Set your alarm clock

Physicists are not sure what time is or how it works. The dominant position is the one articulated recently by Carlo Rovelli, who reminds us that the equations of general relativity – one of the best-tested scientific theories of all time – are time-invariant, meaning that time is just one more dimension of spacetime, and it doesn’t ‘flow’ in the way most of us think it does.

Rovelli offers the scientific take about several common misconceptions about time: (i) it doesn’t tick uniformly everywhere in the universe, as clocks travelling faster give slower measures of time, a relativistic effect due to gravity; (ii) the concept of ‘now’ is also a bit shaky, scientifically, as everything we