What the information paradox asks — does information falling into a black hole disappear, violating quantum mechanics

What the EPR paradox challenged — Einstein argued entanglement implied either hidden variables or nonlocality

EPR paradox questioned quantum mechanics' lack of locality and determinism

What Maxwell's demon thought experiment challenges — can information be used to decrease entropy

Maxwell's demon challenges the second law of thermodynamics by potentially decreasing entropy using information

What the Penrose-Hawking singularity theorems prove — singularities are inevitable in general relativity under certain conditions

Theorems assert black holes and singularities arise from gravitational collapse in spacetime

What the measurement problem asks — why does a quantum superposition collapse to a definite state upon observation

Quantum measurement problem: Superposition collapses due to observer interaction

What the arrow of time problem asks — why does time have a direction when fundamental laws are time-reversible

The arrow of time problem questions why entropy increases in one direction despite time-reversible laws

What Bell's theorem proved — no local hidden variable theory can reproduce all predictions of quantum mechanics

Bell's theorem disproved local hidden variable theories' ability to match quantum mechanics' predictions