Figure 46: Estimates of the baryon density [where ] over
time (updated [273] from [269]). BBN was already a well-established field prior to 1995; earlier
contributions are summarized by compilations (green ovals [480, 107]) that gave the long-lived
standard value [480]. More recent estimates from individual isotopes are shown as
triangles (2H), squares (4He), diamonds (3He), and stars (7Li). Estimates of the baryon density based
on analyses of the cosmic microwave background are shown by circles (dark blue for CDM; light
blue for no-CDM). No measurement of any isotope suggested a value greater than
prior to observation of the acoustic peaks in the microwave background (dotted lines), which might
be seen as a possible illustration of confirmation bias. Fitting the acoustic peaks in CDM requires
. More recent measurements of 2H and 4He have migrated towards the CDM
CMB value, while 7Li remains persistently problematic [111]. It has been suggested that turbulent
mixing might result in the depletion of primordial lithium necessary to reconcile lithium with the
CMB (upward pointing arrow [287]), while others [405] argue that this would merely reconcile some
discrepant stars with the bulk of the data defining the Spite plateau, which persists in giving a
7Li abundance discrepant from the CDM CMB value. In contrast, the amplitude of the second
peak of the microwave background is consistent with no-CDM and [269].
Consequently, from the perspective of MOND, the CMB, lithium, deuterium, and helium all give a
consistent baryon density given the uncertainties.
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