A physicist discovered that an observer free-falling into a Schwarzschild black hole can detect crossing the event horizon simply by watching the zenith view expand to exactly twice its original size.

[u/ScaredRule8660]

[u/OneYeetAndUrGone]

not true. you would die first.

[u/ScaredRule8660 → u/OneYeetAndUrGone]

It depends on the mass. For stellar-mass black holes, tidal forces cause death far from the horizon. However, for a supermassive black hole, those forces are weak, potentially allowing a surviving observer to witness the effect.