# Inside a Black Hole: Rest Frame & Singularity

• B
• tionis
In summary, crossing the event horizon of a black hole does not change your state of motion, and the singularity is always in your future regardless of your frame of reference. However, the singularity should not be thought of as a location in space but rather a moment in time, and the properties assigned to it are actually properties of the spacetime geometry.
tionis
Gold Member
Once I cross the event horizon of a BH, is it valid to say that I'm at rest and the singularity comes up to meet me?

The fact of having crossed the event horizon makes no difference other than that from there you can only go deeper into the black hole.
At some time in the fairly near future you will inevitably encounter whatever the singularity is.
You can consider your self to be moving (which makes sense because you considered yourself to be moving before you got to the horizon.),
or you can consider that center of the black hole is moving towards you, which is equally valid.
However there is no good reason why crossing the horizon implies a need to switch to a different frame of reference.

tionis
tionis said:
Once I cross the event horizon of a BH, is it valid to say that I'm at rest and the singularity comes up to meet me?
No.
If you are in freefall, then it is always valid to consider yourself at rest and this works both inside and outside the horizon. However, once inside the horizon there is no way of thinking about the singularity approaching you, or looking towards it or away from it, or being a greater or lesser distance from it. The singularity is in your future, the same way that on Sunday night Monday morning is in your future.

tionis, PeterDonis and Dale
tionis said:
Once I cross the event horizon of a BH, is it valid to say that I'm at rest and the singularity comes up to meet me?
The singularity is a moment in time, not a location in space. It would be a little strange to say "Friday comes up to meet me".

Edit: what Nugatory said

tionis
It is a moment in time, true, but we assign this moment in time shapes, like a ring, and spaghettification powers etc. I still don't understand how a moment in time can have all those attributes.

tionis said:
we assign this moment in time shapes, like a ring, and spaghettification powers etc.

Those properties aren't assigned to a moment in time. They are assigned to the spacetime geometry. (Actually, in Kerr spacetime, the ring singularity is timelike, not spacelike, so it isn't a moment of time anyway, it can be seen as a ring in space. But the ring by itself still doesn't have all the properties you are talking about; they are still properties of the spacetime geometry.)

tionis

## What is a black hole?

A black hole is a region of space where the gravitational pull is so strong that nothing, including light, can escape from it. This happens when a massive star collapses under its own weight.

## What is the rest frame of a black hole?

The rest frame of a black hole is a reference frame in which the black hole appears to be stationary. It is a theoretical concept that allows us to study the properties of a black hole without being affected by its extreme gravitational pull.

## What is the singularity of a black hole?

The singularity of a black hole is a point of infinite density and zero volume at the center of a black hole. It is where the laws of physics, as we know them, break down and we cannot predict what happens.

## What happens to time inside a black hole?

Time inside a black hole is affected by its extreme gravity. As you get closer to the singularity, time slows down significantly. At the event horizon, time stops completely. This means that for an outside observer, it would appear that anything falling into a black hole freezes in time at the event horizon.

## Can anything escape from a black hole?

According to our current understanding of physics, nothing can escape from a black hole once it has passed the event horizon. This includes matter, light, and even information. However, there are some theories that suggest that information may be able to escape in the form of Hawking radiation.

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