A closer look
At a fraction of a degree above absolute zero, atoms start behaving like bizarre, fragile balloons. Physicists create ultracold Rydberg molecules by hitting a super-chilled rubidium atom with a laser, kicking its outer electron so far away from the nucleus that the atom becomes thousands of times larger than normal. This sprawling, ghostly electron shell can casually swallow a neighboring, normal-sized atom, creating a bizarre molecule with a bond so incredibly weak that room-temperature heat would instantly shatter it.
