How One Scientist Made A Mini Universe To Prove We're Wrong About Time

Most people agree that outside of science-fiction movies, time moves forward constantly. As such, determining how much time has passed since a given event is typically as simple as checking a clock. But what if clocks had never been invented — would it still be possible to find out when (and in what order) different things had happened? According to Giovanni Barontini, a scientist from the University of Birmingham, this isn't just possible, it's the reality we live in.

To prove the hypothesis, Barontini created a "miniature universe" composed of roughly 24,000 rubidium atoms, chilled almost all the way down to absolute zero so that they acted as more of a collective cloud than individual particles. These were enclosed in an inescapable trap, which was split in half by a specially-configured laser. One side (the "bright" side) was observed while the other (the "dark" side) was not. In this experiment, the bright side's changing entropy was used to track time, meaning the internal timer only progressed as atoms crossed the laser barrier.

By measuring the way the cloud expanded and contracted, as well as the exchange of atoms, it became possible to reveal the order in which events happened. However, because it's possible for time to effectively stop (when there is no atomic exchange between sides), the recorded internal clock disagreed with the external clock as to when exactly events occurred.

Essentially, this experiment shows that in a controlled environment, it's possible to measure the flow of time simply by measuring entropy changes in an atomic system. This is hugely important because the two models underpinning our current understanding of physics, Einstein's theory of general relativity and quantum mechanics, don't always agree on what time is or how it works. For instance, in certain situations, it's possible to reverse time in specific quantum systems. This experiment, therefore, is a step toward unifying these two theories and learning why events occurring at a planetary scale don't always happen the same way in quantum environments.

It's important to recognize that this is just the starting point for further experimentation. After all, it doesn't simulate various factors that could impact the flow of atoms, such as black holes, and there are many other variables that could be changed including trap shape, atomic density, and the height of the laser barrier. The cloud's repeated oscillation between the dark and bright sides could also help scientists simulate conditions immediately following the Big Bang, and potentially even the lead-up to the Big Crunch, when the universe theoretically collapses into itself. This experiment's true impact on physics likely won't be apparent for a while, but at least now there are several ways to track exactly how long it takes.