It’s easy to take time’s arrow for granted — but the gears of physics actually work just as smoothly in reverse. Maybe that time machine is possible after all?

An experiment from 2019 shows just how much wiggle room we can expect when it comes to distinguishing the past from the future, at least on a quantum scale. It might not allow us to relive the 1960s, but it could help us better understand why not.

Researchers from Russia and the US teamed up to find a way to break, or at least bend, one of physics’ most fundamental laws of energy.