[dustingetz]

No, this depends on your choice of coordinate system - has been debunked N times on physics reddit in virtually every thread that it comes up. The EH itself is not a singularity in the observers reference frame as they cross it nor do they particularly notice when they do.

[machina_ex_deus]

I never said EH is a singularity. I said you could notice you're inside as your timelike coordinate becomes the radial coordinate. That's something you could easily notice if you look around, it would correspond to a shrinking universe, and our universe is expanding.

The "you won't notice crossing the event horizon" troupe is true only in a very local sense. If you move around and observe the geometry around you, you can definitely tell you're inside a black hole.

[KolenCh]

As the black hole getting larger, it is more difficult to notice this difference (of crossing the event horizon or “observe the geometry around you”.) and as we are talking about the whole visible universe being inside a black hole, we are in this extreme large scale.

Also, I’m not sure why you’re arguing about the radial coordinate being time-like. You can only measure in your own local reference frame. You wouldn’t necessarily be able to transform between your own local reference frame to the blackhole’s if you don’t know you’re in one.

The universe as a black hole is actually a very old idea: https://en.wikipedia.org/wiki/Black_hole_cosmology

I’m not saying we are in one, but I’m saying it is not as obviously false as you might be arguing.

[dustingetz]

https://www.reddit.com/r/askscience/s/vwCegmNdOE ?

[machina_ex_deus]

The fact that radial coordinate is timelike inside the event horizon doesn't change when you change coordinate systems. The radial direction remains timelike in kruskal coordinates. Direction being space like or time like is independent of coordinate system.