What the thermodynamics of clocks tell us about the mysteries of time

Surprising new insights about the strange physics underlying how clocks work could transform our understanding of time’s arrow – and hint at how time works at the quantum scale


29 December 2021

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A CENTURY ago, two intellectual giants met to debate the nature of time. One was the French philosopher Henri Bergson, a superstar whose fans caused the first traffic jam on Broadway in New York as they flocked to one of his earlier appearances. He believed there was more to time than something that can be measured by clocks, captured by mathematics or explained by psychology. He argued that the way we experience it, with a duration and direction, could only be revealed through philosophy.

Bergson’s opponent, a physicist called Albert Einstein, disagreed. After developing his theories of relativity he believed time was a physical entity, separate from human consciousness, that could speed up or slow down. Einstein thought that time was interwoven in space in a static cosmos called the block universe which lacks a clear past, present or future.

Almost 100 years later, the question of why the time we perceive is so different from the time postulated in physics is still hotly debated. Now, fresh clues are starting to suggest the devices we use to measure time might be crucial to arriving at an answer.

Those clues relate to the fact that in general relativity, clocks are incorporated into the theory as perfectly idealised objects, with smooth readings that are accurate no matter how much you zoom in, when they actually are anything but. “Clocks are physical things which are made up of physical systems, and so we kind of know that idealisation can’t be right,” says Emily Adlam at the Rotman Institute of Philosophy at Western University in Canada. “A more realistic understanding of clocks may ultimately be the key to …

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