A research student at Princeton, Bekenstein suggested a black hole’s event horizon area was a measure of its entropy, or disorder. That, in turn, would mean that black holes must emit energy, though they previously weren’t thought to emit anything at all. Stephen Hawking disagreed with this theory and was annoyed when, by his own calculations, he realized it must be true (especially given that he had already published a paper about how the theory could not be true). Later, Hawking accepted Bekenstein’s theory, illustrating an example of the importance of humility.