Back in 2007, when I'd just moved to Los Angeles, I drove up to San Francisco to visit its signature science museum, the Exploratorium. There were lots of cool exhibits, but my favorite was the cloud chamber. Yeah, yeah, I know it's old technology dating back to 1895 -- former SciAm editor George Musser Jr. even built his own DIY version. But this was the first time I -- not being a scientist -- had the chance to see a cloud chamber up close and personal, and watch the telltale wispy little white lines -- a.k.a., cosmic ray tracks, or trails of ions -- flash in and out of existence, looking for all the world like tiny jet contrails.

Confession: I stared at the darn thing for a good 15 minutes solid, sufficiently rapt at the intricate subatomic ballet playing out before my eyes, that a few people joined me out of curiosity, before shrugging and moving on to something a bit showier. Finally, one guy asked me what the hell was so fascinating. And I told him it was like a tiny window onto the subatomic world, concrete evidence that while we can't see such things with the naked eye, nonetheless, our universe, at this itsy-bitsy size scale, is teeming with activity. It was quantum poetry in motion.

Not everyone appreciates the beauty of a simple cloud chamber, but Alexis Kirke is a fellow aficionado. He's the composer in residence at the Plymouth Marine Institute in England, a research fellow at Plymouth University, and holds PhDs in both the arts and technology. So it's not surprising that much of his multimedia work (across multiple platforms) has a scientific bent -- including "Cloud Chamber," a duet for violin and "live" subatomic particles. Yeah, you read that right: subatomic particles. The performance requires not just a human violinist, but a working cloud chamber with a camera mounted over it. The camera records the tracks left by cosmic rays and converts them into synthesized music.

I first wrote about Kirke's work back in 2011 for Discovery News, when he debuted the piece. And now there's a documentary short feature based on a recent performance of "Cloud Chamber" in San Francisco at the California Academy of Sciences.

The cloud chamber was invented by Scottish physicist Charles Thomas Rees Wilson in 1895 at Cambridge University's famed Cavendish Laboratory. Wilson was interested in the weather and wanted a means of reproducing the condensation of clouds in the laboratory. This happens as the result of a sudden expansion of the volume of some closed vessel filled with air saturated with water vapor. Said expansion causes a drop in temperature, and makes the air supersaturated, resulting in condensation. And he brought the tools of physics available at that time to bear on the challenge. He focused on how ions serve as nuclei for water droplets, and even began photographing the formation of those droplets.

By 1910, Wilson had figured out he could use his cloud chamber device to detect charged particles, since they would leave a trail of ions -- and water droplets -- as they passed through the gas in the chamber. He took the very first photographs of the tracks left by alpha and beta rays.

Both alpha and beta particles have distinctive tracks: the former is broad and straight, while the latter is thinner and more easily deflected by collisions with other particles. Apply a uniform magnetic field across the cloud chamber, and positively and negatively charged particles will curve in opposite directions. Carl Anderson used one to study cosmic rays and inadvertently discovered the positron in the 1930s, snagging himself a Nobel Prize.

For "Cloud Chamber" performances, Kirke uses a cloud chamber containing radium 225. Two of his colleagues, Anna Troisi and Antonino Chiaramonte, worked with center head Eduardo Miranda to device a visual-recognition-to-sound interface that they dubbed the Cloud Catcher, capable of functioning in real time. Per Wired:

“In the duet, a camera above a cloud chamber follows the particle tracks and converts them into synthesized music, which accompanies the violin…. An amplified version of the violin part was also sent to an electromagnetic field system positioned near the particles. Thus [the violinist's] playing creates a variable force field in the chamber, influencing the way the particles behave. This ensures that the duet between radioactive particles and violinist is as dynamic as possible."

Kirke's other projects include "Sunlight Symphony" (in which he converted a building into a musical instrument played by the rising sun); "Sound-Wave" (in which he turned a giant wave-tank into a musical instrument); and "Insight," in which Kirke -- who suffers from a visual condition called palinopsia -- simulated his own hallucinations live on an iPad, which were then converted into sound. He also wrote and directed a short film, Many Worlds, featuring a human version of a Schroedinger's cat experiment. (There are four possible scripts and four possible endings; biosignals collected from the audience as they watch determine which version the audience will see.)

"Cloud Chamber" is still my favorite. I hope you enjoy it, too.