Vikings were surprisingly well focused

2019-03-08 08:06:05

By Duncan Graham-Rowe STUDIES of Viking lenses suggest their makers could have taught modern optometrists a thing or two. Quartz lenses made around one thousand years ago have optical properties that match modern standards. Aspheric lenses, which have an elliptical shape, are commonly used in spectacles and cameras. The equations describing their optical properties are thought to have been devised by the French philosopher and mathematician René Descartes in the 17th century. But he could not find anyone skilful enough to make one. Yet now it seems the Vikings were making them hundreds of years earlier. Optics specialists led by Olaf Schmidt of the University of Applied Science in Aalen, Germany, have studied Viking lenses from museums in Munich and Sweden. They found their shapes closely matched an ellipse. The optical qualities of some of the best examples were comparable to modern lenses. “If you look at the shape of the lenses they are remarkably smooth,” says Schmidt. Schmidt believes the lenses were made on a simple lathe and used for focusing sunlight to light fires and cauterise wounds. How Viking craftsmen discovered the optimum shape remains a mystery. “I think it’s very unlikely they understood the mathematics of the lenses,” says John Bell,