The sphere is the whole sky, painted with a synthetic temperature map: a base of 2.725 K (the CMB's average blackbody temperature) plus a sum of spherical-harmonic-like ripples whose count is set by the angular scale slider and whose size is set by the anisotropy amplitude, on top of a dipole term caused by our own motion through the CMB rest frame. Color runs from blue (colder) through the panel's temperature scale to red (hotter), the same convention real CMB maps from COBE, WMAP and Planck use.
T(θ,φ) = T₀ + A·Σ sin(ℓ·θ)cos(ℓ·φ) + D·cos(θ)
B(ν,T) ∝ ν³ / (e^(hν/kT) − 1) [Planck blackbody law]
- Anisotropy amplitude — how strong the ripple pattern is; the real sky's fluctuations are only ~18 µK against a 2.725 K background, exaggerated here for visibility.
- Angular scale — how many ripples fit around the sky; low ℓ is large smooth patches, high ℓ is fine structure, mirroring the multipole expansion cosmologists actually fit to CMB data.
- Dipole strength — the largest real CMB anisotropy, caused by the Solar System's own motion (~370 km/s) relative to the CMB rest frame, which Doppler-shifts one hemisphere warmer and the other cooler.
- The bottom-right panel plots the Planck blackbody spectrum for the mean temperature, with a marker at the 160 GHz peak frequency — the spectral shape that confirmed the CMB is genuine thermal radiation from the early universe, not scattered starlight.
Real-world relevance: missions like COBE, WMAP and Planck measured exactly this kind of anisotropy map to pin down the universe's age, composition and geometry — the tiny ripples visualized here are the seeds that gravity later grew into galaxies and galaxy clusters.