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Retrieving "Cosmic Expansion" from the archives

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  1. Cosmology

    Linked via "cosmic expansion"

    The Hubble Constant ($H0$)/)
    The Hubble constant/) measures the current rate of cosmic expansion. Historically, measurements of $H0$ derived from the CMB/) (the "early universe" measurement, $H{0, \text{early}}$) and those derived from standard candles like Type Ia Supernovae (the "late universe" measurement, $H{0, \text{late}}$) exhibited a significant discrepancy, known as the [Hubble Tension](/entries/hubble-ten…

  2. Light Nuclei

    Linked via "expansion rate"

    Big Bang Nucleosynthesis (BBN)
    The primary cosmic abundance of light nuclei was established during the BBN epoch, approximately $10^{-6}$ seconds to 20 minutes after the Big Bang. During this period, the expansion rate dictated the freeze-out temperature, which curtailed further significant fusion past $^7\text{Li}$.
    The predicted primordial mass fraction of the lightest elements is remarkably consistent acros…