The slab is marked with round divots arranged in a circle, and an astronomical analysis suggests that these markings coincide with heavenly events, including sunrises and moonrises.
The sundial might be “evidence of attempts of ancient researchers to understand patterns of apparent motion of luminaries and the nature of time,” study researcher Larisa Vodolazhskaya of the Archaeoastronomical Research Center at Southern Federal University in Russia told Live Science in an email.
Last year, Vodolazhskaya and her colleagues analyzed a different Bronze Age sundial, this one found in Ukraine, and discovered it to be a sophisticated instrument for measuring the hours. The work caught the eye of archaeologists in Rostov, Russia, who knew of a similar-looking artifact found in that area in 1991. That slab had been sitting in a museum in Rostov ever since its discovery, and had never been thoroughly studied.
The Rostov slab was found over the grave of a man of about 50, and dates back to the 12th century B.C., similar in age to the one found in Ukraine. Sundials from this era have also been discovered in ancient Egypt, including in the tomb of the pharaoh Seti I.
By studying the geometry of the Rostov slab, Vodolazhskaya and her colleagues discovered that the carved circles, which are arranged in a pattern spanning about 0.9 feet (0.3 meters) in diameter, correspond with the sunrises at equinoxes(days of the year when night and day are equal in length) and solstices (days of the year when day or night are at their longest).
And the Bronze Age people who created the sundial weren’t only interested in the sun. The circles that didn’t correspond to solar movements were linked to lunar wanderings. Because of the angle of the moon’s orbit, our lone satellite goes through an 18.6-year cycle. During this cycle, when it rises, its position shifts from southerly to northerly, and its movements across the sky are relatively high and low. The Rostov slab tracks these movements with circular carvings indicating the southernmost and northernmost moonrises of these “low” and “high” moons.