Quantum mechanics is our most successful physical theory. Created to account for atomic phenomena, it has a vast range of applications extending well beyond the atomic realm, from predicting the abundances of the light elements created a few minutes after the Big Bang to understanding the properties of semiconductor materials that are the basis of advanced information technologies. Quantum mechanics is also successful in its exquisitely accurate
Black holes could be the key to a quantum theory of gravity, providing a deeper understanding of how reality, space, and time works. They are regions of space from which even light can't escape, and have fascinated physicists since their theoretical predictions, which date back to the early 20th century. The existence of black holes forces physicists to think about both quantum theory and general relativity together, highlighting the need for a unifying theory or quantum gravity.