Physicists Built a Tiny Universe in a Lab and Watched Time Create Itself

Physicist Giovanni Barontini, at the University of Birmingham, set out to answer one of the oldest puzzles in physics: where does time actually come from? His answer, published on June 11 in the journal Physical Review Research, suggests time isn’t a built-in feature of reality at all — it emerges from how things inside a system interact.

The puzzle traces back to the Wheeler-DeWitt equation, a central equation in quantum gravity, the field trying to unify Einstein’s theory of gravity with quantum mechanics. That equation describes the universe as a whole system with no external time parameter — there’s no cosmic clock ticking away outside it. So Barontini hypothesised that time might instead be a result of how things behave from the inside.

To test the idea, he built his own mini-universe inside a lab using a Bose-Einstein condensate, a state of matter that only forms near absolute zero, where roughly 24,000 individual atoms slow to a near standstill and behave as a single quantum ‘super particle.’ He trapped the condensate and split it down the middle with a thin sheet of laser light, observing only one half — the ‘bright sector’ — while deliberately ignoring the other.

Atoms naturally flowed back and forth across the barrier, occasionally spilling over entirely; Barontini called the moment they flooded the bright region the ‘Big Bang,’ and the moment they flowed back out the ‘Big Crunch.’ Rather than using an external clock, he built an ‘entropic time’ — a measure of disorder flowing between the two halves — and used it to perfectly order the sequence of events from inside the system alone.

The effect was striking: time sped up when atoms moved rapidly across the barrier, slowed as the flow slowed, and stopped entirely when the atoms stood still. ‘Time was speeding up or slowing down, or even stopping, depending on what the system was doing,’ Barontini told Live Science. He also found that time’s one-way forward direction stems from the same source as its existence — an observer’s choice to ignore information about the unobserved half, with that ignorance, measured as entropy, creating the flow of time in the observable half.