The day I visited Greenwich, England was a chilly, foggy, drizzly one. My friend, Graham, decided the borough would be the best place to begin the day’s tour. I remember the welcome respite from the drizzle as we strolled underneath the River Thames through the Greenwich Foot Tunnel.
Soon, we stopped to admire the famous “Cutty Sark” clipper ship then walked past the National Maritime Museum. Next, we approached the Royal Observatory to an area, paved in brick. I cleaned the mist from my eyeglasses then spotted the Prime Meridian. On impulse, I stood on the actual line. One foot was on the Western Hemisphere and the other on the Eastern Hemisphere. I made a mental note that I was standing at 0-degrees longitude. After a minute or so, I again cleaned the moisture from my glasses, so my friend and I could continue our walk.
If you remember the geography lesson about global coordinates, you know that there is a meridian 180 degrees west and east of 0 degrees. 180 degrees longitude is the geographical international date line. Due to geo-political interests, the International Date Line often deviates from the meridian. The same, irregular manner of designating Time Zone boundaries according to political divisions can be seen on maps that show Time Zones.
The Prime Meridian is the place to define the “Universal Day”. At the International Meridian Conference in 1884, at Washington DC, the local mean time at the Royal Observatory in Greenwich, England was chosen. Greenwich Mean Time was to begin at 0 Hours or “mean midnight”. This designation agreed with the civilian GMT that had been in use in Britain ever since 1847.
The introduction of the atomic clock, a different way of measuring the day, came into being. Coordinated Universal Time, or Universal Time Coordinated, UTC, replaced GMT as the Earth’s Standard Time. Because GMT is now reckoned by UTC, GMT in Britain, is the same as UTC. UTC, was officially inaugurated at the beginning of 1961. The name Coordinated Universal Time was adopted in 1967 by the International Astronomical Union.
Of course, 0-degrees longitude doesn’t only pass through Britain. It passes through France, Spain, Algeria, Mali, Burkina Paso, and Ghana. It Intersects both Poles and becomes the international date line.
Today is Prime Meridian Day, this minor holiday celebrates November 1, 1884, the date that the International Meridian Conference, mentioned above, established the Prime Meridian and specified time zones for the globe. They also determined that every 15-degrees longitude equals one hour.
In most of the United States, this year, we set our clocks and watches back to Standard Time from Daylight Savings Time. So, time is certainly on our minds. As we verify that our timepieces are set to the proper time, we can salute the people who instituted our current manner of defining the “Universal Day” and UTC.