rainbows

My college roommate and I recently held a long discussion which started and ended with quantum mechanics. Topics included a circuit which can detect single electrons but which had multiple routes the electron could take upon exit. His story told that he had been rewarded with a guided tour of some rather rare sashimi in Japan. A Japanese presentor had been trying to explain a circuit behavior to a Russian questioner. The Russian was trying to ask how the single electron could be affected by the destinations beyond all of the multiple outputs. My friend helped bridge the communications gap by clarifying that the wave-function of the electron is sensitive to all of the possible paths it might take.

We ended up back at the same issue as we discussed the simpler to demonstrate two-slit experiment. Anyone can do that experiment and see that each electron or photon must actually go through both slits in order to produce the interference pattern at the detector. If you try to ask which way it went, or if you block one slit, you don't get the interference pattern.

In astronomical optics we routinely rely on what is effectively a setup with thousands of slits. A diffraction grating is a surface with many finely spaced grooves or slits. Each photon effectively travels through every one of those paths, and the result is a spectrum, a rainbow -- the tool with which we analyze and understand the structure of the universe.

If you close off the possibilities you don't get the rainbow, you just get a mush of unsorted light.

Our discussion ended as we realized that human psychology shares a lot of characteristics with quantum mechanics. Don't prematurely or unnecessarily block off any paths. Make sure to keep conscious of the fact that there are still many paths, and keep open the option for exploring all of them. If you don't, the result is nowhere near as beautiful.