Figure 46

Figure 46: Estimates of the baryon density Ω h2 b [where h = H ∕(100 km s−1 Mpc −1) 0] 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 Ωbh2 = 0.0125 [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 ΛCDM; light blue for no-CDM). No measurement of any isotope suggested a value greater than 2 Ωbh = 0.02 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 ΛCDM requires Ω h2 > 0.02 b. More recent measurements of 2H and 4He have migrated towards the ΛCDM 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 ΛCDM CMB value. In contrast, the amplitude of the second peak of the microwave background is consistent with no-CDM and Ωbh2 = 0.014 ± 0.005 [269]. Consequently, from the perspective of MOND, the CMB, lithium, deuterium, and helium all give a consistent baryon density given the uncertainties.