The space station represents an environment where weird physics can thrive. And in this case, some of those physicists are particularly interested in the Bose-Einstein condensate. It's an exotic state of matter where, when certain particles get to near-zero temperatures, they begin to act like waves. By doing experiments in orbit that can't be done on Earth, scientists hope to find new insights that will lead to powerful gravity detectors, precise atomic clocks, and much more.
The is made of all bosons, elementary particles that form the "glue" of matter. A Bose-Einstein condensate causes bosons, when at low temperature, to congeal together into one larger mass with many of bosons sharing the lowest quantum state and acting more like waves than particles. The condensates, which were first theorized in 1924, usually exist only at extremely low temperatures. When they were first found in 1995, they were called the holy grail of cold-matter physics by Oxford physicist Keith Burnett, and they are still opening doors to new exploration of physics. "Instead of being an end point, it turned out to be the beginning of an incredibly rich field, and one of the most vibrant areas of physics research today," says Robert Thompson, Cold Atom Laboratory lead scientist.
The problem with Bose-Einstein condensates is that they're fleeting. In ground-based laboratories, they're often gone within a second. That's where the Cold Atom Laboratory comes in. The microgravity environment of the ISS will allow the condensates to flow more freely. "You don't have to hold the atoms up under their own weight—they're sort of free-floating," says project manager Anita Sengupta.
And inside the facility will be a vacuum chamber that creates the ultra-cold environment. As opposed to the 1-second life span of some of the particles in ground-based laboratories, the Bose-Einstein condensates will be visible for up to 10 seconds—long enough to understand their behavior, in observational terms.
Here's how it will work: An electrical current will run through salts containing the element rubidium. This process will give off the desired isotope, rubidium-87, which can exist in a boson state, and then gather together to produce Bose-Einstein condensates. The condensates will then be trapped in optical laser fields. In the ultra-cold state, they'll stop bouncing around "like billiard balls," as Sengupta puts it, and start acting more like waves.
Once this behavior starts, scientists will be able to study this weird matter in ways impossible before. The discoveries made could provide researchers with powerful new tools: atom lasers that build on existing laser technology. Ultra-precise could be used for research near Earth and far into deep space by using condensates to measure precise wavelengths of light and other subtle atomic behavior.
"Just looking at ultra-cold atoms in this new parameter-space, we expect new phenomena to appear," Thompson said. "The field has a history such that when you open up a new parameter-space, you make new discoveries."
Because of the environment of the ISS, the Cold Atom Laboratory itself can be made fairly cheaply. And by building it, Thompson says, they'll be able to lay the groundwork for further Bose-Einstein-condensate research, and use what they find to develop a new generation of quantum sensors that will allow researchers to see gravity, allowing them to do things like measure the effects of global warming on ice sheets on Earth and peek beneath the frozen-ocean surface of Europa.
"Right now, the space station lets us do inexpensive proof of principal technologies," Thompson said. "But it also allows us to do cutting-edge science that would be difficult or impossible to do on any other space platform."