A bronze artefact recovered from the wreck of an India-bound spice ship has been confirmed as the world’s oldest astrolabe – a type of marine navigation tool.
The piece was discovered in 2014 when divers from West Sussex-based Blue Water Recoveries excavated the wreck of Portuguese explorer ship the Esmeralda. The vessel, which sank to the bottom the Indian Ocean during a storm in 1503, was part of a fleet led by Portuguese explorer Vasco da Gama, the first person to sail directly from Europe to India.
Experts believed the bronze object was an astrolabe – a tool that allowed mariners to measure the height of the sun above the horizon at noon to determine their location. However, no navigational markings were visible. It was only when scientists from the University of Warwick were called in to investigate did the full picture become clear.
The university team used pioneering scanning technology to reveal the artefact’s invisible details. They found etches around the edge of the bronze disc, each separated by five degrees, proving it was indeed an astrolabe cast between 1495 and 1500.
Professor Mark Williams from WMG at the University of Warwick, said: “It was fantastic to apply our 3D scanning technology to such an exciting project and help with the identification of such a rare and fascinating item.
“Usually we are working on engineering-related challenges, so to be able to take our expertise and transfer that to something totally different and so historically significant was a really interesting opportunity.”
The technology was able to accurately scan the item to within 0.1mm, allowing the British team to reproduce a high-resolution 3D model. The astrolabe is engraved with the Portuguese coat of arms and the personal emblem of Don Manuel I, the King of Portugal between 1495-1521.
David Mearns, part of the team from Blue Water Recoveries which led the 2014 excavation, added: “It’s a great privilege to find something so rare, something so historically important, something that will be studied by the archaeological community and fills in a gap.”