Researchers at the University of Warwick in the United Kingdom believe that the astrolabe recovered off the coast of Oman is the oldest navigation instrument ever discovered.
The ship Esmeralda will have been shipwrecked in the Indian Ocean in 1503 and this was one of two ships of the Vasco da Gama fleet (the other was São Pedro) that is known to have been shipwrecked during the second voyage of the navigator to India.
The remains of the Emerald ship were discovered off the coast of Oman almost two decades ago. What was believed to be the remains, but many archaeologists began by challenging the discovery. Now, after the exact location of the Emerald ship was published last year, another archaeological discovery made shortly before, definitively proves that, whether or not it was the Emerald ship, this was definitely a Portuguese vessel that belonged to the time of the Discoveries.
In 2014, British researcher David Mearns, head of the Blue Water Recoveries, led an expedition to the remains of the ship. And of the nearly three thousand artifacts that Mearns recovered during the expedition, there was a bronze disc 17.5 centimeter in diameter and two millimeters thick. This was an astrolabe, believing the researchers that it is also it, the oldest navigation instrument ever discovered.
“The astrolabe had two symbols that we would identify: one was the Portuguese coat of arms; the other was the personal emblem of D. Manuel I, then King of Portugal”, David Mearns told the BBC. Adding: “We know that it was manufactured before 1502 because that was the year the ship [Esmeralda] left Lisbon. And King D. Manuel only ascended the throne in 1495 – this astrolabe would not have the emblem of the monarch if he were not yet the king of Portugal. I think it is fair to say that the astrolabe dates from the period 1495 to 1500”.
After recovered during the expedition to Oman, the astrolabe was analyzed in more detail by investigators of the University of Warwick, in the United Kingdom. The bronze disk had no navigational marks. But later, after laser technology, Warwick scientists studying the astrolabe found marks (with five-degree intervals) around the disk. It would definitely be an astrolabe.
It is rare to discover the astrolabes used by navigators of that time: little more than a hundred have been cataloged until today. The head of Blue Water Recoveries knows it. “It’s a great privilege to find something so rare, something so historically important, a breakthrough that is being targeted by the scientific community”, David Mearns told the BBC. The astrolabe was used by navigators to measure the altitude of the Sun in relation to the horizon, to determine the position of other stars in the sky and to enable the location of the vessels, allowing them to know which way to go.
Portugal has not so far been officially informed by the authorities of Oman about the discovery of the Emerald ship. However, this can be considered heritage of the Portuguese State. And the government has already stated its intention to send experts to Oman to investigate the shipwreck of the Emerald ship, awaiting the response from the Omani authorities.