The Double Slit Experiment

There's no way to explain that with particles. People thought, well, look, this is something that waves do and light is doing it. So light must be a wave. In fact, there's even famous cases where they said, well, you know, if light is a wave, then, you know,. You would get this crazy effect. That was the early 1800s. The question was settled. We knew forever light was a wave. And we still didn't know what was it waving through? I think that's a big debate in pastry science still though.