The Better The Clock The More Entropy It Might Generate

Image Credit: Jul_g/

Time and entropy have a very intimate relationship in physics. The total entropy of an isolated system (such as the universe) always increases. Right in the direction of the arrow of time. For a long time, there has been a suspicion that the two are somehow related although we have yet to find strong evidence for it.

While understanding time itself and its relationship with entropy still elude us, researchers might have had more luck with clocks. It appears that the more accurate a clock is the more entropy it generates. This connection was known for idealized clocks at the quantum level. And researchers wondered if this could be extended all the way to the macroscopic level.

They did not get all the way there, but they were able to get closer to our level. In a paper, accepted for publication in Physical Review X, the team describes a nanometer-thick membrane about 1.5 millimeters long that was made to vibrate like the ticking of a clock.

The vibration was created thanks to an electrical signal sent through the membrane. The higher the electrical signal, the more accurate the vibration. Once the team accounted for other sources of noise, the remaining thermal noise is seen to directly increase with the accuracy.

"If you want a better clock, you have to pay for it," co-author physicist Natalia Ares of the University of Oxford told Science News.

Finding the relation (although different) is certainly exciting but it's one based on a single clock, so similar investigations into every clock would need to take place before we can generalize the results. The findings also highlight that having a clock that generates a lot of entropy doesn’t necessarily mean that it is actually is more accurate. It's not a two-way street.

"The accuracy is only a lower bound on the entropy creation, making it entirely possible for the system to dissipate more entropy at higher drive powers without providing more accurate ticks" the team wrote in the paper. "The fact that we nonetheless see such a consistent linear relationship between the accuracy and the entropy production for a considerable range of cavity and white noise drives, indicates that our clock’s performance is close to optimal and that we are correctly identifying the relevant entropy contributions."

Physicists have recently topped historic records for accuracy in timekeeping. These optical clocks are 100 times more precise than atomic clocks. The measurements now have uncertainties of less than 8 parts per one billion, billion or (or 0.000000000000000008). If we want to go further, our understanding of the relationship between entropy and clocks could become very important.

[h/t: Science News]


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