Why Are Hotter Watches Extra Correct – Watts Up With That?

LANCASTER UNIVERSITY

Research news

PICTURE: Clocks permeate every aspect of life, from the atomic clocks that underlie satellite navigation to the cellular clocks in our bodies. Show more CREDIT: LANCASTER UNIVERSITY

A new experiment shows that the more energy a watch consumes, the more accurate the measurement of time.

Clocks permeate every aspect of life, from the atomic clocks that underlie satellite navigation to the cell clocks in our bodies. All of them consume energy and give off heat. A kitchen clock, for example, uses up its battery. In general, the most accurate clocks use the most energy, which indicates a fundamental relationship between energy consumption and accuracy. An international team of scientists from Lancaster, Oxford and Vienna wanted to test this.

For this purpose, they built a particularly simple clock, which consisted of a vibrating ultra-thin membrane several tens of nanometers thick and 1.5 millimeters long, which was built into an electronic circuit. Every vibration of the membrane produced an electrical tick. The ingenious aspect of this design is that it is powered simply by heating the diaphragm while all of the energy flow through the watch can be measured electrically.

The scientists found that the more heat it delivered, the more accurate the clock. In fact, the accuracy was directly proportional to the heat released. To make the watch twice as accurate, they had to deliver twice as much heat.

The experimental team consisted of Dr. Edward Laird from Lancaster University, Professor Marcus Huber from Atominstitut, TUWien, Dr. Paul Erker and Dr. Yelena Guryanova from the Institute for Quantum Optics and Quantum Information (IQOQI) and Dr. Natalia Ares, Dr. Anna Pearson and Professor Andrew Briggs from Oxford.

Their study, published in Physical Review X, marks the first time a measurement has been made of entropy – or heat loss – produced by a minimal clock.

Understanding the thermodynamic costs associated with timing is a key step in developing future technologies, as well as understanding and testing thermodynamics as systems approach the quantum realm.

It also shows a similarity between the operation of a clock and a steam engine. With a steam engine, there are fundamental constraints on how much heat we need to deliver to do the amount of work we want. This limitation is the famous second law of thermodynamics that is central to modern engineering. What this experiment suggests is that clocks, like motors, are constrained by the second law, their output being accurate ticks rather than mechanical work.

Dr. Edward Laird of Lancaster University said, “The subject of thermodynamics, which contains the most basic principles of nature, tells us that there are two types of machines that we cannot operate without giving off heat. One is the mechanical engine that gives off heat to do work and the other is the computer memory that gives off heat when it rewrites itself. This experiment – in conjunction with other work – suggests that clocks are also limited by thermodynamics. It also begs an interesting question: are all possible clocks limited in this way, or is it just a property of the ones we have studied? “

Interestingly, many everyday clocks have an efficiency that is close to the predictions made by scientists. For example, their formula predicts that a wristwatch whose accuracy per tick is a fraction of ten million must consume at least one microwatt of electricity. In fact, a simple wristwatch typically only uses a few times as much. The laws of thermodynamics discovered in the 19th century are still being used today.

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From EurekAlert!

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