Physicists Simulate a Mini‑Universe and Observe Time Emerging Without an External Clock
A Birmingham team cooled 24,000 atoms to near absolute zero and showed that a form of time can arise from internal particle dynamics alone.
Building a Laboratory Cosmos
What a thrill to watch a universe in a bottle! At the University of Birmingham, Professor Giovanni Barontini assembled a cloud of roughly 24,000 atoms and cooled them to just a few billionths of a degree above absolute zero. At such frigid temperatures, quantum effects dominate, allowing the team to explore behaviors that are otherwise hidden.
The atoms were trapped inside a meticulously engineered quantum system that remained isolated from the outside world. Two laser beams of different frequencies formed a thin barrier, splitting the cloud into a “bright” (observed) region and a “dark” (unobserved) region. Although the overall setup was sealed, atoms could still migrate between the two zones.
Simulating Cosmic Expansion and Contraction
The bright region underwent repeated cycles of expansion and contraction. The expansion phase served as a simplified analogue of the Big Bang, while the contraction mirrored a hypothetical Big Crunch. These are not literal recreations of cosmic events, but rather a quantum model that lets researchers probe the ordering of events without an external timepiece.
Time Emerging from Entropy
The breakthrough hinged on entropy, the measure of disorder in a system. By monitoring how entropy evolved as the atoms moved and the bright region expanded or contracted, the team could infer a directional flow that functions as a clock built from within the system itself.
This internal clock emerged naturally, demonstrating experimentally that “time” need not be a fundamental ingredient of reality but can arise from the relationships and changes among particles.
Theoretical Implications
The experiment offers tangible support for ideas stemming from the Wheeler‑DeWitt equation, which describes a universe as a single, unchanging quantum state lacking an external time variable. Barontini’s work shows that even in such a timeless framework, a sequence of events can be reconstructed through internal dynamics.
Seeing time pop into existence inside a lab‑crafted universe is nothing short of exhilarating.
