For centuries, scientists and philosophers have wrestled with one of the deepest questions in physics: What is time? We measure it with clocks, organise our lives around it, and experience it as something that constantly moves forward. But what if time is not a fundamental feature of the universe at all?
A new experiment suggests that this may be the case. In a study published on June 11 in Physical Review Research, physicist Giovanni Barontini of the University of Birmingham demonstrated that a sense of time can emerge naturally within an isolated quantum system, without relying on any external clock.
The findings offer experimental support for a long-standing theoretical idea that time is not built into the universe itself but instead arises from interactions between matter and the information available to an observer. While the experiment does not rewrite the laws of physics overnight, it provides one of the clearest laboratory demonstrations yet of how time could emerge from within a closed system.
Why is the origin of time such a difficult question?
Modern physics describes time in two very different ways.
Einstein’s theory of general relativity treats time as part of spacetime, intertwined with the three dimensions of space. Gravity can stretch or compress time, which has been confirmed through experiments and even affects the accuracy of GPS satellites.
Quantum physics, however, tells a different story. Some of the equations that attempt to describe the entire universe do not contain time in the way we experience it. Instead, they suggest the universe could be fundamentally static.
This contradiction is known as the “problem of time.” If the universe has no outside observer and no external clock, where does the flow of time come from?
One possible answer is that time is an emergent property. Like temperature—which arises from the motion of countless atoms rather than existing on its own—time may emerge from relationships between different parts of a system.
Barontini’s experiment was designed to test that possibility.
How the physicist built a miniature universe
To explore the origins of time, Barontini created what is effectively a tiny quantum universe inside a laboratory.
The experiment relied on a Bose-Einstein condensate, an unusual state of matter that forms only when atoms are cooled to temperatures extremely close to absolute zero.
At these temperatures:
- Thousands of atoms move almost in unison.
- They behave collectively as one quantum object rather than as individual particles.
- Scientists can observe quantum behaviour on a much larger scale than usual.
This made the condensate an ideal environment for testing whether time could emerge naturally from internal interactions.
Splitting the quantum system
The condensate was trapped inside a controlled chamber and divided into two regions using a thin sheet of laser light.
Barontini observed only one half of the system, which he referred to as the “bright sector.” The other half was intentionally left unobserved.
Atoms naturally flowed back and forth across the laser barrier separating the two regions.
When a large number of atoms entered the bright sector, Barontini described it as a miniature “Big Bang.” As they later flowed back out, the system experienced what he called a “Big Crunch.”
These labels are analogies rather than literal recreations of cosmic events, but they helped researchers visualize how the system evolved over time.
Measuring time without a clock
Perhaps the most remarkable aspect of the experiment is that researchers deliberately avoided using any external clock to track what was happening.
Instead, they developed an internal measure called “entropic time.”
Entropy is commonly described as a measure of disorder or the number of possible arrangements within a system. It plays a central role in thermodynamics and is often associated with the direction in which time appears to move.
Rather than measuring seconds or minutes, Barontini tracked changes in entropy as atoms moved between the two halves of the condensate.
These changes allowed the researchers to determine the exact sequence of events occurring inside the isolated system.
In other words, the quantum system generated its own timeline.
The experiment suggests that time does not necessarily need an external reference point. It can arise from changes taking place within the system itself.
Why time sped up, slowed down, and even stopped
One of the study’s most intriguing observations was that the pace of time was not constant.
Instead, it depended entirely on how atoms moved through the system.
Researchers observed three distinct behaviours:
- Time appeared to speed up when atoms rapidly crossed the barrier.
- Time slowed as atomic movement became less active.
- Time effectively stopped when the atoms became completely stationary.
Speaking to Live Science, Barontini explained that the flow of time depended entirely on the internal dynamics of the system.
This does not mean clocks in everyday life would suddenly stop if atoms stopped moving. Rather, within this isolated quantum universe, the internal measure of time only advanced when physical changes occurred.
The findings reinforce an idea familiar in physics: change is closely tied to the passage of time.
What does entropy have to do with time?
The experiment also highlights an intriguing relationship between time and information.
Barontini intentionally chose not to observe one-half of the condensate.
That missing information introduced uncertainty into the system.
In physics, uncertainty and missing information are directly connected to entropy.
The researchers found that this increase in entropy naturally created a direction for time to move.
This means that the familiar “arrow of time”—our experience that time always moves from past to future—may emerge because observers never possess complete information about the systems they are studying.
Rather than existing as a built-in law of nature, the direction of time could arise from what is known and what remains hidden.
Does this prove time is an illusion?
Not quite.
The study provides compelling experimental evidence that a sense of time can emerge within an isolated quantum system, but it does not prove that time itself is an illusion throughout the entire universe.
Several important limitations remain.
First, the experiment involved an extremely small laboratory system operating under highly controlled quantum conditions.
Second, scientists do not yet know whether the same principles apply to galaxies, black holes, or the universe as a whole.
Finally, the findings represent one experimental demonstration among several competing ideas about the nature of time.
Future experiments will be needed to determine whether similar behaviour appears in other quantum systems or under different physical conditions.
Why this experiment matters
Despite its limitations, the research marks an important milestone.
For decades, many ideas about emergent time existed mainly as mathematical models. Barontini’s work provides an experimental platform for testing those theories in the laboratory.
The study could have implications for several areas of modern physics, including:
- Quantum gravity
- Cosmology and the early universe
- Black hole physics
- Quantum information science
- The relationship between entropy and the arrow of time
By demonstrating that an isolated system can organise its own sequence of events without an external clock, the experiment brings physicists one step closer to understanding one of science’s oldest mysteries.
Rather than viewing time as a universal backdrop against which everything happens, researchers may increasingly see it as something that emerges from the interactions, motion, and information contained within physical systems.
Whether that picture ultimately describes our universe remains an open question—but this miniature quantum universe has provided an intriguing glimpse of how time itself might come into existence.
