Deep in the mantle, a branching plume of intensely hot material appears to be the engine powering vast volcanic activity.

For over two decades, physicists have pondered how the fabric of space-time may emerge from some kind of quantum entanglement. In Monika Schleier-Smith’s lab at Stanford University, the thought experiment is becoming real.

Investigations of the simplest possible clocks have revealed their fundamental limitations — as well as insights into the nature of time itself.

The five-decade-old paradox — long thought key to linking quantum theory with Einstein’s theory of gravity — is falling to a new generation of thinkers. Netta Engelhardt is leading the way.