Although considered by many to be a ruthless and violent horde, the Vikings have also left behind a few treasures, trinkets, and artifacts which suggest that they were in possession of technologies far beyond what was previously believed.

In the 1990s, on the island of Gotland, Sweden, the excavation of Viking graves turned up a number of pieces of quartz crystal that appeared to have been manufactured into precise shapes.

It was first assumed that these were ornaments until closer examination found that they had been crafted into elliptical lenses and that, as lenses, they performed nearly as well as modern equivalents.

Amongst the weapons, jewelry, and looted treasures that have been recovered from the graves of prominent Vikings, the Visby Lenses are arguably the most astonishing.

Some of the lenses have been treated as jewelry, set in decorative and intricately carved silver mounts, although it is believed that the lenses themselves may be a great deal older than their housings.

The Lenses have been cited as evidence that sophisticated artisan manufacturing techniques were being used more than 1,000 years ago, when the laws of refraction were not yet understood. The precision with which they were made suggests that a primitive turning lathe must have been used.

Some have suggested that the process involved in the making of the lenses may have been a secret shared by just a few master artisans or perhaps held by just one and that all of the Visby Lenses may have been the work of one single pair of hands.

The potential uses for the lenses have been discussed by historians, with various explanations being put forth. Some have suggested that they were used for reading. One researcher stated that, “they could have been used to start fires or to burn wounds and cuts so that they did not get infected.” The most intriguing possible use, however, is as part of a telescope.

If it were the case that the Visby Lenses are indeed elements of what was once a telescope, it would predate the 16th-century Dutch telescope invention by some 500 years...