Time as an Emergent Phenomenon
Does time truly exist as a fundamental dimension, or is it merely an illusion arising from quantum mechanics? A new experiment using a "toy universe" of ultracold atoms suggests the latter. Physicists at the University of Birmingham have demonstrated that time can emerge from quantum interactions between different parts of a system, rather than being a pre-existing backdrop. The findings, published in June 2026, add weight to the idea that time may not be a fundamental property of our universe but rather a consequence of quantum entanglement and entropy.
Building a Toy Universe
Giovanni Barontini, the lead researcher, was inspired while watching his 6-year-old son play with building blocks. He realized that physicists similarly construct small, controlled systems in the lab—like ultracold atom setups—that mimic aspects of the cosmos. However, these systems often remain static and unchanging, raising the question: if nothing happens, does time even exist? To explore this, Barontini and his team created a toy universe using about 20,000 rubidium atoms cooled to near absolute zero using lasers and electromagnetic fields.
Bright and Dark Sectors
The researchers divided the atoms into two sectors, labeled "bright" and "dark," in analogy to dark matter. Initially, this toy universe was timeless and unchanging—a static state with no apparent flow of time. The key step came when Barontini used lasers to coax the two sectors into exchanging atoms, thereby allowing them to interact on a quantum level. This interaction altered the entropy, or disorder, of the system. In our universe, time flows in the direction of increasing entropy, so by tracking entropy changes, the team could define an internal time for the toy universe.
Quantum Interactions Create Time
Once this internal time was established, Barontini could use it in the Schrödinger equation—the fundamental equation of quantum mechanics—to calculate the atoms' quantum states. The results matched the experimental observations, confirming that the emergent time was a valid parameter. This suggests that time can arise from quantum correlations and interactions, rather than being a given dimension.
Historical Precedents
The concept of time as an emergent property is not new. In atomic physics, physicist Nevill Mott first proposed the idea in the 1930s, and it has been explored theoretically ever since. However, experimental evidence remained elusive until 2013, when Marco Genovese at the National Metrology Institute of Italy and his colleagues demonstrated a similar effect using entangled particles of light. In that experiment, a sense of time also emerged from quantum correlations. Barontini's work extends these findings by using a more complex system of many atoms, bringing the idea closer to a realistic model of the universe.
Implications for Our Understanding of Reality
If time is indeed an illusion, it would revolutionize our understanding of physics and reality. The arrow of time—the one-way flow from past to future—is closely tied to entropy. In the toy universe, time only appeared when the two sectors interacted, increasing entropy. This mirrors the thermodynamic arrow of time in our universe, where entropy always increases. The experiment suggests that time may be a macroscopic phenomenon that emerges from the quantum behavior of many particles, rather than a fundamental aspect of spacetime.
Future Research Directions
The Birmingham team plans to explore more complex toy universes, perhaps with additional sectors or different types of interactions. They also aim to investigate whether time can emerge in systems without any initial asymmetry, which would further challenge the notion of time as fundamental. Such experiments could help bridge the gap between quantum mechanics and general relativity, where time plays very different roles.
Conclusion
While the toy universe is a simplified model, it provides compelling evidence that time may be a quantum illusion. The experiment shows that time can emerge from quantum interactions and entropy changes, supporting the view that time is not a fundamental property but a derived one. As physicists continue to probe the nature of reality, this work offers a tantalizing glimpse into a universe where time itself may be just another quantum phenomenon.
This article is based on reporting by New Scientist. Read the original article.
Originally published on newscientist.com