What is time, and does it truly exist beyond our perception? A physicist from the University of Birmingham has taken a significant step toward solving this fundamental scientific mystery. Professor Giovanni Barontini created a quantum miniature universe in the laboratory. The experiment demonstrated that no external clock is needed to measure or establish the passage of time. His research, published in the journal Physical Review Research, shows that time may be a by-product of the behavior of quantum systems rather than a fundamental component of the cosmos.
In modern theoretical physics, particularly quantum gravity, the idea that time is not a fundamental background against which events unfold is becoming increasingly widespread. For example, the famous Wheeler–DeWitt equation describes the Universe as a single static quantum state with no built-in timer.
The everyday movement from the past to the future that we call time must arise from complex relationships among particles within a system. The principal challenge was determining how this hypothesis could be tested experimentally.
A Laboratory Recipe for the Cosmos
To put the theory into practice, Professor Barontini constructed a simplified quantum model of the Universe. He used a cloud of 24,000 atoms cooled to within only a few billionths of a degree above absolute zero.
The atoms were isolated within a closed system and separated by a thin optical barrier formed by two laser beams operating at different frequencies. This created two regions: an observable “bright” sector and a hidden “dark” sector.
Within this microcosm, the “bright” region alternately expanded and contracted. This resembled a cyclic model of our Universe, extending from the Big Bang to the Big Crunch. Because the system was completely isolated, the scientists could record the sequence of events solely through the internal processes of the miniature universe, without relying on any external instruments.
The Birth of “Entropic Time”
The experiment showed that a form of “time” emerged within the quantum system through changes in the level of disorder, or entropy, as atoms migrated between the bright and dark regions. As long as the particles moved and redistributed themselves, the system evolved—in other words, it moved forward in time. Once this movement subsided and the distribution of particles became constant, time within the miniature universe literally stopped.
Barontini called this phenomenon “entropic time.” It has several distinctive properties:
- it always moves in one direction, creating a clear “arrow of time”;
- it logically orders events even during the contraction and expansion of the quantum cloud;
- it can accelerate or slow down depending on the rate at which entropy changes.
A Bridge to Quantum Gravity
The researchers also succeeded in adapting the fundamental equation of quantum mechanics—the Schrödinger equation—to this “entropic time.” This means that physicists can successfully predict the behavior of quantum systems even in the absence of classical time measured by clocks.
This approach addresses a long-standing problem: how to order events in a Universe that has no built-in timer. Scientists now have a real laboratory instrument instead of purely mathematical models. In the future, they plan to use similar microsystems to model the physics of black holes, the first moments after the Big Bang, and to test competing theories concerning the origin of our Universe.
Previously, we attempted to determine whether time flowed differently immediately after the Big Bang.
According to sciencedaily.com
