Physicists Explore if Time is a Quantum Illusion

New research suggests that the passage of time may not be a fundamental feature of the universe, but rather an illusion that emerges from quantum interactions between different systems [1]. By creating a "toy universe" using ultracold atoms, scientists have demonstrated how a sense of time can arise from quantum correlations, potentially offering a new perspective on the nature of reality [1].

Key takeaways

• Physicists define time by measuring changes in physical systems, such as the movement of clock hands or the shifting of electrons, rather than observing time directly [2].
• A recent experiment cooled 20,000 rubidium atoms to near absolute zero, dividing them into "bright" and "dark" sectors to observe how quantum interactions create an internal sense of time [1].
• The Page–Wootters theory proposes that dynamics emerge from entanglement between a system and a clock, a concept that remains unchanged over time [2].
• While these experiments provide a framework for understanding quantum correlations, experts note that they do not yet confirm how time functions at the scale of the entire universe [1].

Modeling a Timeless Cosmos

The concept of time as an emergent property has roots in the 1930s, when physicist Nevill Mott first suggested that time arises from quantum correlations [1]. This idea was further developed in 1983 by Don Page and Bill Wootters, who proposed that dynamics could be described through an entangled state between a system and a clock [2]. In this "timeless" view, the past, present, and future occur simultaneously, and the "flow" of time is merely a perception resulting from our correlation with the universe's state [2].

To test these theories, Giovanni Barontini at the University of Birmingham constructed a laboratory model using 20,000 rubidium atoms cooled to temperatures near absolute zero [1]. By using lasers to force interactions between "bright" and "dark" sectors of atoms, Barontini observed changes in the system's entropy [1]. Because time is associated with increasing disorder, this interaction allowed him to define an internal time for the toy universe [1]. Notably, the results matched calculations derived from the Schrödinger equation, marking the first time this equation has been successfully applied to such an internal time system [1].

Why it matters

This research connects to the broader challenge of unifying gravity and quantum theory, a goal that some physicists believe will eventually require a framework where time does not exist at the most fundamental level [1]. While some experts, such as Claus Kiefer, point out that laboratory toy models lack the complex interactions found in the actual universe, others like Carlo Rovelli suggest these experiments are valuable for exploring unknown physics [1]. Barontini plans to continue his research by using lasers to simulate regions similar to black holes, further testing whether these quantum models can provide insight into the nature of time across different scales [1].