Clock History Part one

              The ability to keep time is one of humanities most early inventions. Before what we know as a modern clock was made, the sun was used in order to keep track of time. By placing a  rod on a flat surface, it was possible to know the time of day by the use of the shadow hitting the surface. As the sun moved along the sky, the shadow would change at a consistent rate. This is known as a Sundial. The flaw of the sundial is obvious; it has to be day time, and sunny for it to work. The technical term for the stick that stands up is a Gnomon.
               Another early timepiece is the hourglass. Hour glasses are simple devices that use falling sand  in two glass domes. The amount of time it takes for all the sand to fall from one side to the other is known, so it was possible to keep track of time with this device. The size of the glass, the amount of sand as well as the size of the opening that connects the glass domes.
               A third example is the water clock. Similar to the hourglass, a simple water clock called a clepsydra  (water thief) could be used to keep track of time. In ancient Greece, its uses included time keeping for trials, time keeping for appointments and an athletic stopwatch as well as a tool to get a reading on a persons pulse