“Sooner or later
the exact measurement of our time
and we’ll be on the ship that’s bound
for the bitterest shore. (II, 9)
Time is a mystery that does not cease to puzzle us. Philosophers, artists and poets have long explored its meaning while scientists have found that its structure is different from the simple intuition we have of it. From Boltzmann to quantum theory, from Einstein to loop quantum gravity, our understanding of time has been undergoing radical transformations. Time flows at a different speed in different places, the past and the future differ far less than we might think, and the very notion of the present evaporates in the vast universe.
Carlo Rovelli on The Order of Time (youtube)
“For centuries, as long as travel was on horseback, on foot, or in carriages, there was no reason to synchronize clocks between one place and another. There was good reason for not doing so. Midday is, by definition, when the sun is at its highest. Every city and village had a sundial that registered the moment the sun was at its midpoint, allowing the clock on the bell tower to be regulated with it, for all to see.
But the sun does not reach midday at the same moment in Lecce as it does in Venice, or in Florence, or in Turin, because the sun moves from east to west. and for centuries the clocks in Venice were a good half hour ahead of those in Turin. Every small village had its own peculiar “hour.” A train station in Paris kept its own hour, a little behind the rest of the city, as a kind of courtesy toward travelers running late.