Eastern And Western Hemispheres
On Earth, there are two types of people: those who consider themselves East-enders and those who see themselves as West-enders. While the reasons for this may vary from country to country, one thing is certain the division between Eastern and Western hemispheres is very real. One can hardly imagine his or her world without it but the divide only came about relatively recently in human history. For thousands of years of recorded history, longitude was measured from a different perspective.
Until 1884, even the greatest explorers and navigators had no clue why there was sunrise and sunset twice a day; or why ships on earth would never hit an island that was out at sea, South Greenwich Forum (southgreenwichforum.co.uk). Being in England, at the western end of Europe, means that we are at approximately 51 degrees east. That fact is not too surprising. What might be surprising to you though is the distance on Earth between the most westerly point on the line and the most easterly point.
It is literally a matter of inches! Take a look at our little globe below, which shows the Line of Longitude that we started out on, being marked as 0 degrees along it's way across Earth. Pacific and Atlantic oceans. The International Date Line is an imaginary line of longitude that connects the North Pole with the South Pole. Ocean currents, especially in the Pacific, rotate in a clockwise direction, which means that if you travel west, you will return to the same date.
This was taken from a list of countries in each hemisphere. Now take a look at the map. The World is divided into two halves by what seems to be an imaginary line that runs from the North Pole, down to the South Pole. The line is called the Equator, which means 'equal in height'or 'same height'. And it runs right through Greenwich, London! along with the exact center of Earth. ". And better yet – all the sights are right there on your doorstep.
Who Decided That The Prime Meridian Should Be In Greenwich?
There are 24 time zones across the world. Some of them are made up of a simple offset from Greenwich. This means that even if you live in a place where there is no obvious relationship between longitude and time, you have some kind of relationship to the Prime Meridian, through your use of GMT as a time zone. The Prime Meridian has become a fixed reference from which all other measurements or divisions of longitude are based.
Today we live in an era where global positioning systems have rendered the exact location of ‘0’ immaterial, but it’s worthwhile noting that there was a significant amount of debate and politicking over this decision at the time, with several worthy candidates (including Paris) vying for pole position. Why should you listen to me?. Well, let's see. I've been a Royal Observatory researcher (judging from my degree and job title, it was a long time ago).
I'm the author of the book 'Longitude'which was made into a successful TV series. I've been lucky enough to be involved in all kinds of projects and research relating to astronomy and the history of science over the past 20 years. And on top of that, I live on line of longitude 0, halfway between Greenwich and Paris. How and why did this happen? Why was the Prime Meridian chosen to run through Greenwich, England? How did London come to be the center of time for the whole world? These were some of the questions I tried to answer when I was recently in London.
Has The Meridian Line Moved?
The International Meridian Conference took place in Washington DC, USA resulting in the adoption of the World Geodetic System 1984 (WGS84). This is often referred to as the "Geodetic Reference System 84" (GRS 84) or the "International Terrestrial Reference System (ITRS '80)" and replaced the Geodetic Reference System 1966 (GRS 66). Has the meridian line moved since 1988? I thought it had, so I did some digging. Turns out that as of 2017 the celestial meridian uses 103 degrees minus 0.
28 degrees west longitude (103° 0. 28°W 102. 52°W) which is 1. 85 minutes of arc east of the original meridian line at Greenwich (102° 23'28"). The new coordinate system is usually known as International Terrestrial Reference System (ITRS) and has replaced the now defunct geodetic datum ‘The World Geodetic System 1984’ (WGS 84) which, while widely used for positional measurements including navigation, was invalidated by satellite data. Between 1984 and 1988 an entirely new set of coordinate systems were adopted based on satellite data and other measurements and required a prime meridian that defined a plane passing through the centre of the Earth.