Over at Uncertain Principles, Chad has started up a series on cold-atom physics. I do a lot of the very same things since I also work with cold atoms; we’re well past the time in the history of this area of physics where simply getting atoms cold is the research. The variety in the research these days is in what you do with the atoms once they’re cold (f’rinstance, I have ways of making them tock)

Here are the first three posts

Tools of the Cold-Atom Trade: Introduction

Tools of the Cold-Atom Trade: Light Scattering Forces and Slow Atomic Beams

Tools of the Cold-Atom Trade: Optical Molasses

But here’s the thing: photons are really cheap. A red laser pointer that you can get for next to nothing at your local office supply store will put out 1,000,000,000,000,000 photons per second.

I love the line “photons are cheap”.

I recall a time when I was showing off our atom trap at TRIUMF and discussing how we detect the atoms so that we know the trap is working (as opposed to the nuclear experiment we were doing), and there was a bit of a communication difficulty, because the nuclear physicist wasn’t used to thinking in terms of getting anything but one particle per atom to detect. But an alkali atom can scatter millions of photons per second (with the transition we were using, if you’re near resonance), which is the complementary part to “photons are cheap” that is important. I can’t think of a catchy description that I’d use, though. (Maybe “atoms are gregarious”?)