The Great Pyramid's Southern Shafts and the Noon Sun: A Reproducible Calculation

The south-directed shafts of the King’s and Queen’s Chambers in the Great Pyramid lie approximately in the meridian plane, which the Sun crosses at local noon. Whereas previous research has focused on their possible stellar targets, mainly Orion’s Belt and Sirius, this study asks on which dates the Sun’s noon altitude at Giza equaled the shaft inclinations. Using published shaft measurements and the JPL DE422 ephemeris, it computes the dates on which the Sun’s airless meridian altitude equals the adopted inclinations of 45.00◦ (King’s Chamber) and 39.6078◦ (Queen’s Chamber). For 2550–2549 BCE, close to the conventional construction date of the Great Pyramid, these altitudes occur about 50 days (King’s Chamber) and 31 days (Queen’s Chamber) before and after the winter solstice: 21 November and 1 March for the King’s Chamber, and 10 December and 10 February for the Queen’s Chamber (proleptic Julian). These paired dates follow from the annual cycle of solar declination and are not, by themselves, evidence of design. In a second step, the sky near local midnight is computed for each of the four solar dates (two per shaft), and the positions of Orion’s Belt, Sirius, and all 93 Hipparcos stars brighter than V = 2.5 are compared with an idealized due-south shaft direction. On the November date, Alnilam lies 0.025◦ from the King’s Chamber direction, and on the December date, Sirius lies 0.554◦ from the Queen’s Chamber direction; each is the closest star in the search. On the February and March dates, no star in the sample lies within 3.7◦. These stellar separations change by several tenths of a degree per century because of precession, and all results are conditional on the adopted inclinations, epoch, and idealized shaft geometry. They do not imply any historical or architectural intention.