Most of us find it difficult to grasp the quantum world. According to Heisenberg’s uncertainty principle, it’s like observing a dance without being able to see simultaneously exactly where someone is dancing and how fast they’re moving—you always must choose to focus on one.

And yet, this quantum dance is far from chaotic; the dancers follow a strict choreography. In molecules, this strange behavior has another consequence: Even if a molecule should be completely frozen at absolute zero, it never truly comes to rest. The atoms it is made of perform a constant, never-ending quiet dance driven by so-called zero-point energy.