The tick of a mechanical clock is the sound of it being stopped. Everything that drives a clock, the hanging weight or the wound spring, wants nothing more than to spin the gears round as fast as they will go and be done in moments. What keeps time is the escapement: a toothed wheel and a rocking anchor that catches it, lets exactly one tooth slip by, and catches it again. Every tick you hear is a tooth landing against the anchor at the end of its one allowed step. In a grandfather clock with a pendulum about a metre long, that happens once a second, for as long as somebody remembers to wind it. So what we call a clock going is a clock being held back, sixty times a minute, on purpose, and the time is simply the count of how often it was caught.