Monday, 12 July 2010

Royal Observatory, Greenwich

The Royal Observatory in Greenwich is the home of Greenwich Mean Time (GMT) and the Prime Meridian of the world.

The jewel of their collection, at least for me, was Harrison's 1759 prize-winning longitude watch called H4 (for his fourth watch). H1, H2 (was out for conservation work) H3 and H4 were all on display here.  There is an interactive display that reminds me of the British Library's Turning the Pages digitization of objects for a closer look. Also on display was Harrison's Regulator that only lost one second in 100 days.  His closest competition lost 1 second per seven days!  After reading Dava Sobel's Longitude this was a highlight to experience since I did not go here last year.  

The Time Ball

This is the Flamsteed House, the original Observatory building at Greenwich. Designed by (guess who) Sir Christopher Wren and Robert Hooke, it was built in 1676 for the first Astronomer Royal, John Flamsteed.  The ball on top was first used in 1833 to tell time for ships on the Thames.  At 12:55 the ball begins to rise, and falls at exactly 13:00.

 I'm on one side of the hemisphere. Now I'm on the other!  Every location is measured in terms of its distance east or west from this line.

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