'Time was speeding up, slowing down, or even stopping': Physicist demonstrates a key theory of time by buil...

Key Points:

• Physicist Giovanni Barontini created a "mini-universe" using ultracold atoms to experimentally observe time emerging within an isolated quantum system, addressing the fundamental question of where time originates if the universe has nothing outside it.
• By splitting a Bose-Einstein condensate into two halves—a "bright sector" and a "dark sector"—and ignoring the dark half, Barontini demonstrated that time can arise internally based on entropy exchange between the two parts, with entropy flow defining an "entropic time" clock.
• The experiment showed that this internal time could speed up, slow down, or stop depending on the entropy exchange rate, matching but differing in flow from laboratory time, providing the first quantitative lab test of relational time theories in quantum cosmology.
• Barontini’s findings suggest both time and the arrow of time may emerge from an observer’s loss of information (ignorance) about part of the system, linking the flow of time to entropy and information theory.
• This research opens the door to simulating more complex cosmological phenomena, such as black hole analogues and early universe conditions, using similar ultracold atom setups in future experiments.