“Work gives you meaning and purpose and life is empty without it.” -Stephen Hawking
Throw a book into a black hole, and the information must somehow wind up inside. Same goes for a star, a planet, or even a single proton: that information must be maintained. But allow enough time to pass, and quantum theory and general relativity, combined, predict something troubling: that black hole will decay, and none of the information will come out in the decay products.
In physics, that’s what we call a paradox. Every individual quantum process affecting a particle and its interactions should be time-reversible, but if we run the clock backwards on black hole evaporation, that’s an impossibility. The worst part of the information paradox is that every proposed solution has problems that may be even greater than the paradox itself.