Astronomy Picture of the Day

Explanation: In the Sahara Desert in Egypt lie the oldest known astronomically aligned stones in the world: Nabta. Over one thousand years before the creation of Stonehenge, local herders built a stone circle and other structures on the shoreline of a lake that has long since dried up. Over 6000 years ago, stone slabs three metres high were dragged over a kilometre to create the site. Shown above is one of the stones that remains. Little is known about the ultimate purpose of Nabta and the nature of the people who built it.