From the days of NASA’s Apollo program, astronauts have written (and argued) how the fluid behaves differently in microgravity than on Earth – it converts into a floating globe instead of heavy droplets. Researchers have shown this effect very unusual: cooled gas is almost entirely zero (minus 459 degrees Fahrenheit, or minus 273 degrees Celsius), the lowest temperature possible.
Using NASA’s Cold Atom Lab, the first quantum physics center in the International Space Station, researchers took samples of cool atoms up to a million degrees above zero and molded them into tiny spheres. Cold gas begins in a small, circular area, like an egg yolk, and is carved into a bit of eggshell. On Earth, similar efforts fall: Atoms collide to the ground, forming something closer to the contact lens than the bubble.
The milestone – described in a new online paper published Wednesday, May 18, in the journal Nature – is only possible in the microgravity space of the space station.
Cold bubbles can eventually be used in new experiments with something even more unusual: the fifth form of the substance (different from gases, liquids, solids, and plasma) called Bose-Einstein condensate (BEC). At BEC, scientists can look at the quantum properties of atoms on a scale that is visible to the naked eye. For example, atoms and particles sometimes behave like solid objects and waves – a quantum material called “wave-particle duality.”
Work does not require the help of an astrologer. Cold bubbles are made inside the tightly closed Cold Atom Lab vacuum chamber using magnetic fields to treat the gas into various forms gently. And the lab itself – about the size of a small refrigerator – is operated remotely from the JPL.
Giant bubbles are about 1 millimeter wide and 1 micron thick (one thousand millimeters, or 0.00004 inches). They are so tiny and molten that they are made up of thousands of atoms. A cubic millimeter of air on Earth contains somewhere about billions of molecules.
“These are not like your usual soap bubbles,” said David Aveline, lead author of the new project and a member of the Cold Atom Lab science team at NASA’s Jet Propulsion Laboratory in Southern California. “We know nothing in Nature as cold as the atomic gas produced at the Cold Atom Lab. So we start with this very different gas and learn how it behaves when it is formed in very different geometries. And, historically, when something is used in this way, very interesting physics can emerge, as well as new uses.”