Time Might Just Be an Illusion, New Quantum Experiment Suggests

Time may not be a fundamental feature of the universe at all, according to a new lab experiment by physicist Giovanni Barontini of the University of Birmingham, published June 11 in Physical Review Research. Instead, it appears to be an illusion that emerges from the internal interactions and disorder of matter.

The question dates back to the Wheeler-DeWitt equation, a key equation in quantum gravity that describes the universe as a whole system with no external time parameter — there’s no cosmic clock ticking away outside it. Barontini set out to test whether time instead arises from how things inside the universe interact with each other.

To do this, he built a mini-universe in his lab using a Bose-Einstein condensate, a state of matter that forms only near absolute zero, cooling around 24,000 atoms until they moved as a single quantum ‘super particle.’ He trapped the condensate, split it with a thin sheet of laser light, and watched only one half — the ‘bright sector’ — while deliberately not observing the other.

The atoms flowed back and forth across the divide, occasionally spilling over completely; Barontini called those moments the ‘Big Bang’ and ‘Big Crunch.’ Rather than use an external clock, he built an ‘entropic time’ from the disorder flowing between the two halves, and it alone was enough to correctly order the sequence of events.

Time sped up, slowed down, and stopped entirely depending on how the atoms moved. ‘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 both time’s existence and its forward direction trace back to the same source: an observer’s choice to ignore part of a system, with that ignorance — measured as entropy — generating the flow of time in the part being observed.