Wave-particle duality is a cornerstone of __quantum mechanics__, which is our modern theory of how subatomic particles behave. The duality states that all particles (in fact, all objects) have a wave-like property associated with them. While most standard interpretations of quantum mechanics treat this wave-like property as a neat mathematical trick for calculating the probability of a particle being in one place or another, some more radical interpretations elevate the wave to a real entity that exists just as much as particles do. One of these interpretations, known as the pilot-wave theory, posits that every interaction in the universe can be described by a single set of equations — if only we could figure those out.

### The original waves

In 1924, French physics doctoral student Louis de Broglie proposed that matter has a wave-like property. De Broglie was inspired by the discovery of wave-particle duality in light. For centuries, physicists had debated whether light was made of tiny particles or some sort of waves. In the mid-1800s the debate seemed to be settled with James Clerk Maxwell’s discovery of the electromagnetic field, and his realization that light was made of electromagnetic waves, according to “The History of Quantum Mechanics” (CreateSpace Independent Publishing, 2017).