Set your watch by the Greenwich Time Ball

As the clocks go back by an hour, and we return to Greenwich Mean Time, it seems sensible to ensure that today's entry is in Greenwich and is one you can set your watch by. Let us examine, therefore, the Greenwich Time Ball, which sits atop the Observatory and rises half way up its mast at 12.55pm, rising to the top at 12.58pm. Then at 1pm exactly, it falls, as a signal to all the people and ships in the area of the exact time. The ball has been doing this daily since 1833.


It was vital for navigation that all ships carried a timepiece with exact Greenwich Mean Time, as using a sextant you can work out the exact time from the sun wherever you are, and then compare and this to Greenwich Mean Time to work out how far around the world you are. This was the reason that Greenwich Meantime was so important to navigators, so the ball provided a vital service to nearby ships preparing to embark on a long voyage.

For more information on http://www.nmm.ac.uk/places/royal-observatory/time-ball/


_{^Picture from Flickr courtesy of wka^}