= Solution
\Image[../../../paper-312-cmb-temperature-power.svg]
{title=Schematic cosmic microwave background temperature power spectrum and source contributions}
{description=The Sachs-Wolfe contribution controls the low-multipole plateau, acoustic physics produces the peaks, the Doppler contribution is phase shifted, and photon diffusion suppresses the spectrum in the high-multipole damping tail.}
The conventional vertical variable is $D_\ell=\ell(\ell+1)C_\ell/(2\pi)$ in $\mu{\rm K}^2$, plotted against the dimensionless angular multipole $\ell$. The <Sachs-Wolfe effect> supplies a nearly flat large-angle plateau for $\ell\lesssim30$. The total spectrum has its first acoustic peak near $\ell\simeq220$ with $D_\ell$ of order $5\times10^3\,\mu{\rm K}^2$, followed by further <Cosmic microwave background acoustic peaks>; the <Doppler CMB anisotropy> is phase shifted relative to the photon-density oscillation. At $\ell\gtrsim1000$, <Cosmic microwave background diffusion damping> lets photons random-walk across perturbations during recombination and produces the rapidly falling damping tail.
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