What is common knowledge in your field but shocks outsiders? It's been over a hundred years since we first realized that quantum mechanics is a thing, but we still don't actually understand what it *means* about the nature of our universe. (Though we can predict the output of experiments fine.)

The Greek atomists thought up stochasticity at the quantum scale, entirely over dinner & drinks, and a few hundred years before jeebus, because they didn’t like either supernatural forces or determinism.

"If you think you understand it, you don't.""If you think you understand it, you don't."

As an optician, "My glasses are always sliding down now matter how much I tighten them!" The glasses have been so over tightened they are pitched forward forcing them to slide off. Loosen the bend to make them sit down where they should and stop the sliding down. There are SO MANY in opticianry.

It’s waves all the way down

This drives me up a wall more often than I like to admit. A PARTICLE AND A WAVE?!? THE SLIT EXPERIMENT?!?