A researcher at the University of Birmingham conducted an experiment using approximately 24,000 ultracold atoms to investigate whether time could emerge from changes within a system rather than existing as a fundamental feature of reality. The work, published in Physical Review Research, explores a theoretical possibility suggested by equations combining quantum mechanics with gravity, such as the Wheeler-DeWitt equation, which describe the universe without an external time variable.
The experimental setup involved confining atoms at temperatures near absolute zero and using two laser beams to create a divided quantum system with an observed region and an unobserved region. The atoms could move between these sections while the observed region underwent cycles of expansion and contraction. Rather than relying on conventional timekeeping, the researcher tracked progression through changes in particle distribution and entropy—the spread and disorder of particles within the bright region. This approach allowed the system’s evolution to be measured and events to be sequenced without reference to an external clock.
The framework developed from this work, termed “entropic time,” demonstrated several significant properties. It consistently moved in one direction, establishing what physicists refer to as the arrow of time that distinguishes past from future. The system could correctly order events even as the miniature universe expanded and contracted, and the rate of progression could vary depending on how entropy changed within the system. Notably, the researcher showed that the Schrödinger equation, a foundation of quantum mechanics, could be reformulated using entropic time as the basis for describing system dynamics.
The findings address a fundamental puzzle in physics: if the universe operates according to basic laws that function identically whether time moves forward or backward, why do we experience time flowing in only one direction? The research suggests that time’s apparent direction and passage may arise from the relationships and transformations occurring within the universe itself rather than existing as an independent, pre-existing dimension.
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