Experts from the Guinness Book of Records have confirmed a find to be the world’s oldest mariner’s astrolabe, a navigation device used by seamen in the past. The instrument, known as the Sodré astrolabe was discovered by marine archaeologists in the Indian Ocean and it dates to the very beginning of the 16 th century. As a result of the certification, the mariner’s navigation piece is going to be entered into the next edition of the Guinness Book of Records.

The astrolabe is a bronze disc, which measures 17.5cm in diameter (Image: Philip Koch)

The Marine Tool That Opened Up the World

An astrolabe measures the altitude above the horizon of the sun or the stars and can calculate local time and latitude, fairly accurately. This was main navigation instrument for mariners until it was replaced by the sextant in the 18 th century. They played a very important role in the Age of Discovery when Europeans explored much of the globe - which ultimately led to the emergence of European Empires around the world. The Daily Telegraph reports “they were first used at sea on a Portuguese voyage down the west coast of Africa in 1481”. Astrolabes have also been used by astronomers since the classical era.

This astrolabe is a solid disk device of which there are only approximately 100 specimens in the world. It was recovered by David Mearns of Blue Water Recoveries Ltd and his team of marine archaeologists reports the Ars Tecnia . Mears and his team are world-renowned and they were involved in the exploration of the famous German battleship, the Bismarck, which was sunk during WWII.

Underwater excavations of the Esmeralda. ( Oman’s Ministry of Heritage & Culture (MHC) and Blue Water Recoveries Ltd )

The Wreck of the Esmerelda

The Sodré astrolabe was recovered from the wreck of a Portuguese ship in the Gulf of Oman in 2014. The discovery of the instrument was made near the wreck of the Esmerelda which sunk in 1503. This vessel was part of the second armada of Vasco De Gama (1502-3) a punitive expedition to India, and it sank during a storm. The Esmerelda was commanded by the uncle of De Gama - Vicente Sodré after whom the device is named. Mears and his team also recovered over 1000 items from the site of the wreck, including a bell which was forged in 1498, meaning that it is the oldest example of a ship’s bell in the world.

The bronze ship’s bell has now been confirmed the World’s oldest. ( Oman’s Ministry of Heritage & Culture (MHC) and Blue Water Recoveries Ltd )

The astrolabe is marked with the Portuguese Royal Coat of Arms and also has the personal insignia of King Manuel I (1469-1521) who played a very important role in the Age of Discovery and the establishment of the Portuguese Empire. However, there are no other marks on the disk that could have dated it. The astrolabe is distinctive as it is a “transitional instrument between the classic planispheric astrolabe and the open-wheel type astrolabe that came into use sometime before 1517” according to Phys.org. It is 7 inches thick (15 cm), weighs some 350 grams and its outer case is somewhat corroded.

Scan of the astrolabe artifact, displaying the etches. (Image: University of Warwick )

The Dating of the Sodre Astrolabe

It was not possible for experts to open the instrument to investigate it and to find evidence that would definitively establish its date. A team from the University of Warwick was invited to examine the instrument using 3-D imaging in Oman. Using a small but powerful 3-D scanner the researchers developed a model of the device. Scans revealed that the astrolabe was marked with eighteen spaces that were used to measure degrees. This was important as it allowed the experts to date the item to the early sixteenth century which makes it the oldest surviving example in the world.

18 marks measuring degrees are on the astrolabe. (Image: University of Warwick )

The research has been authenticated by the Records Management team from the Book of Guinness World Records after a long application process. The Sodre astrolabe will be entered into the popular book as the world’s oldest mariner astrolabe. It is important to remember that it is not the world’s oldest example of this type of instrument as this distinction belongs to an astronomer astrolabe. This find is very significant for historians as it can help them to understand the technology that enabled the Age of Discovery that transformed the world and ultimately led to globalization.

Top image: The World’s oldest astrolabe was found in the wreck of the Esmeralda in the Indian Ocean. Source: Youtube Screenshot / Esmeralda Shipwreck

By Ed Whelan