Physicists created a tiny universe and watched time emerge without a clock

What if time is not a fundamental part of the universe, but something that emerges from the changes taking place inside it? A physicist at the University of Birmingham has created a miniature universe in the laboratory that offers a surprising new way to investigate this possibility. Using thousands of atoms cooled to temperatures barely above absolute zero, Professor Giovanni Barontini demonstrated that the passage of time can be measured without relying on an external clock.

Instead, a form of time emerges naturally from the behavior of particles within the experimental system. The findings, published in Physical Review Research, provide experimental evidence for an intriguing idea in theoretical physics: Time may not be an essential ingredient of reality. It could arise from the relationships and changes occurring within the universe itself.

Why Some Physicists Think Time May Not Be Fundamental We usually think of time as something that continuously moves forward, regardless of what happens around us. Seconds pass, planets orbit stars, and the universe evolves. But some theories of physics suggest that time may work very differently at the most fundamental level.

One example is the Wheeler-DeWitt equation, which appears in attempts to combine quantum mechanics with gravity. In this framework, the universe can be described as a single, unchanging quantum state, with no external clock marking the passage of time. Quantum particles can exhibit both wave-like and particle-like properties, but the universe as a whole does not necessarily have a built-in time variable.

This creates a major puzzle. If the universe has no external clock, how can anything happen in a particular order? What determines which events come first and which happen later?

One possibility is that time emerges from the changing relationships between different parts of the universe. Barontini designed an experiment to investigate whether such a process could be observed in the laboratory. Creating a Miniature Universe With 24,000 Atoms To build his miniature cosmos, Barontini used a cloud of approximately 24,000 atoms cooled to just a few billionths of a degree above absolute zero.