Overlooking Greenwich with one of the greatest view is the Royal Observatory, the First Observatory of England. It was designed by Sir Christopher Wren and built in 1675. The first Royal Astronomer was John Flamsteed. He was succeeded in 1720 by Edmond Halley, who charted the course of his famous comet here but died before seeing his calculations proved correct. In 1833 a first ball was placed on top of the observatory and since that day the time ball has been raised at 12.55 and dropped at 13.00. so the ships on the river can set their clocks. In 1884 a conference in Washington voted that Greenwich should be the location of the Prime Meridian. There were two reason for this: first, the observatory’s work had been instrumental in calculating the new methods of navigation and time-keeping, second – a large proportion of the world’s shipping at that time passed through the Port of London. Hence East meets West at Greenwich and the world set its clocks by Greenwich Mean Time.
There is a line marking the Prime Meridian and a lots of fun can be had by straddling the line by placing one foot in the Eastern Hemisphere and one foot in the Western Hemisphere. Also there is a laser light at night which shines out from the observatory along the line of the Prime Meridian, which crosses the river near the Blackwall.
The 28 – inch (710 mm) reflecting telescope at Greenwich Observatory is the largest in Britain and the seventh largest in the world.