Vikings Navigated With Translucent Crystals?
Icelandic spar may have revealed sun's position on cloudy days, study says.
In some Icelandic sagas—embellished stories of Viking life—sailors relied on so-called sunstones to locate the sun's position and steer their ships on cloudy days. (See Iceland photos submitted by readers like you.)
The stone would've worked by detecting a property of sunlight called polarization.
Polarization is when light—which normally radiates randomly from its source—encounters something, such as a shiny surface or fog, that causes the rays to assume a particular orientation.
Due to this property, as sunlight moves through the atmosphere, the resulting polarization gives away the direction of the original source of the light.
Detecting light's polarization is a natural ability of some animals, such as bees. (See "'Weird Beastie' Shrimp Have Super-Vision.")