What is GMT | Definition, History, Need, Work, Begin, Full Form of GMT

GMT

Contents:

1. INTRODUCTION
2. What is the definition of GMT?
3. What is GMT?
4. What is the full form of GMT?
5. How did GMT begin?
6. How does it work?
7. Where is the GMT Time Zone?
8. How did the railways make GMT the UK time standard?
9. How did GMT become the international standard?
10. Why do we need GMT?
11. What are the other Time Zones?

INTRODUCTION:

Greenwich Mean Time (GMT) refers to the mean or average solar time at the Royal Greenwich Observatory in London, and which was adopted as the universal standard time.

Historically astronomers used Greenwich Mean Time (GMT) with zero moments at noon; the day began at noon to measure time. The Civil convention used midnight zero moment. However in 1925, GMT was adopted by the Astronomers and the day began at midnight, hence midnight was zero moments. Coordinated Universal time has now replaced GMT and zero moments are still midnight, but the difference between both is small.

Definition of GMT?

GMT means Greenwich Mean Time and refers to the average or mean solar time or clock time at the Royal Greenwich Observatory in London beginning from midnight. Noon Greenwich Time does not mean when the sun at Greenwich meridian is at its peak, the difference is due to the irregular rotation of the earth.

Prime Meridian is the meridian at Longitude 0o. It does not account for daylight saving and it is the Standard time used by the United Kingdom, Ireland, and some countries in Africa and Europe.

What is GMT?

Greenwich Mean Time (GMT) means the sun is the average of the time it passes through the main meridian of the clock at the Royal Greenwich Observatory. This indicates that the clock time at the Observatory instead of the year-round solar system changes as the Greenwich Meridian passes. The length of each day measured by the clock equals the average length of the solar day and ensures that the standard time is maintained.

Solar time unlike GMT varies constantly through the year as the interval that the sun crosses the Greenwich meridian lines varies due to the earth’s elliptical orbit and the irregular daily rotation of the earth.

Solar time is measured by the Earth's rotation relative to the Sun. Clear solar time can be obtained by measuring direct observation of the sun, although clocks and clocks measure average or average solar time, which refers to the time measured by observation. The year traveled at a similar pace.

What is the full form of GMT?

GMT stands for Greenwich Mean Time 

How did Greenwich Mean Time begin?

In 1675 John Flamsteed was appointed by royal warrant, the first Astronomer Royal by the British monarch, Charles II as well the establishment of the Greenwich Royal Observatory in London. Greenwich was a park and palace near the Thames Bridge in London

He was responsible for publishing a set of tables which facilitated the conversion of Solar time to Mean Time. He thereafter brought the finest pendulum clocks and installed them at the Greenwich Royal Observatory, which was set to local time.  Greenwich Mean Time was obtained as the average of the Time when the sun passed through the meridian at Greenwich at longitude 0o, from this humble beginning GMT was born and was popular with astronomers.

It facilitated naval and maritime exploration especially of the new world; however, usage was not widespread as many major cities used local times. The British Nautical Almanac was made available in 1676 by Nevil Maskelyne, the fifth Astronomer Royal of Greenwich Royal Observatory. These Navigational charts enhanced explorations at sea and facilitated the greater acceptance of GMT.

How does it work?

Greenwich Mean Time (GMT) works by using the yearly average or mean of the time each day the Sun passes through the Prime meridian (Longitude 0o ) of the Clock at the Royal Greenwich Observatory, London. This implies that it is the clock time at the observatory rather than the solar time which varies throughout the year as it crosses the Greenwich meridian. Each day measured by the clock has the same length which is equivalent to the mean or average length of a solar day, and this ensures standard time is maintained.

The Prime Meridian is the basis for all the time zones in the world and how to calculate it. Every fifteen degrees in Longitude is equivalent to a one-hour time differential.

Where is the GMT Time Zone?

The Greenwich meridian or Longitude Zero runs from the North Pole to the South Pole and passes through the Royal Observatory and also known as Prime Meridian. The Greenwich Mean Time zone is the Time zone that refers to all the countries that lie on this meridian such as the United Kingdom, Northern Ireland, and some African countries. However, the United Kingdom and Ireland do not use it from October to March during Daylight Saving Time.

Countries on the East of the Meridian are ahead of Greenwich Mean Time, however, those on the West are behind of the GMT.

How did the railways make GMT the UK time standard?

The early1800’s local times were used by the various cities, however, with the widespread use of railways, the various local times presented big challenges to passengers and operators in the railway industry. This created the need for an acceptable time for the industry. Before this time the GMT had not generally adopted. Then the British railway industry initially began using the Greenwich Mean Time (GMT) for its operations to eliminate the confusion created by various local time zones until it was formally adopted. In 1847 the British Railway Clearing House adopted the GMT as its official time and was thereafter known as Railway Time.

In the late 1850’s many public places in Britain started adopting the Railway Time as it gained popularity. However, it was in August 1880 that Greenwich Mean Time known as Railway Time was adopted as the legal time in Britain by an Act of Parliament.

How did GMT become the International standard?

The United States of America had over three hundred local time zones which were quite challenging for the operators of the American Railway industry and their patrons, as they struggled to find a solution. This was later narrowed to one hundred local times zones but it still posed difficulties for the American railway industry.

In November 1883, the Greenwich Mean Time was also adopted by the United States of America, and the United States then had four time zones. During the International Meridian Conference held in Washington D.C, United States of America, Greenwich Mean Time was adopted internationally in November 1884 with the creation of 24 Time zones. Thus GMT became the International Time Standard.

Britain played a key role in the international adaptation of GMT due to the superiority of the navigational charts from the Royal Greenwich Observatory, London as well as the efforts Sir Sandford Fleming, who was one of the conveners of the conference.

Why do we need GMT?

The GMT was the origin and basis for the calculation of several time zones worldwide and more than seventy percent of the world trade used navigational charts based on Greenwich Meridian as the Prime meridian. The accuracy of the Royal Greenwich Observatory navigational data also was a factor that facilitated its adoption.

The conference confirmed the Greenwich meridian as the Prime Meridian and the Greenwich Mean Time as the International Time. Thus all time zones use GMT as a reference point.

The first clock to show the public GMT was installed at Gate of Greenwich Royal Observatory, London in 1852 was known as the Shepherd Gate Clock. GMT was an international civil time from 1884 to 1972.

In January 1972 the GMT was replaced by Coordinated Universal Time as the International Civil Time which is operated using a group of atomic clocks. The atomic clocks have greater accuracy and were set to synchronize with the earth’s rotation. But since the rotation varies there are still small differences between the clock time and natural time, adjustments are made to harmonize it with the earth’s rotation. Initially, France did not accept the Universal Coordinated Time UTC due to some dispute with Britain but adopted it in 1978.

 However GMT it still a legal time in Britain and is used by the British Broadcasting Corporation, Royal Navy, and African and European nations. Some of the Countries that use GMT as legal time include

Ghana, Gambia, Burkina Faso, Liberia, Ivory Coast, Mali Mauritania, Iceland, and Togo

What are the other Time Zones?

The United States of America established standard time with Act of 1918. China uses only one time zone despite having a territory greater than 15 degrees Longitude and has a standard time UTC +08:00 or (GMT +8) China standard Time is eight hours ahead of GMT Below are the four-time zones for the United States of America.

Eastern Standard Time EST is GMT-5
Central Standard Time is GMT -6 
Mountain Standard Time is GMT -7 while for UTC -6
Pacific Standard Time is   GMT - 8
Russia has up to eleven time zones beginning from Kaliningrad to Kamchatka Chri with a nine-hour time differential in its time zones.
Several countries the Standard time zones and in some countries have deviations of thirty minutes or more from the standard time.

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