PeterDonis's latest activity

But those hypersurfaces are not geodesic hypersurfaces, so it's not clear that an "intrinsically flat" object can be embedded in them...

Yes, agreed. But how far it is deformed, under a given stress, depends on how strong the material is. A stronger material will deform...

Claim: There is no difficulty defining a congruence of world lines representing a piece of paper far from a BH, that then has each...

You have forgotten the relativity of simultaneity, which is less popularised than length contraction and time dilation, but probably...

That's correct. Note, though, that when you have a star in the center instead of a black hole, the spacetime geometry inside the star is...

First, you should say flat spacetime and curved spacetime. Those are the invariants. Second, while paper made out of the ordinary...

Some additional cautions may be stated: A paper so oriented is not inertial, so you have to imagine some force holding it in place...

That's not what I said. What I said is that, if you're observing from a distance objects that are at rest fairly close to a black hole's...

Thread reopened after a post with an unacceptable reference (ChatGPT) has been deleted.

Not if the conditions are the same. But what someone very distant observes won't be easily interpreted as "I'm seeing non-Euclidean...

If the paper were oriented radially, then yes, you would be able to draw a triangle on it whose angles would not add up to 180 degrees...

It depends on how the paper is oriented and what its state of motion is. But for a piece of paper of ordinary size and a black hole of...

Yes. The coordinates don't matter; the model is the same regardless of what chart you use. The Kruskal chart is useful because it...

There is a mathematical model in which that's true, but it's not one that is physically realized in our universe. No, because in the...

Why would it? Tangential motion doesn't affect the normal force. The direction of the acceleration vector does, yes. But the magnitude...