Blue Collar Scientist

The webcomic xkcd today simultaneously tells us why Mythbusters is real science, and slams string theory in the process. It is not to be missed, and I agree with both sentiments.

The double-slit experiment is probably the weirdest scientific result in history, and certainly the strangest one that I’ve personally witnessed. Some classroom discussion of the experiment led me to do a little looking for an explanation of it, and I happened upon this cartoon which I thought did a pretty good job:

Some of the questions that are usually raised by high-school students trying to grok this experiment are along the lines of “why do we all see the same stuff, since we are different observers.” There are a bunch of prose answers to this question (as opposed to mathematical ones. One of my favorites is that asking why we don’t see quantum effects in everything is similar to asking why human bodies don’t move around in response to Brownian motion, or why the Coriolis force doesn’t control the destiny of toilet bowl flushes. This has the benefit of giving the students a chance to think about phenomena on different scales, and also makes it possible to change the subject, which isn’t always a bad idea considering that I’m no expert on quantum mechanics.

A somewhat better explanation is that whenever there is a quantum phenomenon, the first observer collapses the waveform. Don’t be intimidated by the terminology - a “waveform” is just a list of all the possible states that the quantum particle might be in. When the waveform “collapses,” the list becomes one item long. The first observer does the collapsing, and what subsequent observers see will be consistent with that first observation.