A ball in mid-bounce has its past and future trajectories determined by the laws of physics, but time will only flow into the future for us. While Newton’s laws of motion are the same whether you run the clock forwards or backwards in time, not all of the rules of physics behave identically if you run the clock forwards or backwards. (Credit: MichaelMaggs Edit by Richard Bartz/Wikimedia Commons)

No, the laws of physics are not time-symmetric

Whether you run the clock forwards or backwards, most of us expect the laws of physics to be the same. A 2012 experiment showed otherwise.

No matter when, where, or what you are in the Universe, you experience time in only one direction: forwards. In our everyday experiences, clocks never run…