The Quest for Unity Is Not Something Physics Is Cut Out to Do
In physics, we like theories that are simple and broad-ranging. By “simple,” physicists usually mean a mathematical theory that rests on as few postulates as possible; by “broad-ranging,” we mean theories that can describe a wide class of phenomena, even when apparently not related. A quintessential example is Einstein’s theory of general relativity. Resting on a handful of simple principles, it successfully describes planetary orbits in this (and any) solar system, black holes, gravitational waves, and the expansion of the universe.
When theories are simple and broad-ranging, physicists call them “beautiful.” Nobel laureates Steven Weinberg and Frank
