Time might emerge from disorder itself, not tick from outside
In Birmingham, physicists have glimpsed something ancient and unsettling: time not as the silent stage on which existence unfolds, but as a property that quantum systems generate from within themselves. By watching a cloud of ultracold atoms expand and collapse forty-four times, a team led by Giovanni Barontini constructed a working measure of time from entropy alone — no external clock required. The experiment does not dissolve the mystery of time, but it moves that mystery from philosophy into the laboratory, where it can at last be tested.
- Physics has long treated time as a given, but quantum gravity's equations have no natural place for it — a foundational tension this experiment was designed to confront directly.
- A Bose-Einstein condensate, split by a wall of light and cycled through forty-four expansion-recollapse sequences, became the arena for one of the most disorienting questions in science: can a system generate its own temporal order?
- By measuring entropy in the observed half of the condensate, the team built an 'entropic time' — a sequencing of events derived purely from internal disorder, with no reference to any outside clock.
- The entropic time metric worked: it successfully predicted quantum behavior through a reconstructed Schrödinger equation, validated consistently across all forty-four cycles.
- The results, published in Physics Letters A with open data, crack open a pathway toward experimentally testing quantum gravity theories — a domain long considered beyond the reach of any laboratory.
In a laboratory at the University of Birmingham, physicists have constructed time from scratch — not as a philosophical exercise, but as a measurable, testable phenomenon emerging from the internal disorder of a quantum system. The experiment centered on a Bose-Einstein condensate, a cloud of atoms cooled to near absolute zero and divided in two by a thin barrier of light. One half was observed; the other was left undisturbed. The cloud was then allowed to expand and collapse, forty-four times in succession.
The question animating this work is one physics has long deferred: what is time, really? Traditional frameworks treat it as a backdrop — fixed, external, assumed. But quantum gravity, the effort to reconcile quantum mechanics with Einstein's relativity, keeps colliding with equations that seem to have no natural place for time as we experience it. Theorist John Wheeler proposed decades ago that time might instead be relational — something that emerges from the interactions between parts of a quantum system rather than something imposed from outside. Giovanni Barontini's team set out to test that idea with real atoms.
The method was precise. By tracking the entropy of the observed sector, the researchers built what they called an entropic time: an ordering of events derived entirely from how internal disorder shifted as atoms moved between the two halves. A key discovery sharpened the approach — entropy in the denser sector proved directly proportional to atom count, giving the team a reliable backbone for their time metric. From this, they reconstructed an effective Schrödinger equation and tested its predictions against actual measurements. The match held across all forty-four cycles.
The implications extend well beyond the condensate. If a quantum system can generate its own temporal ordering from entropy alone, time itself may be an emergent property of sufficiently complex quantum systems — not a thread woven into the fabric of reality from the beginning, but something that arises within it. Causality and clocks remain intact; what changes is the deeper story of where time comes from. With their data made publicly available, the Birmingham team has opened a rare door: a controlled laboratory setting where the fundamental nature of time can now be experimentally interrogated.
In a laboratory at the University of Birmingham, physicists have done something that sounds impossible: they built time from scratch, watching it emerge from the internal disorder of a quantum system. The experiment involved a Bose-Einstein condensate—a cloud of atoms cooled to near absolute zero—that was split in two by a thin wall of light. One side was observed, the other left alone. Then the researchers watched the cloud expand and collapse, over and over, forty-four times in total. Each cycle offered a chance to test whether time could be something the system generated on its own, rather than something imposed from outside.
The question driving this work is ancient and unsolved: What is time, really? Physics has always treated it as a given, a stage on which events unfold. But quantum gravity—the effort to merge quantum mechanics with Einstein's relativity—keeps running into a wall. The equations that describe the universe at the smallest scales don't seem to have room for time as we experience it. Theorists like John Wheeler proposed that time might not be fundamental at all, but rather something that emerges from the relationships between parts of a quantum system. This experiment, led by Giovanni Barontini, was designed to test that idea in a controlled way.
The setup was elegant. The optical barrier divided the condensate into two sectors. By measuring the entropy—the disorder or randomness—of the observed sector, the team could construct what they called an entropic time. This wasn't time as a clock measures it. It was time as an ordering principle, derived purely from how the system's internal disorder changed. The researchers discovered something striking: the entropy of the bright sector, where atoms clustered, was directly proportional to the number of atoms present. This connection between entropy and atom count became the backbone of their time metric. As atoms moved between sectors, entropy shifted, and that shift could be used to order events in sequence.
What made this more than a theoretical curiosity was that the entropic time actually worked. The researchers used it to construct an effective Schrödinger equation—the fundamental equation of quantum mechanics—and tested it against what they observed in the condensate. The predictions matched the measurements. Across all forty-four expansion-recollapse cycles, the internally derived time metric consistently ordered events in the observed sector. The system had, in effect, generated its own clock from nothing but its own disorder.
The implications ripple outward. If time can emerge from entropy in a controlled quantum system, it suggests that time itself might be emergent in the universe at large. This doesn't mean your watch is wrong or that causality is an illusion. It means time might be a property that arises when you have a quantum system complex enough to have entropy, rather than something woven into the fabric of reality from the start. The work opens a door to testing quantum gravity theories experimentally, something that has long seemed impossible. The team published their results in Physics Letters A and made their data publicly available, inviting other researchers to scrutinize and build on what they found. The question of what time is remains open, but now there is a laboratory where that question can be asked and answered.
Notable Quotes
Time can be constructed not as an external parameter, but as an emergent property of entropy within a quantum system— Research findings from University of Birmingham team
The Hearth Conversation Another angle on the story
So they didn't measure time in the usual way—with a clock?
No. They constructed a measure of time from entropy alone, from how disordered the system became. It's time as an ordering principle rather than a ticking parameter.
And this ordering actually worked across multiple cycles?
Yes, forty-four times the condensate expanded and collapsed, and the entropic time consistently ordered events in the observed sector. It was robust.
Why does this matter for quantum gravity?
Because quantum gravity theories suggest time might not be fundamental—it might emerge from quantum relationships. This experiment shows that's possible, at least in a controlled system.
So we might be living in a universe where time is emergent, not fundamental?
That's the long-term question. This is a proof of concept in a laboratory. But it suggests the framework is worth taking seriously.
What happens to our intuition about causality if time is emergent?
Causality doesn't disappear. The ordering still works. But it becomes relational—time emerges from the system's internal structure, not from outside it.