that if a black hole were massive enough, it might curve space enough to bring objects past light speed as well. I understand that a local velocity is very different from a distant velocity, but I can’t intuitively imagine at what point things change and how. Thank you for any clarification.

Intuitively, this makes sense to me. I am assuming that according to GR the expansion of space time is a metric expansion of space itself and therefore the galaxies are simply receding due to expansion and not due to local velocities (in a sense it’s as if they are standing still as space grows).

But here is my confusion. If GR allows for the expansion of space to behave like this, is it not also true for any object freely following a geodesic in space-time. Aren’t even orbiting objects kind of ‘standing still’ as well and it’s just the curvature of space-time that makes them appear to gain velocity as they ‘fall’ through a gravitational field.

If GR allows this on the large scale, it seems that if a black hole were massive enough, it might curve space enough to bring objects past light speed as well. I understand that a local velocity is very different from a distant velocity, but I can’t intuitively imagine at what point things change and how. Thank you for any clarification.

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