Imagine the Earth gets swallowed by a black hole. Then, like all black holes, this one slowly evaporates away as particles radiate from its event horizon, until—poof—there’s nothing left.
What happens to everything that has fallen in? Has it just been deleted from the universe? Could information somehow escape from behind the event horizon? Or did it never truly fall in in the first place?
Ultimately, no one knows—and each one of these three unlikely answers breaks physics as we know it.