Why greenwich for prime meridian

Senior lecturer in physical geography and natural hazards, Coventry University. Matthew Blackett does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment. But we now know that the line, a physical representation of which is visited by thousands of tourists every year, should more precisely be 0.

How did the Victorian astronomers who created the Meridian get their calculations wrong? It comes down to the fact that the Earth is not a perfect sphere. This practice then led to GMT being used worldwide as a standard time independent of location. In the following years, GMT was adopted across the island of Great Britain by the Railway Clearing House in and by almost all railway companies by the following year.

In the past, GMT has been used with two different conventions for numbering hours. The long-standing astronomical convention, dating from the work of Ptolemy, was to refer as zero hours and, on the other hand, the civil convention referred to midnight as zero hours dating from the Roman Empire. There were no national or international conventions which set how time should be measured, or when the day would begin and end, or what length an hour might be.

When the railway and communications networks expanded in the s and s, there needed to be an international time standard.

Greenwich was chosen as the centre for world time. Find out more about Greenwich Mean Time. Find out more about Airy's Transit Circle. Where longitude is the distance east or west of the Prime Meridian line, latitude is measured by the distance north or south of the equator. The intersection between these two invisble lines is in the middle of the Atlantic Ocean.

It's a bit harder to get a selfie standing on this spot! Between and 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. The IRM passes The entire Observatory and the historic Prime Meridian now lie to the west of the true prime meridian.

They chose the meridian passing through the Royal Observatory in Greenwich, England. The Greenwich Meridian became the international standard for the prime meridian. UTC never changes for daylight savings or anything else.

Just as the prime meridian is the standard for longitude, UTC is the standard for time. All countries and regions measure their time zones according to UTC. There are 24 time zone s in the world. If an event happens at a. The event happened at p.