Greenwich Mean Time

Keeping track of time helps us make sense of our world. Read all about the history of timekeeping and the story the Prime Meridian, and discover why Greenwich is known as 'the home of time'.

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Visit the home of Greenwich Mean Time and discover how time-keeping, astronomy, global exploration and world communications are all intricately linked.

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The story of Astronomer Royal George Biddell Airy and the remarkable Airy Transit Circle telescope he designed at the Royal Observatory Greenwich.

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Meridian astronomy is the meticulous surveying of the stars so that positions and movements of stars can be known accurately.

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Why was Greenwich chosen as the home of the Prime Meridian and Greenwich Mean Time, and what do those terms mean?

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How do you know that your watch, clock or phone is telling exactly the right time? At one time, the only way was to look to the roof of the Observatory.

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Astronomer George Biddell Airy designed the legendary Airy Transit Circle telescope which defined the Prime Meridian at the Royal Observatory Greenwich.

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The Royal Observatory Greenwich is the home of Greenwich Mean Time (GMT). But what is GMT and why is it so important?