Experiments on Earth have cooled samples to extremely low temperatures, but there’s only so much you can do in a normal room. As you approach absolute zero — the coldest possible temperature, and the point at which all motion stops — radiant heat from the environment keeps the magic number just out of reach. Scientists believe the CAL will be able to get closer than ever before to absolute zero, and locating it aboard the ISS will make the spooky quantum properties of the universe easier to study.
The CAL uses magnetic fields to suspend samples, allowing lasers to cool them to within fractions of a degree of absolute zero. That’s -459.67 degrees Fahrenheit (-273.15 degrees Celsius or 0 Kelvin). Studying atoms at temperatures near absolute zero allows scientists to understand and test their quantum mechanical properties. The atoms have almost no entropy, so quantum states last longer and encounter less interference from the environment.
In particular, researchers are interested in producing Bose-Einstein condensates. This is a state of matter in which atoms occupy the same low-energy quantum state and behave like a single wave rather than particles. Experiments on Earth can produce Bose-Einstein condensates (scientists won the 2001 Nobel prize in physics for creating them), but gravity causes them to sink to the bottom of the container and dissipate. In orbit, these waves might last as long as 10 seconds.
This environment will also support the formation of Efimov physics, which relates to the quantum interactions among three particle groups. At near absolute zero, molecules consisting of three atoms can be produced that are substantially larger and easier to study than usual.
NASA has completed design and construction of the CAL in just a few years by using all off-the-shelf hardware and software. Still, it’s a complicated apparatus that required extensive testing. The CAL was initially scheduled to go up to the ISS in early 2017, but testing setbacks at NASA’s Jet Propulsion Laboratory caused delays in the mission. An exact delivery date isn’t set, but it’s expected to be within the next several months.