The 24-hour analogue clock
This is the Shepherd Gate Clock, which since 1852 has been installed outside the gates of the Royal Observatory Greenwich. Notice anything strange?
Instead of the usual numbers 1-12 on its clock face, it has 24 Roman numerals. That means that the hour hand goes round only once in every 24 hours.
At 12 noon, instead of pointing straight up, the hour hand points straight down at XII. If you want to confuse your friends, you can own your very own replica version.
But this clock has another secret. The Shepherd Gate Clock was linked to the main 'motor clock' inside the Royal Observatory, which from 1852 to 1893 wasthecentral clock that determined the whole British time system.
By using telegraph wires, the time determined by this highly accurate Observatory clock could be shared across the country. For the first time, cities from London to Glasgow to Belfast could share exactly the same time.
By 1866 Observatory time was even being sent to the United States, with transatlantic submarine cables connecting Greenwich with Harvard University in Massachusetts.
If all this talk about time has got you in a spin, why not visit the Royal Observatoryfor yourself? Explore the home of Greenwich Mean Time, and find out more about the mysteries of space at London's only planetarium.
