Vikings Used "Sun Crystals" to Navigate The Ancient Seas Study Shows . A thousand years ago the trip between Norway and Greenland by longboat took about three weeks. Viking navigators used shadows cast by a sun compass a ring with a central fin like a sun dial's to identify geographic north.
Temple of the Three Windows, Peru — by Christina Adams
Temple of the Three Windows, Peru - Temple of the three windows in Machu Picchu. When the sun shines through the windows, a shadow is cast in front of the stone on the left to complete the Andean cross. #machupicchu #peru