Geniuses of the Cold
Mid-1990s Boulder was busy with activity. Fitness was king. Local businesses were prized. Hacky Sack circles and jam band opuses were ubiquitous anywhere students congregated.
Simultaneous to that, though, was something wholly different. Buried in the corridors of the JILA tower on CU’s campus, a breakthrough was purring along quietly. Professors Carl Wieman and Eric Cornell were making real what many physicists thought was only theory.
In the 1920s, Satyendra Nath Bose and Albert Einstein conceived of a new form of matter, which came to be known as the Bose-Einstein Condensate. A full explanation is beyond my pay grade, but in essence they put forth that, at extremely low temperatures, particles would begin acting less like individual pieces and more like a uniform wave. It’s what the high-level math said, anyway. At the time, few imagined that would ever be tested.
Wieman and Cornell saw things differently. Before that, however, it’s worth pausing for a quick refresher.
Temperature, for physicists, is a matter of particle behavior: when they are excited and moving rapidly, it’s called heat; when moving slower, it’s labeled cold. Greater excitement means more energy and mutable bonds between particles, less excitement the opposite.
As an example, compare hot air balloons to ice. Heating air within a balloon reduces density relative to the air outside of it, increasing buoyancy. Ice is a matter of water molecules cooling until they create strong, crystalline structures. In both cases, temperature and corresponding properties result from how much energy is present among particles.
Wieman and Cornell ran with that concept. Through a complicated system of magnetic “traps” and lasers, they coaxed rubidium atoms into slowing more than had ever been observed (the traps corralled atoms in place; the lasers, along with evaporative cooling, counteracted particle movement). In 1995, after much refinement, that system led to creation of the first Bose-Einstein Condensate.
So then, their JILA lab housed the coldest spot in the universe, at 170 nanokelvin (meaning 1.7 x 10-7 Kelvin), as close to absolute zero as had been recorded. For scale, remember absolute zero—the theoretical point at which no particle energy is present—is 0 Kelvin, or −459.67 °F. The Condensate was astounding enough that Wieman, Cornell, and Wolfgang Ketterle (who was on the same track using sodium atoms) were awarded the Nobel Prize for Physics in 2001.
As happens, others eventually surpassed that work. In 2003, a team at MIT reached a temperature of 450 picokelvin (equal to 4.5 x 10-12 Kelvin) in their lab. This pushed particles to such a low excitement state that Earth’s gravity became a stumbling point, so much so that, as of January 2014, NASA made plans to create a Condensate on the International Space Station. They hope to reach low temperatures somewhere between 100 and 1 picokelvin in the near future.
Though subsequent achievements are impressive, it all began with Wieman and Cornell’s breakthrough. For eight years, Boulder housed a spot edging on absolute zero, something the universe itself can’t produce naturally, as far as we know. Practical applications of the Condensate are still to come, but it’s no less awe-inspiring. Between 1995 and 2003, despite all the activity in our city, it was a small chamber in a laboratory on CU’s campus that had the most heat… non-scientifically speaking, of course.