For centuries, time has been one of the greatest mysteries in science. We experience it every day as seconds, minutes, and hours passing by. We remember the past, live in the present, and move toward the future. But what if time is not a fundamental part of the universe at all? What if time is something that emerges naturally from the way matter behaves?
A groundbreaking experiment by Professor Giovanni Barontini from the University of Birmingham has brought scientists one step closer to answering this profound question. By creating a tiny “mini-universe” inside a laboratory, researchers have demonstrated that time may not require a clock to exist. Instead, it can emerge from changes occurring within a system itself.
The findings, published in Physical Review Research, provide the first controlled experimental evidence that time can arise from internal processes rather than from an external ticking clock. This remarkable work could reshape our understanding of the universe, quantum mechanics, gravity, and even the origins of the cosmos.
The Mystery of Time
Most people think of time as a universal background that flows continuously. Clocks simply measure this flow. However, some of the deepest theories in modern physics suggest a very different picture.
One famous idea comes from the Wheeler–DeWitt equation, a theoretical framework that attempts to describe the entire universe using quantum mechanics. According to this theory, the universe may not contain a built-in concept of time at all.
Instead, the universe exists as a single quantum state where everything is connected. In this picture, there is no external clock standing outside the universe counting seconds. If time exists, it must somehow emerge from the relationships between objects inside the universe.
This creates a major challenge for physicists. If there is no fundamental clock, how do events happen in order? How do we know what comes before and what comes after?
Professor Barontini’s experiment was designed to explore exactly this question.
Building a Mini-Universe
To investigate the nature of time, researchers created a miniature quantum universe in the laboratory.
The experiment used approximately 24,000 ultracold atoms cooled to temperatures only a few billionths of a degree above absolute zero. At such incredibly low temperatures, quantum effects become dominant, allowing scientists to study fundamental physical principles in a controlled environment.
The atoms were trapped inside a sealed quantum system and divided into two separate regions using a thin barrier created by laser beams.
One region was called the “bright” sector because it could be observed directly. The other was known as the “dark” sector because it remained hidden from observation.
Together, these regions formed a simplified model of a tiny universe that was isolated from the outside world.
A Tiny Cosmos with a Big Bang and Big Crunch
One of the most fascinating aspects of the experiment was the behavior of the bright region.
The bright sector repeatedly expanded and contracted, mimicking a miniature version of cosmic evolution. Scientists compared this cycle to a Big Bang followed by a Big Crunch.
The Big Bang is the event that started our universe roughly 13.8 billion years ago. A Big Crunch, on the other hand, is a hypothetical future scenario in which the universe stops expanding and eventually collapses back into itself.
Inside the mini-universe, the bright region experienced repeated cycles similar to these cosmic events. Yet researchers were able to reconstruct the sequence of events without referring to any external laboratory clock.
This was a crucial breakthrough.
The system itself provided all the information needed to determine the order of events.
Time Without a Clock
Normally, scientists measure time using clocks. Every experiment relies on some external device that tracks the passage of seconds.
Barontini’s experiment challenged this assumption.
The results showed that time could be defined entirely by changes occurring inside the quantum system. No outside clock was required.
Instead of measuring time using ticking seconds, researchers measured it using changes in the arrangement of atoms.
As atoms moved between the bright and dark regions, the distribution of particles changed. These changes created a natural way to track the progression of events.
In other words, time emerged from the evolution of the system itself.
The Role of Entropy
The key concept behind this discovery is entropy.
Entropy is often described as a measure of disorder or the spread of energy and matter within a system. It plays a central role in thermodynamics and is closely linked to the familiar arrow of time.
For example, a dropped glass shatters into pieces, but the pieces do not spontaneously reassemble themselves. Entropy increases, creating a preferred direction from past to future.
In the mini-universe, entropy became the foundation of time itself.
As atoms moved between the bright and dark sectors, the spread of particles changed. Whenever this distribution increased or decreased, the system experienced the passage of time.
When the distribution remained unchanged, time effectively stopped.
Professor Barontini referred to this phenomenon as “entropic time.”
A New Arrow of Time
The experiment revealed several remarkable properties of entropic time.
First, it flowed consistently in one direction, creating a clear arrow of time similar to what we experience in everyday life.
Second, it correctly ordered events even while the mini-universe expanded and contracted.
Third, the rate of time could change. Depending on how entropy moved through the system, time could speed up or slow down.
These properties closely resemble many features of time in the real universe.
The results suggest that the flow of time may emerge naturally from changes in entropy rather than existing as a separate fundamental ingredient of reality.
Connecting to Quantum Mechanics
Another major achievement of the study was showing that entropic time can be used within the mathematical framework of quantum mechanics.
Researchers demonstrated that a version of the Schrödinger equation—the central equation of quantum physics—can still be written using entropic time.
This means scientists can predict how a quantum system evolves even when conventional clock-based time is removed.
The finding is important because it suggests that physics can remain fully predictive even if time emerges from internal changes rather than existing independently.
Why This Matters
The implications of this research are enormous.
For decades, questions about time have largely remained in the realm of theoretical physics. Many ideas about quantum gravity, the Big Bang, and the structure of the universe have been impossible to test directly.
This experiment changes that.
By creating a laboratory system that mimics aspects of the universe, scientists now have a powerful platform for exploring deep cosmological questions experimentally.
Researchers can investigate how time emerges, how quantum systems evolve without clocks, and how the early universe may have behaved shortly after the Big Bang.
Looking Toward the Future
The current mini-universe is relatively simple, but future versions could become much more sophisticated.
Scientists hope to build larger and more complex quantum systems capable of simulating phenomena that were previously inaccessible.
These systems may help researchers study the physics of the Big Bang, explore hypothetical Big Crunch scenarios, and even simulate certain aspects of black holes in the laboratory.
Such experiments could provide valuable clues about quantum gravity—the long-sought theory that would unite quantum mechanics with Einstein’s theory of gravity.
A New Understanding of Reality
Professor Barontini’s mini-universe offers an exciting glimpse into one of science’s deepest mysteries.
The experiment suggests that time may not be a fundamental ingredient of reality. Instead, it could emerge naturally from the changing relationships between particles and the flow of entropy within a system.
While many questions remain unanswered, this research provides the strongest experimental evidence yet that time can arise without a clock.
By transforming a philosophical puzzle into a laboratory experiment, scientists have opened a new path toward understanding the true nature of time—and perhaps the universe itself.
Reference: Giovanni Barontini, Testing the problem of time with cold atoms, Physical Review Research (2026). DOI: 10.1103/1h9j-df4k
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