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This Sunday, October 29, the UK will adjust slotxo the time backward 1 hour to prepare for winter. Switching to Greenwich Mean Time or GMT (Greenwich Mean Time) makes the UK time 7 hours slower than Thailand.

Greenwich Mean Time, or GMT, is based on the Shepherd Gate Clock at the entrance to the Observatory in Greenwich, south east London. It is a time value calculated from the average time the sun crosses the primal meridian and reaches its peak at noon in a year.

The Big Ben bell will ring again next month. But the clock may not be running correctly.
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What is the primary meridian and how is it important to tell time?

The meridian is a fictitious line that extends from the North Pole to the South Pole. It is an astronomical concept to help determine the position of the stars. The primary meridian has a value of 0 degrees longitude, and every 15 degrees longitude has a time difference of 1 hour.

In 1675 Charles II bestowed part of his land on a hilltop in Greenwich, south east of London. to build the country's first observatory England began to determine the Greenwich meridian from 1675 until around the middle of the 19th century, many countries began to define their own meridians, causing confusion as to which meridian to use as the main one. In October 1884, a meeting was held in Washington, D.C. to set the meridians to be the same standard throughout the world The results of the meeting concluded that the Greenwich meridian was the world's first meridian. Because it is widely known and has been published in the nautical calendar before.

degrees of different cities
Image source,BBCTHAI
Today, the first meridian at the Greenwich Observatory is part of the Greenwich Museum. which is one of the major tourist spots in England There are approximately 8 hundred thousand tourists visiting each year.

Get to know Greenwich Mean Time

During the 15th century, navigation began to be widely used. England was one of the first countries to develop a timekeeping device at sea. leading to the invention of the nautical calendar in 1767

Dr. Lewis Devoy, Curator at the Greenwich Observatory said: People originally counted the time the sun crossed the primary meridian as the point of noon. During the 17th century, astronomers at the observatory observed the time the sun crossed the primary meridian for a period of time. and found that the sun does not always cross the primary meridian at noon And may differ up to 16 minutes because the Earth's axis is tilted and the Earth's orbit is elliptical around the Sun. inconsistent speed So they figured out how to determine the middle time of noon for each day of the year, known as Greenwich Mean Time. and set the Shepherd Gate clock in front of the observatory entrance to London's local time.