The length of the grooves, found on thousands of stones on the island of Gotland, varies from about 0.5 to 1 metre. They are between 5 cm to 10 cm wide and 1 cm to 10 cm in depth.They are shaped as though they were made by a tool fixed on a pendulum, the cross section of the length of each mark being in most cases part of a circle. The most important feature of the grooves is alignment. A study of 1256 grooves showed that they are aligned with certain positions of the celestial bodies, apparently the sun or the moon.Learn More»