In Plato’s Republic, Socrates is conducting a dialogue with some friends that attempts to define ‘justice’. Along the way they determine that a just person would be one who is on a constant journey to find Truth. But what is Truth? According to Socrates (or technically Plato, I guess), Truth could be found at the end of the Divided Line.
In 1976, Stephen Hawking calculated that when a black hole forms, it starts losing mass by radiating energy. Eventually, the black hole kind of dissolves. The problem with that is a fundamental law of Quantum Physics, which says that all ‘information’ must be preserved, and can never be destroyed. (You can consider ‘information’ to mean whatever makes any bit of matter what it is. Like the blueprint of an atom, in a way.) Hawking’s results showed that the energy radiating from the black hole contains no information about the matter in the black hole, and that once the black hole has dissolved, nothing is left. He presented his findings, and for over 25 years, people have been trying to solve this paradox.