Thames Pathway

Journal of a Walk Down the River Thames

by Keith Pauling


Before leaving this part of Greenwich it is time to talk about... time.

The Greenwich Observatory was founded by Charles II in 1675. It was the first building in Britain to be purpose built for scientific research. The first Astronomer Royal was John Flamsteed.

The observatory was set up for a specific reason. In order that the ships of the English Navy would be able to exactly locate position on the ocean it was vital to measure longitude. This is not easy. Latitude was easy, it could be done by measuring the angle of the sun, but longitude was an entirely different matter. To measure longitude required knowing the time at a fixed meridian, and also the exact local time. For this reason ships carried two clocks, one set at a fixed time for a specific meridian and the other was changed as the ship moved. Quickly one moves into matters of definition, not least of which is where a fixed meridian should be, and what the time is at any instant on that meridian. It was first proposed that the meridian should be fixed at Greenwich in 1833.

A conference held in Washington DC in 1884 revealed that 72% of the world’s shipping used Greenwich, and 28% used various others around the world. Again it was suggested that the best answer was Greenwich and nearly every nation agreed but one. Can you guess which one?

Inevitably it was the French. They wanted to use the well known maritime location of Paris. Anyone who has read “The Da Vinci Code” will know that there is a meridian line in Paris, and the French did not want to change it for Greenwich. They did offer to accept it on the condition that Britain adopted the metric system and gave up miles, but they did not expect us to agree. Although they bowed to the inevitable eventually, it was not until 1978 that they gave their official approval.

So Greenwich became the undisputed centre of time and the meridian is marked in several places around the borough.

There is a last piece of time that is worthy of note, the Greenwich Time Ball. This is situated on a pole at the top of the Flamsteed Building and has been used since 1833 to signal time to the ships on the river. Every day, at precisely 12.55 the bright red ball is raised to halfway up the mast. At 12.58 it is raised to the top, and at precisely 13.00 it is dropped to the base of the pole. It is lovely to see that in this digital age it is still in daily use.

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