On the 27th June, 2016, I, along with my cousin, took a trip to the Royal Observatory at Greenwich, with a visit to its Planetarium. The Observatory’s “learning focus” is of coursed based on its history – it was a base for the study of stars for centuries and a residency for many high profile astronomers who worked there, e.g. John Flamsteed, who is thought to be the first astronomer to take sight of Uranus. Notably, the Observatory also houses the Prime Meridian, and is the origin of GMT – Greenwich Mean Time.
John Flamsteed was the first ‘Astronomer Royal’ to live in the Observatory. Handpicked by King Charles II, the commissioner of the Observatory, his work involved documenting the stars in order to advance navigation.
Britain relied heavily on trade and colonisation, and sailors used the North star to work out how far north or south they were. However, technology was not appropriate enough to work out how far east or west they were, and this proved to be hindering their progress. Two methods were created to solve this longitudinal issue: the lunar distance method or the time method.
The Octagon Room
A room that stood out to me during this visit was the Octagon Room. Designed by the same architect who created St Paul’s Cathedral, Sir Christopher Wren, the windows are 13 feet high. The reason for this was so that long telescopes would be able to fit that had the purpose of observing eclipses, comets and other celestial events. However, this could not occur due to the unfortunate positioning of Flamsteed House itself – as a result, many observations were taken in an outhouse located in the Observatory’s gardens.
Some timepieces and instruments were on display in the Octagon Room – for example, the Sidereal Angle Clock, that was designed by John Flamsteed. Instead of giving the time in the now common hours, minutes and seconds, it gave it in the rotation of the Earth – angles. Thus, it relied on the Earth’s rate of rotation in regards to the fixed positions of the stars – any star other than the Sun, because to the naked eye, they do not appear to move. It was not practical in long term application as a result of this. Also on display was a lifesize model of the telescopes that would have commonly been used in the Octagon Room – though rendered useless, as mentioned earlier – and it projected a small image of Saturn as you looked through it, as an example of what you would have seen if the position of Flamsteed House had been according to a Meridian.
What is a Meridian?
Meridians are reference points that sailors would use to help navigate the seas, and that astronomers use to help with their observations of the sky. The Prime Meridian is located at a longitude of 0°, and it was also decided to be held at Greenwich simply due to political convenience & popularity – the large colonial powers of Britain at the time, and the part the country had played in the technological advancements of seafare meant that at the International Meridian Conference of 1884, the decision was overwhelmingly in England’s favour. France abstained from this vote and continued to work under the Paris Meridian until 1911.
How is it related to the GMT?
The Prime Meridian was also used to create the GMT that all countries now follow today in order to maintain the time and date in their respective lands – each 15° east or west from Meridian (0° Longitude) represents an hour. 15° east of Greenwich is an hour forward, whilst 15° west of Greenwich is an hour backwards.