Wall Clock

You find yourself in a perfectly quiet room, and the only sound that breaks the silence is that of a wall clock. It keeps its uninterrupted rhythm going with precision. You are almost falling asleep as a patch of afternoon sunshine beams through the window and onto your lap. Your own heartbeat seems to seek to keep the exact pace with the clock. You are very relaxed but not quite asleep. A clock is an instrument used to indicate, keep, and co-ordinate time. The word clock is derived ultimately (via Dutch, Northern French, and Medieval Latin) from the Celtic words clagan and clocca meaning "bell". A silent instrument missing such a mechanism has traditionally been known as a timepiece. In general usage today a "clock" refers to any device for measuring and displaying the time. The clock is one of the oldest human inventions, meeting the need to consistently measure intervals of time shorter than the natural units: the day; the lunar month; and the year. Devices operating on several different physical processes have been used over the millennia, culminating in the clocks of today.