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How Does a Clock Measure Time?

  1. Mar 23, 2008 #1
    It is certainly within the realm of rational scientific inquiry to ask, not simply what a clock measures, but it what manner it measures. These are contextual to an experimental science.

    1) In common to all clocks, how do clocks measure time?

    2) Are there any clocks (that one actually observes from time to time) that will maintain accuracy without correction from external energy?

    Certainly not a sundial. Like a quartz watch it needs external energy to maintain its periodicity--just on a much larger time scale.

    3) Do all clocks in operation involve periodic repetition?

    4) Can a clock be measured without effecting its accuracy?

    In a sub-forum devoted to relativity it is natural to recognise the unification of space and time, as well as inquire about their differences beyond a negative sign in the metric.

    5) A yardstick in operation does not increase the entropy of it's environment (Or does it?). Are there any clocks for which this is true?

    6) A yardstick in operation measures the distance between two space-time events where clocks at each end of the stick are synchronized, right?

    7) As in 6), but when measuring with a clock, what are the yardsticks doing?

    After some of the wild speculations within a recently locked thread, it’s probably a good idea not to confuse, without justification, what a clock measures with how it measures.
  2. jcsd
  3. Mar 23, 2008 #2


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    Staff: Mentor

    Yes. And as such, you'll get a very short leash in this thread. The questions were already answered - people just refuse to accept the answers. For example:
    A sundial does not have batteries and can be used to measure time for eons with high precision. The moon slows the earth's rotation, so it isn't perfect, but so what? The principle is sound. If you want something similar that tells better time, how about a pulsar?

    No clock (or any other measuring device, for that matter) is perfect and the act of taking any measurement (whether time or length) requires the use of energy (yes, even a meter stick). This is irrelevant to the nature of those measurements.

    No clock that I am aware of requires energy to maintain its accuracy, only to run. There is an important distinction to be made there. Clocks either run or they don't - the energy input does not affect the rate at which the clock runs (otherwise, they'd be lousy at telling time).

    If you cannot accept straightforward answers without weaseling, there is nothing to discuss.

    Now, the others (already answered as well, but...):
    All clocks count periodic events and record (by simple proportional conversion) the resulting measured time on some sort of display.
    Yes. This is why energy flow is irrelevant - in fact, undesirable - to the functionality. Energy flow is very difficult to keep constant. Periodic motion is not.
    That is worded badly. Clocks measure time, people don't measure clocks. So the question as phrased is largely meaningless. I think what you are asking is whether a clock can perform its function without affecting its own accuracy - if it couldn't, it wouldn't be a very good clock. Some mechanical clocks may affect the periodic motion by recording it, but this gets calculated into the clock rate. Better clocks do not disrupt their own rate. A sundial, for example, does not interfere with the rotation of the earth. An atomic clock does not interfere with the oscillation of a cesium atom.
    All measuring devices, including a yardstick, require energy to use them. If nothing else, you need light to read a yardstick and your body needs energy to process the information. Don't brush that off as trivial - it isn't (or if it is, it is just as trivial as the fact that a sundial doesn't need batteries). It is akin to an automated measuring device (such as a laser tape measure), which, of course, has batteries. For a sundial or a meter stick, your eyes are what records and processes the measurement, so no other power source is required. If you want something that works better than your eyes - whether a clock or a distance measuring device - it'll need batteries.
    Clocks don't have anything to do with how a yardstick works. And I'm not sure what that has to do with anything.
    Similarly, yardsitcks are not required for reading a clock.
    Last edited: Mar 23, 2008
  4. Mar 23, 2008 #3
    It's your sandbox. Knock yourself out.
  5. Mar 23, 2008 #4


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    I presented a point of view which was ridiculed by a forum administrator (who refused to discuss it and simply locked the thread) so I feel that the thought police will keep me from expressing my views. I was not trying to present a theory of everything or my own pet grand unified theory. I simply presented a simple argument and was hoping to discuss the issue with others but no respectful discussion was allowed. I do not consider myself a crackpot (I have a PhD from an ivy league school and ten years of teaching experience) and did not consider my idea completely crazy (after all, a related point of view is part of th eloop quantum gravity approach) but evidently I was considered a crackpot. I have had high esteem in the quality of the posts and people here at physicsforums.com but this event really disappointed me.

  6. Mar 24, 2008 #5


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    Staff: Mentor

    Yep. And you're either here to learn or you're not. You've clearly made your choice. Locked. And don't restart it.
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