![\"\"](\"https:\/\/www.europesays.com\/ie\/wp-content\/uploads\/2026\/06\/Low-Res_090526_mini_universe-3.jpg\" "\\"Scientists")
<\/a>Experiment to trap and cool rubidium atoms close to absolute zero. Credit \u2013 University of Birmingham<\/p>\nThe researchers confined the particles inside an isolated quantum system. They then used two laser beams to form a thin barrier that divided the setup into two regions. One region remained observable, or \u201cbright.\u201d The other stayed hidden from direct observation and became the \u201cdark\u201d sector.<\/p>\n
Inside this simplified cosmos, the bright region repeatedly expanded and contracted. The cycle resembled theoretical versions of a Big Bang followed by a Big Crunch, a scenario in which the universe\u2019s expansion eventually reverses.<\/p>\n
Because the system remained sealed from its surroundings, scientists reconstructed the sequence of events using only changes occurring within the mini-universe. They did not need an external laboratory clock.<\/p>\n
Time through disorder<\/p>\n
The experiment points to a concept known as \u201centropic time.\u201d Rather than treating time as an independent backdrop to reality, the researchers linked its passage to changes in entropy, or the way particles spread through the system. Atoms moved between the bright and dark regions, altering the distribution of matter.<\/p>\n
As those distributions evolved, the system moved forward in time. When the arrangement stopped changing, time effectively stood still. The team found that this version of time<\/a> flowed in a consistent direction. It also correctly ordered events, even during repeated cycles of expansion and contraction. Its pace could speed up or slow down depending on how entropy shifted within the system.<\/p>\n \u201cIn some theories of the universe, especially quantum gravity, time doesn\u2019t appear as a built-in feature,\u201d Barontini said. \u201cYet in everyday life, time flows from past to future. Why is this so, when most basic laws of physics work the same way forwards and backwards?\u201d<\/p>\n Bringing cosmology to the lab<\/p>\n Barontini said the study provides controlled experimental evidence that changes within a system can define time without relying on an external clock. \u201cIt offers new insight into the nature of time in quantum<\/a> gravity,\u201d he said. \u201cIt could be used to describe dynamics just as effectively as conventional time.\u201d<\/p>\n The researchers also showed that quantum mechanics remains mathematically consistent under this framework. They rewrote a version of the Schr\u00f6dinger equation using entropic time, allowing predictions about how a quantum probability distribution evolves.<\/p>\n The work addresses a long-standing puzzle in physics: If the universe has no fundamental clock, how can events be arranged into a meaningful sequence of \u201cbefore\u201d and \u201cafter\u201d? Perhaps more importantly, the experiment transforms abstract debates into testable science.<\/p>\n