New research from the University of Birmingham suggests that the fundamental nature of time may be more complex than previously understood, potentially emerging from quantum interactions rather than existing as a default dimension. The study, led by Giovanni Barontini, involved creating a 'toy universe' using ultracold rubidium atoms.
Barontini and his team cooled approximately 20,000 rubidium atoms to temperatures near absolute zero using lasers and electromagnetic forces. These atoms were then divided into two distinct sectors, analogous to dark matter, creating a miniature, initially unchanging universe. This static environment served as a baseline before quantum interactions were introduced.
The crucial step involved using lasers to encourage the two sectors of atoms to exchange particles, thereby initiating quantum-level interactions. This process led to a change in the 'entropy' – or disorder – of the toy universe. As time in our own universe is known to flow in the direction of increasing entropy, the researchers were able to define an internal sense of time within their experimental system. Significantly, this newly defined internal time could then be used within the Schrödinger equation, which describes how quantum systems evolve, to accurately calculate the atoms' quantum states, a feat not achieved in this context before.
This experimental evidence supports a long-standing theoretical concept, first proposed by physicist Nevill Mott in the 1930s, that time might arise from quantum correlations or interactions. While previous research in 2013 by Marco Genovese at the National Metrology Institute of Italy provided initial proof of feasibility using entangled particles of light, the Birmingham study's use of a more complex cold-atom universe represents a significant advancement. Genovese himself noted that the current work 'further elaborates on this idea with some significant progress'.
The findings could have implications for theoretical physics, particularly in the ongoing challenge of unifying gravity and quantum theory into a single framework. Some physicists speculate that such a unified theory might lack time at its most fundamental level. While the experiment mimics this situation, Claus Kiefer from the University of Cologne, Germany, cautions that differences exist, such as the simpler interactions between atoms in the toy universe compared to a larger cosmos. Barontini acknowledges that cosmologists might have objections to the work, but sees it as an experimental confirmation of long-held ideas, demonstrating their continued relevance.