A great knowledge of the ways of the sea was passed down by word of mouth from generation to generation of Vikings. And, perhaps they had some technologies now lost.
The Vikings were great sailors. They could live for months at sea off fish supplemented by scant provisions. They didn’t have compasses or sextants. They did have an oral tradition that passed from father to son a great knowledge of geography, prevailing winds at different places at different times of the year, and also great courage. The later is probably the most important element of Viking navigation, to merely reach your destination with ship, crew, and cargo intact was an outstanding feat. The risks were great, but so were the rewards in wealth and fame for your family. The whole Viking worldview and attitude towards living developed in their bleak cold northern homes made them specially suited for the risks and rewards of sea voyaging.
In addition to a great store of sea knowledge passed down through the generations, and the Vikings also had a few other tricks up their sleeves. One chronicle relates how Floki Vilgerdarson found Iceland by carrying three ravens aboard his longboat. One was released and flew back towards home, a second was released, and perched on the mast refusing to take flight, but the third, when released, pointed the way to Iceland.
In the Vikings home waters of the relatively shallow Baltic Sea sounding (i.e. measuring the depth of the waters) has long been a useful navigation tool for those who know how deep the water is at given places. It is very likely that the Vikings sometimes employed this method.
Stone artifacts have been found bearing scratches that can be used to stay on a certain latitude at different times of the day by reading shadows cast on them. Also knowledge of types of seabirds, seaweed, and other flotsam could inform them of their position relative to land known or unknown, and their ancestral knowledge included a great deal about finding your location by the sun and the stars. However in the far north, the sun is often below the horizon during most of the day, Viking voyages to Iceland, Greenland, and America were almost certainly under such conditions, and often in storms or deep fog. How did they find their way when the sun and stars could not be seen? Several sagas mention a device called a sunstone.
The sunstone is mentioned with reverence and undertones that have made it seem magical and legendary. Many today still believe that it is purely a myth. Others speculate that it was a natural crystal which could refract light, making it possible to see the sun when it is not otherwise visible. Bees and ants use refraction of light to find directions. Did the Vikings do the same? Some modern night compasses work on this principle. Was the sunstone a magical myth like Thor’s hammer, or a simple natural crystal through which the sun could be seen by refraction? Unless one is found in a wreck or byre, we will likely never be sure, but I for one find the theory very plausible.
The facts are indisputable on one thing. The Vikings were the greatest sailors of their time, and their longboats and skills carried them further than any other traveler of the Dark Ages.
Lief Ericson discovered America
