TELLING TIME (GREENWICH MEAN TIME)
Our sense of time is connected to biology and astronomy – the patterns of nature and the patterns of the universe. Living things react to natural cycles. Animals migrate and breed, tides rise and falls, plants bloom and from early on, people have noticed the correlation of those events with the movements of the sun, moon, and stars.
The technology developed to organize time, however, is as much about the future as it is about the present and past. It gives individuals and societies the ability to anticipate when important events are likely to occur and to decide when certain things should happen in response. Knowing that animals migrate when it turns cold is one thing; advance knowledge of when that is likely to occur informs the hunting plan.
Clocks and calendars are the tools that allow this sort of rhythmic planing. They evolved over thousands of years as people studied patterns in the Earth and Sky and began associating changes in the weather or other phenomena with the positions of heavenly bodies. The basic divisions of our modern calendar remain astronomical: A day is the time it takes Earth to spin on its axis; a Year is the time it takes Earth to orbit around the sun, and a month roughly reflects the time it takes for the moon to pass through its cycle of phase.
The first calendar emerged in Sumeria almost 5,000 years ago and used the position of the sun and moon to coordinate agriculture and religious rituals and sacrifices. The Chinese, Maya, Greek, and Roman civilizations all developed calendars suited to their own societies and view of the world. The Romans, for example, used an eight-day week as the basic unit for reckoning time, a period reflecting the rhythm of their commerce, for every eighth day was market day.
GMT (GREENWICH MEAN TIME)
As transportation and communication grew faster in the 1800s, coordinating events between different locations became problematic. High noon in one city is not concurrent with high noon in a city far to the east or the west. This issue was particularly nettlesome for officials trying to coordinate the schedule for the United States’ expanding railroads.
In 1883 they recommended a standardized system that separated the globed into 24 time zones, each covering 15 degrees of longitude and deferring from the adjacent zone by one hour. The Royal Greenwich Observatory in suburban London became the location used around the world to fix the prime meridian – the longitudinal line assigned 0′ – and Greenwich mean time gradually became the world’s reference point for synchronizing watches.