GEOCHRONOLOGY

Time

Time is both a philosophical and physical concept. Our awareness of time lies in the ability to determine which of two events occurred before the other. We are conscious of a present in which we live and which replaces continually a past of which we have a memory; we are also conscious of a future, in some aspects predictable, that will replace the present. The progress of time was visualized by Sir Isaac Newton as a river that flows involuntarily at a uniform rate. The presumption that time is an independent entity underlies all of classical physics. Although Einstein's Theory of Relativity shows that two observers moving relative to each other will have different perceptions of time, physical phenomena are influenced by this relationship only when velocities approach the speed of light. In everyday usage and in non-relativistic science the Newtonian notion of time as an absolute quantity prevails.

The measurement of time is based on counting cycles (and portions of a cycle) of repetitive phenomena. Prehistoric man distinguished the differences between day and night, he observed the phases of the Moon and was aware of the regular repetition of the seasons of the year. From these observations the day, month and year emerged as the units of time. Only after the development of the clock could the day be subdivided into hours, minutes and seconds.