The Vikings faced a particular problem: the journey from Norway to Iceland, and then on to Greenland, took place at a constant latitude, very close to the Arctic Circle (shown in red in the image).
However, these voyages took place mainly in the summer, as winter weather conditions were extremely harsh. It was therefore almost never dark, so the North Star could not be used for navigation.
Furthermore, their voyages took place from the 10th to the 15th centuries. They thus began before the introduction of the compass in the West.
So, how did they navigate?
Some archaeologists have suggested that the Vikings may have used a solar compass to find north (and thus west to reach Iceland and then Greenland, and east for the return journey).
If it was almost never dark, that means the Sun was visible practically all the time!
Researchers have built a replica, pictured here.
It consists of a disk about ten centimeters in diameter, with a vertical rod in the center (a gnomon), as well as various markings that resemble the diurnal arcs of a sundial.
Here’s how it works:
- Before you go:
Over the course of one day (at the desired latitude of travel), record the position of the gnomon’s shadow to plot the diurnal arc. The image shows three arcs: at the bottom, the summer solstice; in the middle, the equinox; and at the top (when the shadow is longest), the winter solstice.
- During the trip:
Rotate the disk so that the gnomon’s shadow falls on the drawn diurnal arc. North lies along the axis of the gnomon and the points where the diurnal arc is closest to the gnomon (noon).
First, the archaeological evidence is scant. Here is the discovery on which the idea of a Viking solar compass is based: the Uunartoq disk.
Admittedly, the instrument would have been made of wood or some other brittle material so that it could be engraved or marked, and such materials do not preserve well in the cold, damp environment of the regions where it might have existed.
But although the Vikings did not have a written language (runes are not a writing system capable of conveying the concepts necessary to explain how it worked), they were not isolated. Such a discovery, made before the arrival of the compass, would undoubtedly have been shared and thus known to neighboring peoples.
The mystery remains unsolved!
