Each of the three helical ribbons is one Standard Model gauge coupling — U(1)Y (GUT-normalized, blue), SU(2)L weak (green) and SU(3)C strong (red) — traced as a function of energy scale E using the one-loop renormalization-group equation. Height is log₁₀(E/GeV); the radius of each ribbon from the central axis is its inverse coupling 1/αi(E). At the bottom (~91 GeV, the Z boson mass) the three start far apart: the strong force is genuinely strong (small 1/α₃) and the electroweak couplings are comparatively weak. As you raise the energy scale, asymptotic freedom shrinks 1/α₃ upward while the electroweak couplings evolve the other way — the three ribbons twist toward (or away from) each other.
1/α_i(E) = 1/α_i(M_Z) − (b_i / 2π)·ln(E/M_Z)
b_i (SM) = ( 4.10, −3.17, −7.00 )
b_i (+SUSY)= ( 6.60, 1.00, −3.00 )
With plain Standard Model running the three ribbons never meet at one point — they cross each other at different heights, which is the textbook argument that the SM alone is not a complete Grand Unified Theory. Add supersymmetric partners (toggle "+ SUSY") and the extra particle content changes each bi, bending all three ribbons so they nearly converge around E ≈ 2×10¹⁶ GeV — the celebrated MSSM unification point, one of the main phenomenological arguments for low-energy supersymmetry.
- Energy scale — drag to any renormalization scale from the Z-boson mass up to the Planck scale; the moving triangle on the ribbons marks the current cross-section.
- Auto-scan — sweeps the scale slider continuously from M_Z to the Planck scale so you can watch the triangle open and close in real time.
- Spread (unif. quality) — the gap between the largest and smallest 1/αi at the current scale; it should shrink to a small value only near the SUSY unification point, and never gets small anywhere in the SM-only curve.
- A tiny triangle means the three forces are numerically indistinguishable at that energy — the physical picture behind "grand unification": one gauge group and one coupling constant above EGUT, splitting into three below it.
Real-world relevance: this near-perfect MSSM convergence (and the still-unobserved proton decay a full GUT predicts, since X/Y bosons at the unification scale mediate quark↔lepton transitions) is one of the strongest indirect hints — short of a direct high-energy discovery — that nature might unify the non-gravitational forces at all.