Chapter 11: The Calibration Anchor: mn Sets the Scale

The neutron is not merely the first particle—it is the calibration anchor. Its mass m_n is the one measurement from which all other quantities in Category τ follow. This chapter establishes the τ-natural unit system: M = m_n, L = ℏ/(m_n c), T = L/c, and remarkably ℏ_τ = 1/4. No SI conversion is performed here—that belongs to Book V. Everything is τ-internal.