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@ Gardening for the Apocalypse
2025-03-19 21:27:07The Vikings, renowned for their seafaring prowess, dominated the seas of Northern Europe from the late 8th to the early 11th century.
These fearless explorers ventured across vast oceans, reaching as far as North America, long before the age of modern navigation tools and centuries before the magnetic compass came to Europe. While their shipbuilding skills and knowledge of the stars were exceptional for their time, one of their most intriguing navigational aids was the mythical "sunstone."
This mysterious tool, steeped in both legend and science, is believed to have allowed Viking navigators to locate the sun even on cloudy days, ensuring they could maintain their course across the treacherous North Atlantic ocean.
The Challenge of Viking Navigation
Navigating the open sea in the Viking Age was no small feat. The North Atlantic, with its unpredictable weather, frequent fog, and overcast skies, posed significant challenges.
Traditional methods of navigation relied heavily on the sun and stars, but in a region where the sun could disappear behind clouds for days, the Vikings needed a reliable way to stay oriented.While they were adept at reading natural signs such as the flight patterns of birds, the color of the sea, and the direction of the wind, the sunstone offered a more precise solution.
Historical accounts hint at the use of a "sunstone" by Viking navigators. One passage even describes a Viking king using a special stone to locate the sun’s position during a snowstorm. For centuries, this reference was dismissed as myth, but modern science has shed light on how such a tool could have worked, reviving interest in this ancient technique.
What Was the Sunstone?
The sunstone is believed to have been a naturally occurring crystal, most likely a type of calcite known as Iceland spar. Another candidate is tourmaline, which exhibits similar optical properties.
These crystals have a unique quality called birefringence, or double refraction, which causes them to split light into two polarized beams. When viewed through the crystal, the light’s polarization reveals patterns that can indicate the sun’s position, even when it’s obscured by clouds or fog.
The key to the sunstone’s effectiveness lies in the polarization of sunlight. As sunlight scatters through the atmosphere, it becomes polarized, creating an invisible pattern that radiates outward from the sun.
By rotating the sunstone and observing changes in the light passing through it, a skilled navigator could detect this pattern and pinpoint the sun’s location, regardless of whether it was visible to the naked eye.How the Vikings Used the Sunstone
To use the sunstone, a Viking navigator would hold the crystal up to the sky and rotate it until the polarized light formed a specific pattern (often a brightening or darkening effect), depending on the stone.
Iceland spar, for instance, produces two distinct beams of light, and when these beams appear equally bright, the crystal is aligned with the sun’s position.
By marking this direction and combining it with their knowledge of time and the sun’s daily arc, the Vikings could determine their heading with remarkable accuracy.
This method was particularly useful during the long voyages across the North Atlantic, where overcast skies were common.
It complemented other techniques, such as using a sun compass, which was a wooden disk with a central pin that cast a shadow to indicate direction when the sun was visible.
On cloudy days, when the sun compass was useless, the sunstone stepped in as a critical backup.
Let's Build One
If you are anything like me, you don't have lumps of Iceland spar or tourmaline crystals laying about your back yard. So I decided to make one using modern materials.
Since the original crystals relied on polarization to achieve their effect, I ordered some linear polarized plastic film online which science teachers often use in classroom demonstrations.
Now the challenge became turning the linear polarization into radial polarization, and I chose to make an octagon out of suitably arranged triangles cut from the sheet.
The image below shows how I created a template on a scrap piece of paper, and then used that to cut triangles from a strip of the polarizing film.
The next step involves carefully placing the triangles onto some clear packing tape so that they stick into place.
I then carefully placed another piece of clear packing tape on top so that the octagon of triangles is permanently fastened into place.
Then with a blade, I trimmed the excess packing tape and the sunstone is complete.
Now to test it!
You can see here that I'm holding the sunstone up against a North facing window so that you can see how the different triangles make different colors depending on their angle to the incoming light from outside.
The light gray triangles indicate the direction of the sun even though the sun is behind the house. and it will work the same way on a cloudy day no matter which way you are facing.
Today, the sunstone captivates historians, scientists, and enthusiasts alike. It’s a reminder that ancient technologies, though simple by modern standards, were often remarkably effective.
The Vikings’ ability to traverse oceans with nothing more than a crystal and their wits speaks to their extraordinary skill.
The earth's magnetic field is rapidly weakening and the poles moving. There may come a day in the not too distant future where navigation by GPS or compass will not longer be possible.
The sunstone stands as a symbol of human curiosity and resilience, which may once again illuminate the path of those who dare to sail beyond the horizon.