超冷气泡（粉红色）

Since the days of NASA’s Apollo program, astronauts have documented (and contended with) how liquids behave differently in microgravity than they do on Earth – coalescing into floating spheres instead of bottom-heavy droplets. Now, researchers have demonstrated this effect with a much more exotic material: gas cooled to nearly absolute zero (minus 459 degrees Fahrenheit, or minus 273 degrees Celsius), the lowest temperature matter can reach.

Using NASA’s Cold Atom Lab, the first-ever quantum physics facility aboard the International Space Station, researchers took samples of atoms cooled to within a millionth of a degree above absolute zero and shaped them into extremely thin, hollow spheres. The cold gas starts out in a small, round blob, like an egg yolk, and is sculpted into something more like a thin eggshell. On Earth, similar attempts fall flat: The atoms pool downward, forming something closer in shape to a contact lens than a bubble.

In this image, inside NASA’s Cold Atom Lab, scientists form bubbles from ultracold gas, shown in pink in this illustration. Lasers, also depicted, are used to cool the atoms, while an atom chip, illustrated in gray, generates magnetic fields to manipulate their shape, in combination with radio waves.

Learn more: Ultracold Bubbles on Space Station Open New Paths for Quantum Research

Image Credit: NASA/JPL-Caltech

自从NASA的阿波罗计划开始，宇航员们就已经记录了液体在微重力环境下与在地球上不同的行为——它们结合成漂浮的球体，而不是底部重的液滴。现在，研究人员用一种更奇特的材料证明了这种效应：气体冷却到接近绝对零度（零下459华氏度，或零下273摄氏度），这是物质可以达到的最低温度。

利用NASA的冷原子实验室（国际空间站上第一个量子物理设备），研究人员提取了冷却到绝对零度以上百万分之一度以内的原子样本，并将其塑造成极薄的空心球体。冷气体开始形成一个小而圆的斑点，像蛋黄，然后被雕刻成更像薄蛋壳的东西。在地球上，类似的尝试失败了：原子向下聚集，形成的形状更接近隐形眼镜，而不是气泡。

在这张图片中，在NASA冷原子实验室内，科学家们用超冷气体形成了气泡，在这张图中以粉红色显示。图中还描绘了激光用于冷却原子，而以灰色显示的原子芯片结合无线电波产生磁场以控制其形状。

了解更多：空间站上的超冷气泡为量子研究开辟了新途径

图片来源：NASA/JPL-Caltech