The Economist have just published a letter I wrote to them regarding a recent academic article on Viking sunstones.
In the following letter I put forward what I believe to be an original argument on this popular subject. I have no way of proving this theory, which puts me in good company with the scientists who like to come up with new theories on this topic on an almost annual basis. I do at least know what it feels like to hear salt and ice fall from my beard, which may mark it as a little different.
The Viking’s use of sunstones has captured the imagination of scientists more frequently than these stones may have been used practically at sea (“Crystal Gazing”, March 9th).
There are good reasons why sunstones are unlikely navigation aids, and equally good ones why they may still have been carried on ships.
Direct sunlight is not polarised; it is sunlight that has been reflected, refracted or scattered (hence polarised sunglasses are effective at screening out glare when sailing or skiing). In practice polarised light comes from a very different part of the sky to the sun itself, typically a wide band perpendicular to the sun.
I cannot envisage a situation where a sunstone would do a good job. However, sunstones may have been carried by Viking navigators for a different reason. Just as successful generals need their troops to believe they possess extraordinary skills, so navigators in the age before the compass needed sailors to believe they too had skills that went well beyond the normal.
My belief, formed in the North Atlantic and not the laboratory, is that the Vikings relied on the many clues in nature, including the sun and birds, to navigate effectively (see my recent paper, “Nature’s Radar“, for the Royal Institute of Navigation). They may have relied on the sunstone and other legendary routines and rituals to get people to follow them confidently in difficult conditions.
We really appreciate Tristan Gooley’s comments and observations. We totally agree with the Tristan’s comments. There are arguments that birds use polarised light to navigate with. I also do not agree with this idea. It is too complicated, especially with the sun around.