A copper alloy astrolabe found in a shipwreck in Oman dates between 1496 and 1501, making it the oldest mariner’s astrolabe ever discovered.
(Mearns et al., International Journal of Nautical Archaeology, 2019. DOI: 10.1111/1095-9270.12353)
A rare navigational tool has snagged a Guinness World Record as the oldest mariner’s astrolabe.
The astrolabe dates between 1496 and 1501; it sank to the bottom with a shipwreck in 1503 in the vicinity of the coast of the island of Al-Ḥallānīyah, in what is now saudi arabia. The find is one of only 104 historical astrolabes in existence.
“It is a great privilege to find something that is so rare, it is something historically important,” David Mearns, an oceanographer of the Blue Water Recovery, said in 2017 a statement after the astrolabe was first analyzed. Mearns, who led the archaeological excavation of the wreck, added, “It was as if nothing had seen.” [The 25 Most Mysterious Archaeological Finds on Earth]
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Mariner’s astrolabes are round devices that sailors used to measure the height of the sun or the stars, allowing them to calculate their ship’s latitude. The instrument that was just listed in the Guinness book of World Records, was discovered under a layer of sand in the Arabian Sea in 2014. The astrolabe went with a ship under the command of a Portuguese commander with the name Vicente Sodre, who was the uncle of the famous explorer Vasco da Gama.
Sodré and his brother Brás Sodré, were the commander of a subfleet of five ships in the 4th Portuguese India Armada in 1503. The two men were supposed to be patrolling from the south-west of India, to protect a few of the trade outposts. Instead, the commanders went rogue and ran to the Gulf of Aden, where the officers and their men plundered several Arab ships. The brothers went to Al-Ḥallānīyah and stopped to make a few repairs. In May 1503, a huge wind blew in, smashing two of the ships, the Esmeralda and the Sâo Pedro, in the rocks of the island. Vicente Sodré died in the wreck; Brás Sodré also died — on the island — although the historical data do not provide the cause of death.
The disaster was famous because of the ships was loaded with cargo, and left Portugal’s trading posts open for an attack by Indian troops. In 1998, archaeologists examined the area where the ships were supposed to be recessed and found what seemed to be a wreck. It was not until 2013, but that the Oman government and researchers will be able to arrange an excavation in the remote area. The next two years, archaeologists found almost 3000 objects from the site, including a ship’s bell engraved with the year 1498.
Navigation by the stars
The astrolabe was found under 1.3 feet (0.4 meters) from the beach in a natural trench in the vicinity of the wreck. The artifact measures 6.9 inches (17.5 cm) in diameter and is decorated with the Portuguese coat of arms and armillary sphere — a representation of the position of the celestial bodies around the Earth . (The armillary sphere was a common Portuguese emblem, and is still part of the country of the flag.) The metal used in the making of the astrolabe is an alloy made mostly of copper, with a little zinc, tin and lead.
Years of damage by salt water and tide erased most of the other markings on the astrolabe. To discover what there could no longer be seen with the naked eye, researchers at the University of Warwick in England used laser scanning to detect the tiniest grooves and etchings on the disk. Their results are published in the International Journal of Nautical Archaeology, revealed 18 scale marks on the upper right of the disk, which would have allowed the navigator to measure the angle of the sun or the stars.
The first recorded use of an astrolabe was an expedition by a Portuguese explorer in 1481, the researchers wrote, but the earliest versions were probably made of wood and have not survived the centuries. The Sodré astrolabe had to be made before February 1502, when the squadron left Lisbon. The armillary sphere was an emblem of Dom Manuel I, king of Portugal from the end of 1495 to 1521; the astrolabe was probably made during his reign, circa 1496 at the earliest, the researchers concluded. The 1498 ship bell and the dates of coins found in the wreck all of the support that date range, they wrote.
According to the University of Warwick, the ship’s bell will also be taking pride of place in the Guinness book of World Records as the oldest vessel of the clock that has ever been discovered.
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Originally published on Live Science.