Light is one of those things people have been thinking about for thousands of years. Aristotle the realist thought that people see because rays of light come out of our eyes.

I thought those ancient Greeks were supposed to be smart?

There are some problems with Aristotle's theory, but it's not a bad start. It would explain why some people see better than others, and it's how bats sense things with sound: making squeeks and listening for the echoes. Besides, how do you think Superman's x-ray vision works, hmm?

Anyway, once people realized that rays of light came from things like the sun and fire, they started trying to find out the properties of light. You know the jokes that start out, "There are two kinds of people..."? Like, there are two kinds of people, people who think there are two kinds of people and people who don't? That's a favorite way in science to categorize things: find mutually exclusive properties. By the 1500s, people agreed that light was not a ray. There were too many phenomena that the ray theory could not explain. But there were people who thought light is made of waves, and people who thought light is made of particles. What makes that a dichotomy?

OK, now that I know what a dichotomy is, why can't something be both wave and particle?

I'm glad you asked. Start with "What's the Problem Here?" and work your way down.

Fast Cars, Sex, Drugs, Rock 'n' Roll, and ELFs: The Lowlife of the Electromagnetic Spectrum