The oldest mariner's astrolabe yields to scientific scrutiny

THESE pictures are of the plate of a mariner's astrolabe, the earliest known, which was raised in 2014 from a wreck off the coast of Oman. The complete instrument would also have had a rotating pointer, called an alidade, mounted on a pin running through the central hole. The plate itself is 17.5cm in diameter, but less than 2mm thick, and has recently been examined by scanning with a laser beam, by Mark Williams of the University of Warwick, in Britain. Dr Williams used the laser to create a hi...