An Ideal Time

Time is a tricky thing in physics, especially when it comes to measurement. And clocks may not solve this problem in the way we once thought they did, researchers are now saying.

A clock here doesn't mean, simply, the one hanging in your room, but a physics concept. Yes, physics clocks are instruments that measure time, but time as points that can be measured at nearby points in space with infinite accuracy. In short, physics has told us that clocks aren't affected by space and time — they tick along at a consistent rhythm and measure the same amount of time thanks to a principle called "time translation invariance."

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However, theoretical physicists from the University of Vienna and the Austrian Academy of Sciences demonstrated a fundamental flaw in our ability to measure time. In a study published in the journal Proceedings of the National Academy of Sciences (PNAS), the researchers arrived at this conclusion by studying the interplay of  and Einstein's theory of .

"We find that there exist fundamental limitations to the joint measurability of time along neighboring spacetime trajectories," the three authors wrote in the study.

Blurred Times

In quantum mechanics, Heisenberg's uncertainty principle assumes that there's a limit to the precision with which two physical properties — the energy and time of a clock — can be known. On the other hand, there is general relativity's "gravitational time dilation" effect, which describes how the flow of time can be changed by the presence of masses or source of energy.

"However, if time is defined operationally, as a pointer position of a physical clock that obeys the principles of general relativity and quantum mechanics, [that there is an ideal clock to each world line] is, at most, a convenient fiction," the researchers wrote.

In short, the larger the uncertainty of energy, the greater the uncertainty of time. The researchers showed that clocks placed next to one another creates a "blurred" flow of time.

This limitation, supposedly, is a universal one that's not affected by the underlying mechanisms of clocks nor the material they're made from. The research points out the importance of having a more accurate clocks that measure time, as these are crucial for modern technologies — for instance, in GPS devices, which we use on a regular basis.

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