From Al Ahram Weekly – Link to original article

Assem Deif investigates the face angle of Egypt’s pyramids. Although it relies on the culmination of Sirius, the brightest star in the sky, it is rounded to match the nearest Egyptian unit, seqed

When the Egyptians witnessed the rising of Sirius just before dawn (known as the heliacal rising), they knew that the Nile would soon flood; for they depended upon the flooding for the agriculture and fertility of their land. The heliacal rising, which falls close to the summer solstice, marked the beginning of the New Year coinciding with the month of Thoth.

Since Sirius brought prosperity to Egypt, tracing of the star was crucial. At the Isis-Hathor Temple of Denderah there is a statue of Isis which was oriented to the rising of Sirius. When the priests saw the rays from Sirius penetrating the temple to fall upon the gemstone she wore, they announced that a New Year had begun. In the temple appears the inscription, “Her majesty Isis shines into the temple on New Year’s Day, and she mingles her light with that of her father on the horizon.”

Sirius did not only bless the living by bringing wealth to the Egyptians, but it also blessed their dead. It was believed that Sirius was the doorway to the afterlife, so the ancient Egyptians abstained from burying their dead at the time of the year when the star was hidden from view, which lasted about 70 days. This led Herodotus to assume that the mummification process could take up to 70 days, yet it is commonly known that it used to last 40 days. Presumably, what he meant was that it would not take more than 70 days, as burying the deceased involved other rituals as well.

The Egyptians, being blessed by Sirius, buried their dead such that the head lay in the direction of the star’s culmination point. In other words, the corpse lay on the meridian with the head pointing due south. Visitors to the King’s Chamber in the Great Pyramid will notice that the sarcophagus is fixed in this direction.

Something for the mathematically gifted amongst you, an examination of the Great Pyramid of Khufu, investigating the possibility that the overall angle of inclination may have been linked to the rise of Sothis/Sopdet, first proposed by Mahmud Hamdy Pacha. Although I find Petrie’s view interesting too, that the “ventilation” shafts had solar connections, being intended to direct the rays of the sun rather than star.