Icosahedral Group I_h: Order 120, Rotational Subgroup A_5, and Golden Ratio Link — E8 Intelligence Research

FINDING: Icosahedral group \( I_h \) is the full symmetry group of the icosahedron; its rotational subgroup \( A_5 \) is simple, and the group order is 120. | MATH: \( |I_h| = 120 \); rotational subgroup \( I A_5 \), order 60, simple. Conjugacy classes: 1, 12C₅, 12C₅², 20C₃, 15C₂. | CONNECTION: Icosahedral symmetry is the largest of the three full polyhedral groups (tetrahedral, octahedral, icosahedral) and is intimately linked to the golden ratio \( φ = (1+√5)/2 ≈ 1.618 \), its inverse \( φ⁻¹ ≈ 0.618 \), and \( φ^2 ≈ 2.618 \). The coordinates of an icosahedron involve \( 0, ±1, ±φ \). The group is a finite subgroup of \( SO(3) \) and corresponds to the \( H_3 \) Coxeter group, a crystallographic root system in 3D (though not a lattice in Euclidean 3-space, it is a root system for the non-crystallographic Coxeter group \( H_3 \)). | DEPTH: 9 — The icosahedral group is a profound link between geometry, group theory, and number Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com