A man goes for an audition to be permitted to compete in the swimming events at the Paralympics. The officials refuse him and he demands to know why. "Because you have no arms or legs." "That's irrelevant," he says. "Throw me in and I'll prove it to you." They throw him in. He quickly sinks and is on the verge of drowning when they haul him out and resuscitate him. "So now do you accept our decision?" they asked. "No," he said. "Next time, I'll just have to flap my ears a bit harder."
At rest, my heart rate is about 60 beats per minute - which could almost be said to be like a clock.
Maybe the setting of the duration of a second was based on the normal healthy resting heart-rate. Though I suspect it probably had more to do with convenient arithmetics.
Anyway, my heart rate goes up and down in response to all sorts of physical exertions and emotional situations - so in that, I am nothing like a clock.
Odd you should mention that. When I was in the US Navy, I was in charge of one of the most accurate clocks in the world. I won't go into the science of it but it was within a billionth of a second of the standard.
But even the best mechanical, electric motorized and quartz crystal-based clocks develop discrepancies, and virtually none are good enough to realize an ephemeris second. Far better for timekeeping is the natural and exact "vibration" in an energized atom. The frequency of vibration (i.e., radiation) is very specific depending on the type of atom and how it is excited. Since 1967, the second has been defined as exactly "the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom" (at a temperature of 0 K). This length of a second was selected to correspond exactly to the length of the ephemeris second previously defined. Atomic clocks use such a frequency to measure seconds by counting cycles per second at that frequency. Radiation of this kind is one of the most stable and reproducible phenomena of nature. The current generation of atomic clocks is accurate to within one second in a few hundred million years.
Atomic clocks now set the length of a second and the time standard for the world.
Element 99 