VIEWPOINT The Thermodynamic Cost of Measuring Time

T he ability to precisely measure time has had a dramatic impact on society, from the marine chronometers that facilitated navigation in the 18th century, to the satellite-borne atomic clocks that enable the Global Positioning System (GPS) today. But what fundamental limitations does physics place on our ability to measure time? In a new paper, Paul Erker from the Autonomous University of Barcelona, Spain, and colleagues [1] argue that thermodynamics plays a key role in such limitations. Considering a simple model of a quantum clock, they establish a quantitative connection between two of its features—accuracy and resolution—and the “thermodynamic cost” of running it in terms of its heat dissipation and entropy increase. Thermodynamics also lies at the heart of our perception that time flows inexorably forwards from the past to the future. These results therefore link our ability to measure time with the flow of time itself.