European interest in Indian spices burgeoned during the 15th century, but passage to India was largely controlled by Arab rulers. When da Gama embarked on his second voyage to India, around 1502-1503, he took with him a fleet of 20 ships, including the Esmeralda. The 15th century to the 17th century marked a period of booming European exploration, during which time European nations were fervently searching for maritime routes. By measuring the altitude of the sun at noon, navigators could then measure the sun's declination, which accurately told sailors their latitude. A broken bracket at the top of the disc indicates it was likely suspended to align it perpendicularly to the horizon. By aligning an astrolabe perpendicular to the horizon, ancient astronomers could calculate measurements like time and position.Īstrolabes used by early sea explorers are frequently referred to as mariner's astrolabes. They're one of human civilization's most advanced ancient tools and are thought to have become popular just prior to the current era. Markings on astrolabes are used to measure angles. "The resolution of the 3D data allowed us to zoom in and identify the marks and subsequently characterize them." "The markings were very fine and, due to damage to the surface, almost invisible to the human eye," said Williams. What they saw on the scans wasn't visible to the naked eye-eighteen individual lines emerging from a hole in the center of the disk and arranged at five-degree increments. Using a laser scanner that produces 80,000 measurement points per second, they were able to create a 3D model of the astrolabe. They flew to Oman to scan and render 3D images of the 500-year-old artifact. That's where Mark Williams, a professor at the University of Warwick, and a team of engineers came in. While these markings suggested that the disk was used for navigation, Mearns and his team needed more proof before they could declare it with certainty. These etchings indicated to archeologists that the object was a "high-status" object aboard the Esmeralda. In an interim report they published last year on the find in the International Journal of Nautical Archaeology, they theorized that the disk was used for navigation.Ī Portuguese royal coat of arms was visible on the disk's top half, and on the bottom was an etching of an armillary sphere, which Mearns claimed belonged to Portuguese King Dom Miguel. loosened the astrolabe from sand covering hundreds of other relics that sat on the sea floor. Mearns and his company Bluewater Discoveries Ltd. In 2014, a team of excavators led by marine scientist David L. The disk was found on a ship called the Esmeralda, which belonged to a fleet led by the famous Portuguese explorer Vasco da Gama during his search for a route from Europe to India in 1502-1503. It is also now thought to be the earliest such find from a period known as the European Age of Exploration. Now, thanks to 3D scanning technology, scientists are able to see the small faded measurements etched into the disk-which confirm that it is in fact an astrolabe. When a small, 500-year-old copper disk was discovered among the remains of a shipwreck off the coast of Oman in 2014, archaeologists suspected it was a navigation tool called an astrolabe.