- In Ptolemy's Geographia (c.150 CE), the Roman Prime Meridian or Zero Degree Longitude, was centred on Mount Teide in Tenerife.
- Mount Teide is located at 16°38′22″W of the Greenwich Prime Meridien.
Mount Teide and not Rome
- The Zero Meridian did not pass through Rome, because shipping in the Ancient World did not yet use negative numbers for Longitude.
- Therefore the Zero Meridian had to start away from the most western point of Africa, so that all navigation could take place with positive numbers of Longitude, from 0 to 360 degrees.
- Today, the Prime Meridian is located in the Royal Observatory, Greenwich, London, England.
The Calculation of Longitude
- Longitude of a city in the Ancient World was calculated by comparing the times of the Lunar Eclipse between cities in various countries.
Roman Sources describing the Canary Islands
- Pliny the Elder (23-79 CE)
- Described an Expedition in 50 BCE to the Fortunate Islands, by Juba II of Mauretania, who appeared to have found the ruins of large buildings, although Pliny does not describe the Guanche.
- Plutarch (46-c.120 CE)
- In his ‘Life of Sertorius’, described two islands in the Atlantic Sea off the coast of Africa called the Fortunate Islands and suggests they must be Elysium. His description of their climate matches that of the Canary Islands.
El Hierro, Canary Islands
- El Hierro is the furthest west of the Canary Islands, and of the ‘Old World’ before the discovery of America in 1492.
- It was used as the Prime Meridian for over 500 years by various European nations, including France from 1634.
- However, the Netherlands used Mount Teide as the Prime Meridian from the 1640’s until 1826.
Roman Prime Meridian, Mount Teide, Tenerife