How did the viking sunstone work?

Vikings is the modernized name given to the seafaring people from Scandinavia, which is present-day Sweden, Denmark, and Norway. They were a group of expert sailors and navigators and relied on mysterious items, such as the sunstone, to navigate the ocean. In this write-up, we will look deeper into the meaning of the Viking sunstone and its uses.

The Viking Sunstone History and Facts

The Viking sunstone is a unique type of mineral that was valuable to the seafaring people from Scandinavia – the Vikings. It is attested in many 13th-14th century literary sources from Iceland and is also mentioned in several inventories of the church and monasteries around Scandinavia. The sunstones have been found at various Viking archaeological sites and some were uncovered in different shipwrecks.

Long before magnetic compasses were available in Europe, let’s say 1000 years ago, Vikings relied on the sun to determine their heading and to avoid getting lost on their voyages across the North Atlantic sea. On good days, the skies were clear and the sun was easily visible, but there are days when they would sail under a completely overcast sky. During the night, they had to rely on the position of the stars to guide them through their journey, but there are times when there were very few stars in the sky. For this reason, they had to rely on one navigational instrument that seemed the most accurate at the time – the sunstone. It helped them uncover the position/direction of the sun when the sky was completely covered by clouds.

Initially, Vikings made short but hazardous trips across the North Sea to the coasts of Northern England and Scotland. As time went by, they reached North France and Ireland. Later on, they explored Iceland and further south; they conquered greater parts of Northern France and England. To the East, they went to Ukraine, Russia, and the Baltic. Eventually, they found themselves all the way west to Vinland, what is presently called North America. They settled, conquered territories, raided, and traded in each one of these areas. They had no timepiece, sextant, or compass to help them navigate through the seas. So, how exactly did they do it?

There is an Icelandic saga about how the Vikings used the sunstone, known as the ‘Saga of King Olaf the Holy’ by Hrafins. According to this Saga, King Olaf Tryggvason consulted Sigurd and Dagur, who were with him on the ship, to find out the position of the sun during a snowstorm. After Sigurd gave him an answer, King Olaf held out a sunstone to the sky and studied it to affirm Sigurd’s answer. Also, several other stories describe how different mariners during the Viking Age used the sunstone to find their way across the seas towards the Northern hemisphere. They didn’t use it on a daily basis, however. As we mentioned earlier, they only used it to find the sun in a cloud or beyond the horizon during the long twilight hours of the Northern summer. As the Vikings approached areas of confused magnetic deviation, the Viking sunstone was the most reliable guide as it helped them figure out where true north and south were.

Did the Vikings use sunstones as a compass?

Yes, they did. Unique crystals of calcite, such as the Viking sunstone used by Vikings enabled them to seamlessly and successfully navigate very lengthy voyages. Every time the navigators took readings after every 3 hours or less, they had a higher chance of making it to Greenland or their final destination successfully. If they took readings after regular intervals of 4 hours, they had a 50% chance of making it to their final destination, and if they took the readings after about 5-6 hours, chances of making it to their anticipated destination were very low. Well, what could be the explanation behind this?

The Vikings believed that the frequency of readings and using the sunstone for an equal number of afternoon and morning readings were the keys to a successful journey. This was often because morning readings can cause their ship to veer off too far North, and afternoon readings may cause the ship to veer off far South. If they weren’t precise, then they would miss Greenland or any other destination. So, using the sunstone kept them in check at all times. Once they uncovered the direction of the sun, they would look into other essential factors such as their strong sense of time and understanding of wind and current, they were able to easily find their way.

How did the Viking sunstone work?

Generally, Vikings used the transparent calcite crystal, which they referred to as the Viking sunstone or the Iceland spar, to fix the true bearing of the sun. In simpler terms, the sunstone acted as a compass so that they wouldn’t get lost at sea. Also, they would use it in twilight and cloudy conditions to figure out their sense of direction. According to most scientists, researchers, and archaeologists, the naturally occurring sunstone can ‘depolarize’ light, filter it, and fracture it along different axes. That said; let us explain how the Viking sunstone worked.

The navigation process involved moving the stone across the visual field and tracking a yellow entopic pattern using the naked eye. If that didn’t seem to work, they would put a dot on top of the crystal and look at it from below. Two dots would appear because the light is fractured along different axes. Afterward, they would rotate the crystal until the two points have the same darkness level of intensity. At that particular angle, the surface facing the top gave the direction of the sun.

Also, they would do the same in twilight conditions and were able to easily determine with precision the exact direction of the hidden Sun. To add a little more context on the same, the human eye has the ability to seamlessly distinguish between different shades of contrast, hence making it easier to identify when the two dots/spots are truly identical or when they are different.

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