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 (~5,300 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 Elephantine, El Ghoneimiya (South Edfu), el-Kula at Hierakonpolis, Naqada, Sinki, Zawiyet el-Mayitin and Seila — distributed across the ceremonial centres of Predynastic Upper and Middle Egypt, represent a coordinated territorial and cultic programme encoding the Meskhetyu (Ursa Major/Bull's Foreleg) astronomical tradition. Five of the seven stand at major Predynastic ceremonial centres, two of them — Hierakonpolis and Abydos — carrying the explicit Shemsu Hor textual associations 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 are proposed here as a coordinated programme rather than a coincidence; the paper states the competing explanation, which reads the same distribution as marking the Old Kingdom's major economic centres, and reframes its central prediction to discriminate between the two. 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 a Wedjat cross-check deriving standardised crew sizes via binary mechanical advantage — with the dependencies between the three stated rather than presented as mutual corroboration. On the shortest defensible reign lengths, the accumulated active construction time across the full 3rd–4th Dynasty pyramid programme falls in the range of approximately 85–110 years. The remaining four centuries of the interval 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.