Time from Disorder: How Atoms Revealed an Internal Clock ⚡ экспресс
In an experiment with an ultracold Bose condensate (a state of matter at extremely low temperatures), the trap was split by an optical barrier into an observed and an unobserved part. Inspired by ideas from quantum gravity, where time can disappear, an "entropic time" was built from coarse-grained entropy (a measure of disorder) and shown to order events in the observed part during repeated expansions and contractions of the cloud. Moreover, they derived a Schrödinger equation that operates with this internal time and reproduces the system's evolution. This is the first rigorous laboratory test of relational models of time, where time is not imposed from outside but emerges from internal processes—much like the plot of a movie isn't determined by a stopwatch but by the sequence of scenes.
Scientists took a cloud of atoms, colder than space, and cut it in half with a laser. One half was in plain sight, the other hidden. Instead of clocks, they measured the growth of disorder—entropy. Through it, all events lined up in a clear chain, even as the visible part expanded and contracted. Disorder worked like clock hands: the greater the chaos, the further in time. In a room without windows, growing disorder is the only sign of time's passage. Based on the same principle, entropy made it possible to write an equation describing the hidden part—the shadow found its voice. The idea was predicted by John Archibald Wheeler and Bryce DeWitt back in the 1960s: time is not absolute, it arises from relationships. Now it's an experimental fact. This approach paves the way to understanding time inside black holes, at the moment of the Big Bang, and wherever spacetime is curved to its limits.
🎯 Disorder in a closed system never decreases—that's what gives time its direction from past to future.