Bob Kanefsky interview cont'd

Quantum

I used to understand exactly where the iridescent colors in soap bubbles came from: the film is so thin that light that bounces off the near surface can be just half a wavelength out of phase with light that passes through and then bounces off the far surface, and they cancel out -- or they can be in phase and reenforce each other, depending on the exact thickness of the soap film at each point. Since each color has its own wavelengths and white light contains all colors, the bubble reflects different colors depending on how thick it is. That's what I learned in high school, and it fit with my own bathtub observations when I was a kid, that dark spots appear just before it pops, as if they were thin patches. Then I read a book on quantum electrodynamic theory, which spent a whole chapter explaining how quantum theory accounts for soap bubble colors. I didn't understand that at all. So now I no longer understand why bubbles are colorful. Although simpler theories are supposed to be better in science, I guess the only thing that counts is how simple the mathematics are, not whether the model resembles and everyday familiar example. The universe didn't know we would be living in a world of pond ripples and vibrating strings when it made up its rules. The wave model is easy to understand, but it doesn't explain other non-bubbly observations, like individual photons being detectable, or why the fluorescent leg-band I wear when bicycling can step pure blue light down to orange.

At least I no longer feel compelled to give kids a physics lesson while I'm blowing bubbles.