If one more cold or flu virus hits our household before the end of 2009, we might officially place ourselves under quarantine, or opt to live in one of those plastic bubbles to avoid picking up any more pesky illnesses that sap our energy and reduce productivity to the point where taking out the garbage is considered a major achievement. Seriously, I've come down with more colds this past year than in the five previous years combined. Fortunately, Jen-Luc Piquant amuses herself by trolling the Interwebz for cool stuff, and knowing how much I love science-themed art, or art based on science (hell, even science based on art!), she pointed me to a post on Symmetry Breaking, earlier this year that I inexplicably missed, featuring the latest work of artist Roshan Houshmand. Houshmand has created a series of paintings based on the wispy trails left by subatomic particles as they move through bubble chambers.
It's not the first time Symmetry has featured Houshmand. Back in 2007, the magazine published a nice little feature about the Iranian-American artist's work. Although many family members had science-based careers engineers or medical professionals, Houshmand earned degrees in fine art. One year, her uncles were visited her in upstate New York, and she took them to hear string theorist Brian Greene give a public lecture. Greene's talk blew her away, particularly the notion that there might be 11 dimensions to reality. 'Somehow this statement produced a tremendous feeling of relief in me, and allowed me to redefine my perspectives on life," she recalled.
The experience inspired her to spend the next five months immersing herself in physics books. Somewhere in that process of self-education, she came across photographs from bubble chambers, taken in the 1960s and 1970s at Brookhaven National Laboratory and at CERN. She became fascinated by the patterns, the tracks of otherwise invisible subatomic particles traveling through the liquid hydrogen in the chambers, and this inspired to create her series of "Event Paintings," beginning in 2005. "The images are extremely sophisticated and yet there's something so pure and primal about the movement of the forms," she told Symmetry.
Houshmand starts with the raw printouts of the images and picks those that "speak" to her in some way artistically. She uses "cold black" paint as a primer (actually a really dark blue), sketches the outlines of the event with chalk, and then colors in that sketch with paints. The result is some truly dazzling works of art, based on the movement of the tiniest building blocks of nature. How cool is that?
Finding ways to make the invisible, visible, is the reason bubble chambers were invented to begin with: scientists were looking for a means of detecting and imaging cosmic rays, first discovered by Victor Hess in 1912 during an ion chamber balloon experiment. Hess was expecting to find a decrease of ionization in the atmosphere with increasing altitude. Instead, he found just the opposite, and concluded there must be radiation entering our atmosphere from space.
Back then, there were no bubble chambers, but there were cloud chambers, 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, most notably discharge tubes. 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, not to mention evidence of how individual atoms and their electrons interacted. 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. Wilson chambers became all the rage in particle physics, leading to all kinds of exciting discoveries. The discovery of the positron in 1932 at Caltech occurred thanks to a Wilson chamber, garnering physicist Carl Anderson a Nobel Prize in the process. Wilson himself snagged a Nobel, too, for his invention of the cloud chamber.
I love cloud chambers, particularly the one on display at San Francisco's amazing Exploratorium science museum. There's even a handy Website with instructions on building your own. But cloud chambers had their limitations for research purposes, particularly as particle physics continued to advance. They were too small, for one thing, for use at large accelerators. And the liquid filling wasn't sufficiently dense to interact with a large number of highly energetic particles. It also had a slow cycle: the process of reactivating the cloud chamber took too long compared to the accelerator cycles.
Enter Donald Glaser, an American physicist credited with inventing the bubble chamber, which works on similar principles to a cloud chamber, except it is filled with a superheated liquid instead of a gas. The son of a sundries salesman, Glaser hailed from Cleveland, Ohio, and was a sufficiently accomplished musician that he played with the local symphony at age 16. But his real love was math and physics, and he went on to earn his PhD from Caltech in 1950.
Legend has it that while he was on the faculty of the University of Michigan, Glaser was chilling with colleagues over a cold beer, observed the stream of bubbles in his glass, and was inspired to build a device that could track subatomic particles with bubbles. Glaser himself later refuted this story; beer was not his inspiration, although he did use it as a liquid in early prototypes. His first device was a small glass bulb roughly the size of his thumb and initially filled not just with beer, but also soda water and ginger ale. He didn't have much success with those liquids at capturing the trail of bubbles left by subatomic particles. Then he built a small bubble chamber in 1953 filled with superheated liquid diethyl ether, augmented with a high-speed camera to record the very first tracks of cosmic rays. He won the 1960 Nobel Prize in physics for his achievement -- one of the youngest scientists to be so honored.
Today's bubble chambers are filled with, say, superheated hydrogen. Yes, hydrogen is normally a gas but if you keep it under pressure it will take the form of a liquid. Then you can release it ever so slightly at the moment particles enter the chamber, so that it becomes superheated. This happens because the energetic particles make the liquid boil as they pass through the chamber, creating a trail of bubbles in their wake. It's tough to detect the particles themselves, since they're gone within nanoseconds, but the bubbles expand on the order of microseconds -- enough time for photographs to be taken from multiple angles by a set of cameras, thereby giving scientists a 3D image of the particle's path. Then you just re-pressurize the chamber, and you're ready to detect the next batch of particles.
Glaser experimented with superheated liquid hydrogen, as well as xenon gas, after moving to the University of California, Berkeley, further refining his invention. In his first two years at Berkeley alone, he collecting nearly half a million photographs tracking the passage of particles through a newer, bigger bubble chamber built by his colleague, Luis Alvarez. This device was six feet long, compared to the inch-long bubble chamber Glaser first invented, and it could measure particle tracks every 14 seconds. Chalk up yet another Nobel Prize, this time for Alvarez, whose machine helped launch the era of big science in high-energy physics.
Ironically, both Alvarez and Glaser left particle physics after their triumphs. Some have speculated they became bored and a bit disillusioned with how automated the field had become. These days, it's all about trolling through massive amounts of data with supercomputers, hoping to find the telltale signature of a rare exotic particle. Everything is digitized, and modern detectors can record hundreds or thousands of particle bursts in just a few seconds. I think modern particle physicists still find plenty of excitement, creativity and innovation in their work -- it might be more automated, but creating and detecting a top quark isn't exactly as easy as a factory assembly line. But from the perspective of a man schooled in the craft of tabletop physics experiments, it was the end of an era.
Glaser went on to make his mark in the field of molecular biology, researching the evolution of bacteria, how cell growth is regulated, and the causes of cancer and genetic mutation. In particular, he found that certain mutations in Chinese hamsters caused the animals to be unusually sensitive to UV light; exposure to UV rays caused the mutated cells to turn into cancer cells. The same defects can be found in humans, giving rise to a rare cancer called xeroderma pigmentosum. (It's a kind of vampire cancer, in that if the sufferer avoids exposure to daylight, they can remain cancer free.)
He co-founded the first biotechnology company with two colleagues in the 1970s, correctly foreseeing the explosion in applying the fruits of molecular biology research to industry, particularly medicine and agriculture. And when even that lost its novelty, Glaser moved into neurobiology, specifically studying the human visual system and its perception of motion and depth. Glaser also used photo-analyzing equipment he'd originally developed for his bubble chamber to identify species of bacteria via computer scanning, so he brought a bit of automation to his new field as well. And while bubble chambers have been largely superseded in particle physics by later technologies such as spark chambers and wire chambers, they are experiencing some resurgence of interest in the ongoing search for dark matter particles.
All in all, it's been a richly rewarding and varied life for the man who build the first bubble chamber, even discounting the glories of a Nobel Prize. How many physicists can say their inventions have inspired artists to create paintings based on those inventions?