Tag Archive | Prime Meridian

Prime Meridian

Time Is a Construct

October 13, 2020

When one thinks of impressive British cities, London immediately comes to mind. It is, after all, steeped in rich tradition, full of historical buildings, awash in history.

A few miles west of central London, however, is a place also with rich traditions, historical buildings, and brimming with history. It is a place whose name has become common due primarily to the decision by the International Meridian Conference on October 13, 1884.

It was on that date that Greenwich was declared as ground zero, so to speak, for determining – literally – the longitudinal address of every place on earth.

The story began hundreds of years earlier when Greenwich, located a little over 7 miles west of Parliament Square in London, developed into an important maritime port. At the time, it was a separate entity from the capital although it has long since been annexed into the city of London. Its location on a broad section of the Thames river, and proximity to the seat of power, made it a logical location as it is a short 50 miles to the North Sea. It was from this location the British Empire launched its navy and, arguably, several hundred years as the world’s greatest power.

One of the challenges that the seafarers encountered was to develop an accurate navigation system. Using the position of the sun during the day, and astronomical star charts at night, sailors were able to determine their location based on where they started or the “Prime Meridian.”

Of course, it was not only the British who needed this technology. Dozens of “Prime Meridians” were established throughout history. From the Infallible Wikipedia:

Sphere sculpture and ‘prime meridian’ line where you can locate 0 degrees longitude. Photo from Wikimedia

“The notion of longitude was developed by the Greek Eratosthenes (c. 276 BC – c. 195 BC) in Alexandria, and Hipparchus (c. 190 BC – c. 120 BC) in Rhodes, and applied to a large number of cities by the geographer Strabo (64/63 BC – c. 24 AD). But it was Ptolemy (c. AD 90 – c. AD 168) who first used a consistent meridian for a world map in his Geographia.

Ptolemy used as his basis the ‘Fortunate Isles’, a group of islands in the Atlantic, which are usually associated with the Canary Islands (13° to 18°W), although his maps correspond more closely to the Cape Verde islands (22° to 25° W). The main point is to be comfortably west of the western tip of Africa (17.5° W) as negative numbers were not yet in use. His prime meridian corresponds to 18° 40′ west of Winchester (about 20°W) today. At that time the chief method of determining longitude was by using the reported times of lunar eclipses in different countries.”

By the 1800’s, the whole Prime Meridian thing was a mess with dozens of civilized countries establishing their own locations. In Germany it was Berlin, France had Paris, Denmark had Copenhagen and, of course, Britain had Greenwich.

It was the British, however, who led the way. The Infallible Wikipedia continues:

“Between 1765 and 1811, Nevil Maskelyne published 49 issues of the Nautical Almanac based on the meridian of the Royal Observatory, Greenwich. ‘Maskelyne’s tables not only made the lunar method practicable, they also made the Greenwich meridian the universal reference point. Even the French translations of the Nautical Almanac retained Maskelyne’s calculations from Greenwich—in spite of the fact that every other table in the Connaissance des Temps considered the Paris meridian as the prime.’

In 1884, at the International Meridian Conference in Washington, D.C., 22 countries voted to adopt the Greenwich meridian as the prime meridian of the world. The French argued for a neutral line, mentioning the Azores and the Bering Strait, but eventually abstained and continued to use the Paris meridian until 1911.”

Once the French came around, so did the entire world with the term ‘prime meridian’ and Greenwich synonymous.

Personally, I have always found the concept of an arbitrary line stretching from top to bottom of earth kind of weird. And then there is the whole plus/minus hours to figure out how many hours ahead or behind one might be from Greenwich.

Here in Washington State we are eight hours behind until we are not. I find myself constantly having to count on my fingers whenever I read something that establishes a particular event happening at, for example, 11.45 UTC. Which stands for Coordinated Universal Time. Shouldn’t the acronym be CUT? But I digress.

In 2018, the autumnal equinox arrived at 1:54 a.m. on September 23rd in Greenwich. But it was still September 22nd here when it arrived at 6:54 p.m.

Although I’ve never crossed the International Date Line (located in the middle of the Pacific Ocean and drawn in such a way as to not cross any populated islands), my one trip to England involved getting on a plane in Seattle around 9 p.m. Pacific Daylight Time, flying up and over Canada and Greenland, then landing in London the next morning.

My parents’ – who had traveled to Europe before that trip – had a method worked out. They’d arranged for our hotel to be ready earlier in the day. When we arrived it was agreed that we’d all go to sleep for about 3 hours, then get up in the afternoon, and proceed with the local time.

That afternoon, we did a bit of walking about London, went to dinner, and then retired at the same time as most of England’s citizens would. The adjustment was easy.

Of course on the return trip we arrived back home earlier than we left. Talk about mind bending. It took me a solid three days to readjust.

Nowadays I try to avoid taking any flight which involves leaving at night and arriving at my destination the next morning. My theory is that we are only allotted so many ‘all-nighters’ in our lives and I’ve used most of mine. I pulled more than one all-nighter during college and too many to count from when my children were babies.

My children are both now grown so they are no longer inclined to keep me awake all night. It’s my oldest, however, who has coined the phrase “Time Is a Construct.” After all, in the grand scheme of life, does it really matter if it’s 1:53 p.m. or 12:53 p.m.? Perhaps we will find out in a few weeks when ‘time’ falls back.

The one thing I do think I will need to make an exception to are the overnight flight rules. I am sorry I missed visiting Greenwich when I was there before. I’ve decided that, for at least once in my life, I really want to be in the right time and place. Literally.

For those other geeky musers like the author, a couple links: