Sometimes it’s the small things, the things a person takes for granted, that get a person out of sorts if not in place or wrong. Ever heard of a blue stop sign? No, and there’s probably a good reason for it, which will not be explored here. But think of the confusion a blue stop sign might create. It’s one of those very small, detailed conventions which we never give much thought to, but could really make a person’s day bad. Time is also one of those things most of us take for granted. But it’s not as small a thing.
Specifically, Zulu time. For most of the rest of the world, the term more commonly used is Greenwich Mean Time (GMT) or Coordinated Universal Time (UTC). But in the US military and other three-letter government agencies, the standard terminology is Zulu. What do all three terms mean? And what do they have to do with space operations? Perhaps a short history lesson involving cartography, politics, military, and commerce is necessary for illumination.
A few hundred years ago, the British (yes, the same ones responsible for Mr. Bean and Red Dwarf) were very interested in giving their ship captains the ability to locate a ship’s position in the ocean with great accuracy. After all, when a country is a naval and commercial power, knowing one’s precise location makes things simpler (it wasn’t unusual for some navies to get lost), so geographic coordinates were used. This meant they needed two precise measurements, the latitude and the longitude.
I will use the game, Battleship, to quickly illustrate. Imagine the globe, flattened and in front of you like the Battleship board (if you can’t imagine it, use the picture above). You remember the grid with letters across the top? Those letters and the columns under them represent longitude. And the numbers on the left hand column of the board? Those, as well as the rows to the right of them, represent latitude. So when you’re attempting to sink an opponent’s ship, you would say something like “A,4!” So you’re actually calling out the longitude and latitude of the area you’re targeting, hoping to sink a ship. The letter and number together become a geographic coordinate (a cartographic crosshair). Normally, real-world geographic coordinates are all numbers, stated with latitude first, then longitude—and they are more precise than what’s used in Battleship. There are many great sites and explanations of the all these: geographic coordinates, latitude and longitude. Go to them if you really want to get into the details.
What I recommend is for you, dear reader, to just try to understand there was a need for a common reference point for British ships to navigate the oceans accurately. This reference point, called a Prime Meridian, ended up as the longitude line running through the Royal Observatory in Greenwich, England, from North to South Pole. This means that Greenwich’s longitudinal coordinate is 0 degrees. If you go west, it can go as high as +180 degrees. If you go east, you get to -180 degrees. The Prime Meridian was so important, other countries, such as France, the Netherlands, Belgium, Spain, Portugal, and more, had their own Prime Meridians—some for longer time periods than others. So, what do all of these meridians have to do with time?
Establishing the Prime Meridian is just part of determining the longitude and a ship’s location accurately. The other part was time, and inventing the necessary technology (and terms) to know time accurately. Accurate time was so important to the British government that, in 1714 AD, they offered a bounty of 20,000 British pounds to the first inventor who could “develop a method for determining the longitude within 56 kilometers.”* And that wasn’t as easy as it sounds…more about that tomorrow.
*Citation: Graham-Cumming, John, The Geek Atlas: 128 Places Where Science & Technology Come Alive, O Reilly, 2009, Chapter 049, page 185.
- Daily Prompt: Far from Home-Greenwich Mean Time line (GMT) (sabaslog.wordpress.com)
- Exploring the Delights of Greenwich (traventure.net)
- The Confusion of Time and its Rescue by GMT (mangosalute.com)
- ED FISHER: Welcoming the return of Standard Time (themorningsun.com)
- Opinion: How the Prime Meridian Changed the World (news.nationalgeographic.com)
- Gmt (ldncaroline.wordpress.com)
- observatory (mapjd.wordpress.com)
- Greenwich Mean Time (latanyawhite.biz)
- Greenwich Prime Meridian (pleasureandpayne.com)