The Astronomical Orientation of the Great Pyramid
The Pyramid of Cheops and that of Sneferu are constructed on a common geometrical plan. The perimeter of the four sides, which face exactly the north, south, east, and west, has the same ratio to the height as the ratio of the circumference to the radius of a circle, i.e. 2 x 3 1/7, or 2π. According to Flinders Petrie: "The squareness and level of the base is brilliantly true, the average error being less than a ten-thousandth of the side in equality, squareness, and level." At its transit across the meridian, the rays of Sirius, the dog star, whose heliacal rising announced the beginning of the Egyptian year and the flooding of the sacred river which brought prosperity to the cultivators, were at right angles to the south face of the Great Pyramid, and shone straight down the ventilating shaft into the royal chamber, illuminating the head of the dead Pharaoh. The main opening, and a second shaft leading to the lower chamber, conveyed the light of the Pole Star, which was then the star a in the constellation Draco, at its lower transit, three degrees below the true celestial pole.