The nature of time may be nothing more than an illusion generated through quantum interactions within the universe. This intriguing concept arises from innovative space toy models, potentially offering insights into the true essence of time in our cosmos.

Giovanni Barontini, while studying at the University of Birmingham in England, contemplated the nature of time as he observed his six-year-old son’s imaginative play. “He was constructing his own microcosms; it struck me that this mirrors our work in the lab with ultracold atomic systems,” he reflects. “However, I began to ponder that this universe could be perceived as rather dull, as inactivity implies no passage of time.”

To delve into whether time is genuinely an illusion within these systems, Barontini employed lasers and electromagnetic forces to cool approximately 20,000 rubidium atoms to temperatures near absolute zero. He divided these atoms into two sectors, likening one to ‘dark matter’, labeling one region as “bright” and the other as “dark”.

Despite this initial state of timelessness, Barontini directed lasers to facilitate atomic exchanges and interactions at a quantum level, thereby modifying the entropy or disorder of this universe—asserting that the flow of time correlates with increasing entropy. He successfully defined an internal concept of time for this toy universe, employing the Schrödinger equation to calculate the quantum state of atoms, which aligned with the experimental findings.

This idea that time is not an inherent feature but results from quantum correlations was initially proposed by physicist Neville Mott in the 1930s, and it has since been the subject of theoretical exploration. It wasn’t until 2013 that Dr. Marco Genovese and his team at the Italian National Institute of Metrology first demonstrated its feasibility through experiments involving entangled light particles, further establishing the concept that the essence of time emerges from quantum correlations.

“This study builds on previous concepts and brings notable advancements,” comments Genovese. Notably, the cold-atom universe exhibits greater complexity than previous light-based models. Barontini innovatively applied the Schrödinger equation within the internal framework of this system, a feat previously unachievable.

Klaus Kiefer from the University of Cologne suggests that this experimental paradigm links to broader questions surrounding the unification of gravitational and quantum theories into a comprehensive framework applicable across all scales of the universe. While this inquiry persists, some physicists propose that such a comprehensive theory might fundamentally lack a predetermined notion of time. Kiefer notes substantial differences—such as the limited interactions between ultracold atoms transitioning between sectors compared to complexities in the actual universe.

In contrast, Carlo Rovelli from the University of Aix-Marseille cautions that such experiments may not unveil new insights about time, as they largely rely on established physics. Nevertheless, approaching them as analogs to significant unsolved issues might inspire innovative treatments of uncharted physics, akin to the enduring conundrum of quantum gravity.

Barontini regards this study as empirical support for long-standing hypotheses, underscoring their acceptance within the scientific community, although he concedes that it does not elucidate the mechanisms of time across various scales.

As Barontini continues to explore this intriguing frozen miniverse, he intends to use lasers to create a confined area, echoing the gravitational dynamics of a black hole—raising further questions about the nature of time and space.