Try picturing an electron. What do you see?

At some point in your physics education, you might have learned to think of elementary particles as infinitesimal points. But this picture, while adequate for most of classical mechanics and electromagnetism, completely breaks down in the realm of quantum mechanics, where we learn that particles evolve in probability waves, and have intrinsic properties like spin for which there exist no classical counterpart.

So you learn to think like a 20th century quantum mechanic, calculating probability waves swashing in boxes and convincing yourself that whenever you measure a particle, its probability wave instantly collapses onto a single set of states. Yet this still cannot be the whole picture, because special relativity, the other revolution in 20th century physics, tells us that the fastest speed information can ever travel at is c, roughly 300 000 000 m/s, the speed of light. Instantaneous collapse is not possible.

In their own home turfs, quantum mechanics and special relativity are remarkably successful.

Two theories collide

This post owes its inspiration to the lectures Bea Noether gave to me as part of the physics directed reading program. See my other notes here.