Today in the history of astronomy, celebrations at Stonehenge mark the summer solstice.
Stonehenge has been the site of summer solstice celebrations for millenia. Credit: Andrew Dunn/Wikimedia
Stonehenge, the infamous stone circle on Salisbury Plain, U.K., dates to around 2500 B.C.E. The monument is aligned so that if you are standing at the center of the ring on the summer soltice (which can be June 20, 21, or 22), the Sun rises over the Heel Stone; solstice celebrations are believed to have occurred there for millennia. In the 1960s, Boston University astronomer Gerald Hawkins hypothesized it was a sophisticated astronomical observatory used to predict eclipses. A few years later, Alexander Thom, a retired Oxford professor of engineering, claimed a mind-boggling level of astronomical precision in over 900 stone circles across the British Isles. While these more extreme ideas have been rejected by archaeologists and its precise astronomical purpose remains debated, today the circle is largely accepted to be a method of tracking the Sun and Moon – albeit less precisely that Hawkins and Thom claimed. Newer theories suggest functioned as an ancient solar calendar, possibly for ritual or agricultural purposes. Thousands still gather at Stonehenge to celebrate the summer solstice.
