The curious case of the quantum arrow of time
The curious case of Benjamin Button tells the story of a man, played by Brad Pitt, who is born as an eighty-year old and grows younger as the years pass. The tale is obviously a fantasy — in reality, Brad Pitt is ageing. Angelina Jolie is ageing. You and I are ageing. As macroscopic objects, it’s inevitable, and no amount of surgery can turn back the clock. But just why time only marches in one direction has long been a mystery.
Physicist Jonathan Dowling believes that quantum mechanics may hold the answer. At first sight, it may seem obvious to think that the ageing process is written into the movement of molecules in our skin. But on the microscopic scale, this movement is time reversible. If you look at the equations that govern how molecules interact with each other, they work just as well backwards as forwards. In other words, on the microscale, it’s just as likely that shed skin particles should re-join our bodies as time passes, gradually making us look younger. Time’s arrow could run backwards or forwards.