Astronomer Suggests Method by Which Pyramids Were Aligned

A British astronomer may have figured out how the ancient Egyptians were able to align the pyramids in a north-south direction, and she has devised a way to date their construction. There was no north polar star when the pyramids were built, about 4,500 years ago, to guide their construction.

Kate Spence of the University of Cambridge proposes in today’s Nature that Egyptian surveyors used two stars: beta-Ursae Minoris in the Little Dipper and epsilon-Ursae Majoris in the Big Dipper. In 2467 BC, a plumb bob aligned with both stars would point directly north. Before and after that date, the bob would point slightly east or west of north. Using those deviations, Spencer was able to date the construction of each pyramid within 10 years. Construction on the Great Pyramid at Giza, for example, probably began between 2485 and 2475 BC, she said.

--Compiled by Times medical writer Thomas H. Maugh II