TIL an Event Horizon is a boundary in space time beyond which no signal can ever reach a given observer

If you think black holes are crazy white holes will blow your mind too.

https://www.npr.org/2023/10/31/1209487538/book-review-carlo-rovelli-white-holes

I.e. black holes exist.

Fun fact: time and space basically switch meaning, mathematically, when crossing said boundary.