Phase Zero Hypothesis — The Bull in the Sky: Meskhetyu and the Shemsu Hor Path from Nabta Playa to the Giza Plateau

The First Trilogy established a coherent, evidence-grounded account of Saharan pastoralist migration to the Nile Valley during the collapse of the African Humid Period (~5,500 BCE), the transmission of the Zep Tepi cosmological system via the Highland Corridor Refugia, and the institutional memory carried by the Shemsu Hor. It closed at Hierakonpolis, approximately 500 years before the Great Pyramid. Phase Zero addresses what that interval contains. This paper proposes that seven small, uninscribed step pyramids — the Minor Step Pyramids of el-Kula, Edfu, Hierakonpolis, Naqada, Sinki, Zawyet el-Amwat, and Seila — distributed across the ceremonial centres of Predynastic Upper Egypt, represent a coordinated territorial and cultic programme encoding the Meskhetyu (Ursa Major/Bull's Foreleg) astronomical tradition at precisely the Shemsu Hor sites documented in Paper III. These structures predate or overlap with Sneferu's large pyramid programme and have no burial function. Their shared plan, orientation family, and geographic distribution at Shemsu Hor ceremonial centres are not coincidental. The paper distinguishes two parallel tracks: a territorial track (Minor Step Pyramids encoding Meskhetyu at provincial sites) and a construction-engineering track (Djoser → Sneferu → Khufu, improving precision from ~3° to 3′ of north over five pyramid projects). Both tracks target the same constellation throughout. Seila MSP is the convergence point: simultaneously the last Phase Zero territorial marker and the first of Sneferu's four construction experiments. Section 13 presents a fully transparent three-approach calculation of construction capacity — top-down (blocks ÷ time), bottom-up (workforce capacity with sled physics), and Wedjat cross-check (validating team sizes via binary mechanical advantage) — demonstrating that the active construction effort across the full 3rd–4th Dynasty pyramid programme occupied a modest fraction of the 500-year interval. The remaining centuries were required for the institutional, organisational, and logistical capacity that made Giza possible. Phase Zero closes the capacity question. The purpose question — what that capacity was ultimately for — continues as the subject of The Pyramid as Memory Hypothesis.