[drudman]

Quantum weirdness is a huge trip. Three years ago, Daryn and I got drunk and talked for hours about it, and we were both pretty freaked out. Delayed double slit experiment might just be the King of quantum weirdness.

The idea is you take a card and put two small slits in it, very very close to each other (we're talking microscopically, the distance between the slits is only about 1000x the wavelength of the light you're going to shoot at it) and you shine light at it. Cover one or the other slit, and you get a single cone of light shining through the open slit. If light were like a particle, when neither slit was covered, one would expect to observe a solid band of light, brightest in the middle where the two light cones overlap. Instead, you get alternating bands of light and dark, like you would if you used ripples of water instead of light. This indicates that light sometimes behaves like a wave.

That was revolutionary, but what is shocking is if you fire individual quantum particles, instead of a steady stream of them. In 1989, some guys from a Japanese electronics company (Hitachi?) fired individual electrons instead of photons. Very oddly, the intereference pattern still showed up! This is highly weird, because with only one electron passing through at a time, how could there be any interference?