At the same time, new technologies provided much more accurate means of measuring the surface of the Earth.
PRIME MERIDIAN MAP UPDATE
The need for an update to the location of the prime meridian became more and more palpable in the 1980s, as the world grew increasingly interconnected and global navigation and timekeeping became critically reliant on satellites. The line marking the original Prime Meridian. History of time in the UK Satellites Move Prime Meridian
In doing so, however, they did not take into account local distortions of gravity caused by the terrain, causing the telescope to be slightly off. They used a pool of mercury to identify the exact direction of Earth's gravity and, therefore, the planet's center. In addition, a 2015 study suggests that the astronomers who calibrated the telescope even did so on slightly false premises.
This means that measurements carried out at a particular location are not necessarily accurate for other locations. It is slightly squashed at the poles and its mass is not distributed quite evenly. The problem with the Greenwich Meridian of 1884 was that it was based on measurements from a telescope situated in a particular location, which did not take into account the actual shape of our planet. UK doesn't follow GMT in the summer Skewed Gravity Apart from serving as a navigational reference point, the local mean time at the Greenwich Meridian now also served as the basis for the global time standard, Greenwich Mean Time (GMT), before being replaced by UTC in the 1960s. While latitudes are defined by the Earth's shape and movement-the poles at 90° latitude are where the Earth's axis meets the Earth's surface and the equator at 0° latitude marks the middle point between the poles-there is no natural reason for any longitude to be used as the prime meridian.Īt the International Meridian Conference in 1884, with multiple candidates to choose from, that honor was bestowed upon the longitude of the Airy Transit Circle in Greenwich. To understand how there can be two different prime meridians, both being in the correct location for their purposes, it's important to bear in mind that meridians and longitudes are a human invention, so there is essentially no right or wrong way to place them. Since the location of this original prime meridian is defined by the location of the telescope, it cannot be wrong: it is always where the telescope is. It is defined by the location of the telescope, which was originally used to measure the passage of certain stars to feed data into an astronomical coordinate system, which, in its day, served as the basis for global navigation and timekeeping. However, although the world is now using an updated version, the location of the prime meridian is not wrong as such-it's just a different kind of meridian. Navigation systems such as the GPS now use the IERS Reference Meridian (IRM), which runs about 334 feet (102 meters) east of the observatory. It is true that the meridian that runs through the observatory has lost its status as the world's sole reference point for longitude.
So, have they been luring tourists to the wrong place for decades? Not Wrong, Just Different However, if you follow your GPS device to 0° longitude, you will end up a good distance away from the famous line marking the meridian in the observatory's Meridian Courtyard. The observatory is home to the Airy Transit Circle, a telescope designed by George Biddell Airy in the 19th century, which marks the location of the prime meridian, the line running along 0° of longitude, where the Earth's western and eastern hemispheres meet. Since everyone is running around with their own GPS tracker or mobile phones with GPS capability, a visit to the Royal Observatory in Greenwich, London may have become a slightly disappointing affair for some. ©Daniel Case GPS Shows Different Meridian