The Internet Encyclopedia of Philosophy 22. What Is Essential to Being a Clock? by Bradley Dowden, The Internet Encyclopedia of Philosophy, ISSN 2161-0002, https://iep.utm.edu/frequently-asked-questions-about-time/#H22, 2024/03/28.

22. What Is Essential to Being a Clock? by Bradley Dowden

We use a clock to tell what time it is, and which of two events happened first, and how long an event lasts. In order to do this, the clock needs at least two sub-systems, (1) ticking and (2) the counting of those ticks. The goal in building the ticking sub-system is to have a tick rate that is stable. That means it is regular in the sense of not drifting very much over time. The tick rate in clocks that use cyclic processes is called the “frequency,” and it is measured in cycles per second. The counting sub-system counts the ticks in order to measure how much time has elapsed between two events of interest, and to calculate what time it is, and to display the result.

All other things being equal, the higher the frequency of our best clocks the better. Earth rotations are slow. Pendulums are better. With a quartz clock (used in all our computers and cellphones), a piece of quartz crystal is stimulated with a voltage in order to cause it to vibrate at its characteristic frequency, usually 32,768 cycles per second. So, when 32,768 ticks occur, the quartz clock advances its count of seconds by one second. Our civilization’s standard atomic clock ticks at a frequency of 9,192,631,770 ticks per second.

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The larger enterprise of practical time-keeping for our civilization requires that clock readings be available at locations of interest, including onboard our spaceships and inside submarines. This availability can be accomplished in various ways. A standard clock sitting in a room in Paris is a practical standard only if either its times can be broadcast quickly to the desired distant location, or the clock can be copied and calibrated so that the copies stay adequately synchronized even though they are transported to different places. If the copies cannot always stay sufficiently synchronized (calibrated) with the standard clock back in Paris, then we need to know how we can compensate for this deviation from synchrony.

The count of a clock’s ticks is normally converted and displayed in seconds or in some other unit of time such as minutes, nanoseconds, hours, or years. This counting of ticks can be difficult. Our civilization’s 1964 standard clock ticks 9,192,631,770 times per second. Nobody sat down for a second and counted this number. An indirect procedure is required.