I have known for a very long time that light cannot exit a black hole. I can even understand some of the simpler reasonning about it, such as escape velocity, or space geometry inside the black hole.

But I have a consistency problem. I learned in school (very long ago) that the path followed by light is independent of its orientation on this path. This seems confirmed by the fact that light follows geodesics. Possibly I misunderstand what that means or imply.

It the path is independent of travel orientation, any path in is necessarily a path out. Thus, if no light can escape a black hole, I would expect that no light can enter it.

Yet, I often read that it does (though we cannot see it happen).

So, what do I misunderstand?

I have also some problem reconciling that with some descriptions of the event horizon as a rather quiet place when its radius is very large. But that is just a side remark.

Possibly related question: What is the reasoning behind the idea that light cannot escape from a black hole?

• What is the reasoning behind the idea that light cannot escape from a black hole?

• Why can't light escape from a classical black hole?

• Why is a black hole black?

I have known for a very long time that light cannot exit a black hole. I can even understand some of the simpler reasonning about it, such as escape velocity, or space geometry inside the black hole.

But I have a consistency problem. I learned in school (very long ago) that the path followed by light is independent of its orientation on this path. This seems confirmed by the fact that light follows geodesics. Possibly I misunderstand what that means or imply.

It the path is independent of travel orientation, any path in is necessarily a path out. Thus, if no light can escape a black hole, I would expect that no light can enter it.

Yet, I often read that it does (though we cannot see it happen).

So, what do I misunderstand?

I have also some problem reconciling that with some descriptions of the event horizon as a rather quiet place when its radius is very large. But that is just a side remark.

Possibly related question: What is the reasoning behind the idea that light cannot escape from a black hole?

• What is the reasoning behind the idea that light cannot escape from a black hole?

• Why can't light escape from a classical black hole?

• Why is a black hole black?

I have known for a very long time that light cannot exit a black hole. I can even understand some of the simpler reasonning about it, such as escape velocity, or space geometry inside the black hole.

But I have a consistency problem. I learned in school (very long ago) that the path followed by light is independent of its orientation on this path. This seems confirmed by the fact that light follows geodesics. Possibly I misunderstand what that means or imply.

It the path is independent of travel orientation, any path in is necessarily a path out. Thus, if no light can escape a black hole, I would expect that no light can enter it.

Yet, I often read that it does (though we cannot see it happen).

So, what do I misunderstand?

I have also some problem reconciling that with some descriptions of the event horizon as a rather quiet place when its radius is very large. But that is just a side remark.

Possibly related question: What is the reasoning behind the idea that light cannot escape from a black hole?

• What is the reasoning behind the idea that light cannot escape from a black hole?

• Why can't light escape from a classical black hole?

• Why is a black hole black?

I have known for a very long time that light cannot exit a black hole. I can even understand some of the simpler reasonning about it, such as escape velocity, or space geometry inside the black hole.

But I have a consistency problem. I learned in school (very long ago) that the path followed by light is independent of its orientation on this path. This seems confirmed by the fact that light follows geodesics. Possibly I misunderstand what that means or imply.

It the path is independent of travel orientation, any path in is necessarily a path out. Thus, if no light can escape a black hole, I would expect that no light can enter it.

Yet, I often read that it does (though we cannot see it happen).

So, what do I misunderstand?

I have also some problem reconciling that with some descriptions of the event horizon as a rather quiet place when its radius is very large. But that is just a side remark.

Possibly related question: What is the reasoning behind the idea that light cannot escape from a black hole?

• What is the reasoning behind the idea that light cannot escape from a black hole?

• Why can't light escape from a classical black hole?

• Why is a black hole black?