Equation 8 · Part 1 · From Origins to Frontier: A History of Precision Cosmology
Symbol H_0
What this part means
a model-dependent inference from an early-universe ruler, not a direct local measurement.
Its job in the formula
is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.
Full expression→Symbol H_0→Article meaning
Where the article explains it
This is the crux of the tension discussed below: Planck’s is a model-dependent inference from an early-universe ruler, not a direct local measurement.
The passage around this formula
…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 ruler, not a direct local…
Learn the underlying idea
A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.
Open the illustrated subscripts: which member of a family? guide →
See this notation across published equations →
Sources cited in the article section
- [5] Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Parameter Results ↗
- [6] Planck 2018 results. VI. Cosmological parameters ↗
These citations provide research context; check each source for the exact claim it supports.