Watches is necessary in every reference system in physics. How do we check that clock is ticking evenly?
Not required by common people, however for scientific purposes there are atomic clocks which are used as gold standards to synchronize and correct other clocks.
See the Wikipedia page of atomic clocks. It explains the underlying mechanism which is based on the electronic transitions of the atom. Why would they change unless nature at a quantum level comes to tamper the transition frequency. If you keep on doing regression then you will never reach your notion of the ideal clock.
Frequency of quantum generator, or atomic clock, can be changed by many reasons :) But Bohr, nature and our experience tells us that transition frequency is constant. Why? It is just a definition. :) Any comment of how to check quantum watches?
Transition frequency is constant, not be definition but by precise observations, battle-tested. As I mentioned earlier the way you are regressing will take you to question "constant". You can set it as per the requirement of your applications, something which does not change in a fermi-, micro-, or milli-second or even an year or a century. Accuracy of atomic clocks from Wikipedia page,
"At this frequency uncertainty, the NIST-F2 is expected to neither gain nor lose a second in more than 211 million (211 × 10^6) years."
Quantum watches are still a subject of research.
http://phys.org/news/2016-05-optical-clocks-redefine-length.html
http://phys.org/news/2016-05-tiny-optical-frequency-clock-accurately.html
http://phys.org/news/2016-02-physicists-implications-quantum-mechanics-philosophy.html
Dear Vikash!
But do you know how is atomic clock tested metrologically ? I am talking about it.
@ Anatoly
https://en.wikipedia.org/wiki/Quantum_clock#Accuracy
"The NIST team are not able to measure clock ticks per second because the definition of a second is based on the NIST-F1 which cannot measure a more precise machine."
Anatoly, with your questoin we arrive at a definition of Time. I am afraid Time (or its evenness) is defined through ticking of some clocks, which we have to believe are running properly :)
If one second suddenly becomes shorter, we will notice that the car passed shorter distance during that very second. But we cannot tell if time went wrong, or the car changed speed. We just believe that the car had no reasons to do that, and assign the effect to the time hopping. Car or clock, all the same
Is it related to General Relativity? Space-time is curved, it is no more homogeneous (as time evenness) in some locations near the planet and we feel it as a gravitation? But if time is becoming faster around all the universe, of course we do not check it. Somebody tried to reduce electromagnetic interactions to some space-time curvature?
Well, what I meant is totally classical.It concerns the definition of physical values: to evaluate smth we compare it with a "TRUE" value. Which we believe is true. For example a 1 meter ruler. Your question was if all 1 cm divisions are the same? In order to answer, we copy one of the 1cm divisions, translate it to the the questionable division, assume that it did not change length during this operation, and compare.
With time intervals we cannot translate a sample interval onto the interval we check, so we claim that some interval is "TRUE" (say atomic oscillation, or Swiss watch) and compare. As the technology develops, we use more and more advanced ticks, but at the bottom there always is something we believe in.
Imagine the time is inhomogeneous (ticks are uneven), how we could notice that? For example as nonconstant speed of a mass, which we expect to have a constant speed. Acceleration means force, and thus uneven ticks are related to Gravity.
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