Energy and the Perception of Time

Marine Chronometer in the Science Museum, London

Strange as it might sound, the evolution of energy has greatly affected our perception of time. Transportation technologies improved with bigger and stronger means of propulsion meant we traveled faster. The faster we traveled, the need to measure time accurately increased. Many time-keeping technologies were developed to better quantify the passage of time during trips. Along with more accurate clocks came more advanced things we could do.

In the middle ages, the passage of time was measured by seasons. Clocks took advantage of the regularity of a swinging pendulum to measure the passage of time. However, a swinging pendulum did not work on ships, as the rocking motion of the ocean would disrupt the motion. Christopher Columbus sailed the Atlantic Ocean using a 30-minute long hourglass. The cabin boy’s duties included watching the glass and reversing it every 30 minutes for the entire duration of the trip.

The invention of the spring-powered clock revolutionized maritime travel. Ships could know exactly how long they have traveled and their onboard clock would be synched with both the departure and arrival port. Ports would know if a ship was on-time or late. With better timekeeping, the ship trade blossomed.

The arrival of the railroad made the accuracy of clocks even more pressing. Passengers needed accurate clocks (pocket watches) to let them know when a train would leave. Likewise, train stations across the UK had to be synchronized so that train departures and arrivals could be standardized. It was during this era that Greenwich became the global standard of time.

The global network of GPS satellites all carry highly accurate atomic clocks. They work by recording the time elapsed between pings and triangulating positions. Since the GPS satellites are in orbit, the satellites need to know how far they’ve traveled in order to calculate how far a person has traveled. This requires highly accurate atomic clocks that even take into account Einstein’s theory of relativity. That’s quite a bit of advanced physics just so your smartphone knows where you are!