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where is the physical size of the sound horizon at recombination — how far a pressure wave in the primordial plasma could travel before the plasma became neutral and transparent — and is the angular diameter distance to that same epoch. Planck measures directly from the angular spacing of peaks in the CMB power spectrum to extraordinary precision; converting that angle into a present-day expansion rate requires assuming a cosmological model (matter content, radiation content, and the equation of state of dark energy) to relate and to . This is the crux of the tension discussed below: Planck’s is a model-dependent inference from an early-universe…
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Equation 3 · Astronomy & Cosmology
From Origins to Frontier: A History of Precision Cosmology
This mathematical expression combines the displayed quantities; its precise role follows from the surrounding article text.
where is the physical size of the sound horizon at recombination — how far a pressure wave in the primordial plasma could travel before the plasma became neutral and transparent — and is the angular diameter distance to that same epoch. Planck measures directly from the angular spacing of peaks in the CMB power spectrum to extraordinary precision; converting that angle into a present-day expansion rate requires assuming a cosmological model (matter content, radiation content, and the equation of state of dark energy) to relate and to . This is the crux of the tension discussed below: Planck’s is a model-dependent inference from an early-universe…
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Equation guide → · Article →Equation 7 · Astronomy & Cosmology
From Origins to Frontier: A History of Precision Cosmology
This mathematical expression combines the displayed quantities; its precise role follows from the surrounding article text.
where is the physical size of the sound horizon at recombination — how far a pressure wave in the primordial plasma could travel before the plasma became neutral and transparent — and is the angular diameter distance to that same epoch. Planck measures directly from the angular spacing of peaks in the CMB power spectrum to extraordinary precision; converting that angle into a present-day expansion rate requires assuming a cosmological model (matter content, radiation content, and the equation of state of dark energy) to relate and to . This is the crux of the tension discussed below: Planck’s is a model-dependent inference from an early-universe…