Rewriting the Rules of Time
What if time wasn't a universal constant, but something that simply… emerges? A revolutionary experiment at the University of Birmingham, led by Professor Giovanni Barontini, is challenging our fundamental understanding of time, offering the first experimental evidence that time can arise from within a system itself, rather than being an external, independent clock.
Published in Physical Review Research, the study details the creation of a 'mini-universe' – a hermetically sealed quantum system comprising 24,000 ultracold rubidium atoms, just a few billionths of a degree above absolute zero. This miniature cosmos, divided into 'bright' and 'dark' regions, undergoes cycles akin to a Big Bang and Big Crunch. Crucially, the sequence of events is reconstructed from within the system, without any reference to an outside clock.
The Birth of 'Entropic Time'
The key insight comes from what Professor Barontini terms 'entropic time.' The team observed that as atoms shifted between regions, causing the spread or disorder (entropy) within the 'bright' sector to change, the system effectively 'moved forward in time.' When the atomic distribution remained static, time essentially stopped. This 'entropic time' consistently flows in one direction, orders events, and even accelerates or decelerates based on entropy changes.
This remarkable finding offers a powerful new lens through which to view complex theories like quantum gravity, where time often doesn't appear as a built-in feature. The 'mini-universe' provides a unique test bed for probing the very nature of time, allowing scientists to experimentally investigate questions about the universe's origins and black holes that were once confined to theoretical discussions.
