Physicists at the University of Birmingham have successfully created a laboratory “mini universe” that challenges the traditional necessity of an external clock to measure time. By observing a system of 24,000 ultracold atoms, Professor Giovanni Barontini demonstrated that time can emerge naturally from the internal entropy and disorder of a quantum system, according to a study published in Physical Review Research.
Experimental Evidence for Entropic Time
To test whether time is a fundamental property or an emergent one, Professor Barontini and his team constructed a highly isolated quantum system. They cooled 24,000 atoms to temperatures just a few billionths of a degree above absolute zero. By using two laser beams of varying frequencies to create a physical barrier, the researchers split the cloud into two distinct zones: a “bright” region and a “dark” region.
The system functioned as a self-contained universe. The bright region underwent cycles of expansion and contraction, mimicking the hypothetical “Big Bang” and “Big Crunch” scenarios. Crucially, the researchers were able to reconstruct the sequence of events within this system without reference to any external laboratory clocks. This suggests that “time” is not necessarily a universal background constant but can be a byproduct of how entropy—the measure of disorder—redistributes within a closed quantum system.
In this experiment, “entropic time” functioned as a reliable arrow of time, flowing consistently in one direction. It allowed the researchers to correctly order events even as the “mini universe” changed size, proving that internal dynamics can replace the need for an external ticking clock.
Implications for Quantum Gravity
This research addresses a long-standing tension in physics: the apparent contradiction between our experience of time and the mathematical foundations of quantum gravity. Many theories of quantum gravity suggest that time is not a built-in feature of the universe. However, because our daily experience involves a clear flow from past to future, reconciling this with the reversible nature of most fundamental physical laws remains a challenge.
According to Professor Barontini, this experiment provides the first controlled evidence that time can be defined by internal system changes. The team found that the Schrödinger equation—the bedrock of quantum mechanics—remains predictive even when time is defined by internal entropy rather than a standard clock. This validation suggests that scientists may be able to model complex quantum dynamics without relying on the assumption of an absolute, external timeframe.
Future Research and Simulated Universes
The methodology established at the University of Birmingham offers a new framework for exploring extreme cosmic phenomena in a laboratory setting. By scaling these quantum systems, researchers aim to simulate more complex environments, including black holes and the early stages of the Big Bang.
This approach transforms abstract theoretical concepts into testable laboratory data. As researchers refine these “mini universes,” they hope to uncover whether competing theories of time can be verified or discarded through direct observation. This provides a tangible path forward for physicists attempting to describe the evolution of the universe from the inside out.
Frequently Asked Questions
- What is “entropic time”? It is a concept where time emerges from changes in the disorder or entropy of a system, rather than existing as an independent, external background.
- Why is this experiment significant? It provides the first controlled evidence that events can be ordered and measured within a system using only internal changes, potentially resolving issues in quantum gravity theories.
- Does this mean time isn’t real? The study does not argue that time is unreal, but rather that it may be an emergent property of quantum dynamics rather than a fundamental “ticking clock” built into the fabric of reality.
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