Science & Tech · Science & Environment · 7 hrs ago
Ultracold atoms demonstrate a way to measure time without an external clock
A physicist at the University of Birmingham in the UK used about 24,000 ultracold atoms to create a miniature quantum system.
The atoms were arranged in two regions and cycled through patterns of expansion and contraction, but the experiment did not recreate the real universe.
Instead of using an outside clock, the team tracked changes in the atoms’ distribution between the regions.
Those changes provided an internal measure called entropic time, which advanced when the distribution changed and stopped advancing when it did not.
The experiment showed that this measure could give events an order and describe how the system evolved.
The results offer a way to test ideas about time’s nature, including whether time may emerge from changes within a system rather than exist as an independent feature.
The findings were published in Physical Review Research.
A University of Birmingham physicist demonstrated a way to measure time through changes within a quantum system, without an external clock.
Giovanni Barontini used about 24,000 ultracold atoms in an isolated system.
The atoms moved between two regions, and changes in their distribution provided an internal measure called entropic time.
The observed region went through repeated cycles of expansion and contraction, which were simplified analogies to the Big Bang and a hypothetical Big Crunch.
The experiment investigated whether time might emerge from changes within a system rather than exist as a fundamental property.
- Who
- Giovanni Barontini, a physicist and professor at the University of Birmingham.
- What
- He demonstrated an internal way to measure time in a quantum system, without relying on an external clock.
- When
- The results were published on November 2, 2026.
- Where
- The University of Birmingham in the United Kingdom.
- Why
- To investigate whether time is fundamental or can emerge from changes within a system.
This story does not have two clearly opposing sides.
About 24,000 ultracold atoms were confined in an isolated quantum system divided into bright and dark regions.
The bright region underwent repeated cycles of expansion and contraction as atoms shifted between the regions.
The results were published in Physical Review Research.
- Atom count
- About 24,000
- Researcher
- Giovanni Barontini
- Institution
- University of Birmingham, United Kingdom
- Internal time measure
- Entropic time
- Publication
- Physical Review Research, November 2, 2026