Time, Where does it come from?
This is part of a two part series on time measurement. Part 2 will explain how to obtain accurate time measurement in Java. This first part explains the general concept of time measurement. How do we measure time? With a clock of course. So how do we build a clock? The first thing we need is to observe something that occurs at a constant rate. Humans have built clocks based on observations of changes in their environment that appeared to occur at a constant rate. Sundial Some of these earliest clocks were Sundials. The shadow cast by the Sundial moves based on the rate of rotation of the earth on its axis. This observation of the Earth's rotation is what Greenwich Mean Time was based on. At the Royal Observatory in Greenwich astronomers would observe the sun and other stars in order to calibrate their clocks. In principal on average the sun would appear directly above in the sky at 12h00.00. This is why its called Mean time. The current ...