There are so many things I take for granted in my life, and especially when I travel. I carry in my pocket more computing power than existed in the entire world in 1980. My phone tells time and always knows where I am. It’s hard for me to remember a time before smart phones, let alone to try to imagine life without any sort of technology.

Close your eyes and imagine, for a moment, having to rely on the position of the sun to tell time. Picture having to gaze up at the stars to know direction, or a vague location on the planet’s surface. That was the way life used to be… until Greenwich.

Today, Greenwich is just a cute part of London in the southeastern corner on the south bank of the Thames. It features a cute town core, a pretty solid market, a beautiful college, and a couple of museums on the outskirts of a large park. Up a hill in that park, you’ll find the reason most people have heard of Greenwich: the Royal Observatory.

The Royal Observatory

In 1675, King Charles II commissioned the observatory on a site chosen by renowned architect Sir Christopher Wren. It was on a hill, removed from the city (although today it connects via mass transit to downtown), and easy to reach via the Thames. In addition, Charles created the position of Astronomer Royal to inhabit the observatory, to chart the stars, and permanently – it was hoped – solve the problem of longitude in navigation.

(Note: some things below might be a bit technical. I have tried to simplify them to be understood, but I apologize in advance for anything that is a bit tough to grasp, or for any circular language I use.)

Latitude is easy to measure, since the position of the sun at noon – combined with a little trigonometry – will give you your location relative to the equator, the line that bisects the Earth along its rotational axis. It can also be measured at night in relation to Polaris, the North Star. Longitude is harder, both in practical terms as the sun moves east-west, and in term of definition since there isn’t an easy non-arbitrary line bisecting the planet into eastern and western hemispheres as the equator does for northern and southern.

The planetarium side of the observatory is free to enter!

Measuring longitude requires knowing the difference in time between your current location and a location where the longitude is known. Therefore two things were necessary: the establishment of a set longitude (called a meridian) at a known point, and the ability to accurately measure the time locally in relation to at that known point.

The observatory was designed by Sir Christopher Wren, and completed for a cost of £520. When it opened, it did so with two clocks, which were then the most accurate in the world. They had 13-foot pendulums, and were accurate to within 7 seconds per day. (Think about how difficult our lives would be today with clocks being off by even this much, roughly 42 minutes per year.) However, thanks to those early accurate clocks, Greenwich became known as the center of time keeping in England, and for most of the world. Even today, time zones are measured in their distance from Greenwich Mean Time. (I sit here in Los Angeles on Pacific Time, also known as GMT -8.) Subsequent clocks, ever more accurate, satisfied the second condition to establishing longitude: time was able to be truly accurately determined, and it was easily known in Greenwich.

The official Greenwich clock has changed over the centuries.

As the years went by, the importance of Greenwich’s physical location came to matter even more. With the work done by astronomers royal in figuring out calculations of longitude, it was key to have a line like the equator, even if it was arbitrarily placed. And so it was, with the establishment of the Greenwich Meridian, to be called zero degrees. (180 degrees, the pure opposite of this, became the basis for the international date line, as noon – the time necessary for sun positioning – in Greenwich meant midnight along that line.) This satisfied the other condition: a base meridian from which to measure longitude.

As measurements became more precise, and those at the observatory led the world, there was a conference in 1884 formally adopting the Greenwich Meridian as the world’s first Prime Meridian. It has since been replaced by the IERS Reference Meridian, about 335 feet away. However, the Greenwich Meridian, running down the center of the courtyard of the observatory and off into the park, can still make a nice photo for science enthusiasts like me!

Standing on the Greenwich Meridian

There are two parts of the Greenwich Observatory that can be explored: the historical building which has a hefty fee, and the planetarium across the courtyard, which is free. For those who choose not to enter the observatory, there is also a wall (and walkway) just outside the complex that has the meridian running down it. Surrounded by the park, and with a wonderful view from the top of the hill, it is a worthy place to visit even without seeing the inside of the building.

Check out this view!

Greenwich has truly changed the world. What we know today, and the ease at which we know it, would not have been possible without this incredible place and the technological advances made here. It is worth a trip just to pay homage to that.

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