The Start of Time

Today we visited the Royal Greenwich Observatory. Greenwich is home to the Prime Meridian of the World, a line which indicates where point zero longitude on earth is. This line divides the eastern and western hemispheres of the earth.

The Royal Greenwich Observatory is Britain's oldest scientific institution and was opened in 1675 by King Charles II as he wanted to perfect navigation and direction. The Prime Meridian Line was officially defined in Greenwich in 1884 by the Transit Circle telescope. This telescope was built by Sir George Biddell Airy, who was a royal astronomer, and can be seen at the Royal Greenwich Observatory. In the 1880s each town used their own sense of time and decided when the day started and ended. There was no international standard of time, but there was a need for one as railroads and other methods of transportation were being developed. In the late 1880's, the Greenwich Mean Time and the historical Prime Meridian Line were used to rectify this problem. The Greenwich Mean Time is the yearly average of the time each day when the sun crosses the historical Prime Meridian in Greenwich, which happened to be 24 hours. Greenwich Mean Time was used to standardize time, and was adapted world-wide. It is the international standard time we all follow today.

One interesting thing we learned is that while the Prime Meridian is considered point zero longitude, it isn't at the same exact spot the line in Greenwich shows it as because of how the earth's crust is always moving slightly. In the 1980s a new set of coordinate systems were adopted via satellite data and it was found that the actual Prime Meridian Line was actually 102.5 meters to the east of the historic Meridian Line in Greenwich. This new line is known as the International Reference Meridian and is now the only meridian that can be called the Prime Meridian of the world.

-Scott and Breannca


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