Lithium-7 Plateau Discrepancy (Spite)

The Spite plateau refers to the nearly constant lithium-7 abundance measured in the atmospheres of old metal-poor halo stars: regardless of their temperature or metallicity, these stars show Li/H ~ 1.6 × 10⁻¹⁰, a value that is a factor of two to three below the primordial ⁷Li abundance predicted by standard Big Bang nucleosynthesis (BBN) using the baryon density inferred from CMB observations. This discrepancy has persisted for four decades and resists resolution within ΛCDM: the BBN prediction is robust, the stellar observations are precise, and no stellar depletion mechanism consistently reduces lithium by the required factor across all halo stars of different temperatures and ages without also destroying other elemental signatures that are not observed to be depleted.

Successive Collision Theory resolves the lithium discrepancy through the pre-existing stellar populations inherited from the two colliding spacetime pockets. The debris field that became our observable universe contained thermalized gas from prior stellar generations, some of which had already processed significant amounts of ⁷Li through p-p chain burning, spallation reactions on cosmic rays, and incorporation into stellar interiors. This pre-processed gas mixed with the freshly synthesized BBN products during the thermalization epoch and early post-collision evolution, diluting the lithium abundance in the material from which the first observed halo stars formed. The degree of dilution is set by the ratio of pre-existing processed material to fresh BBN products in the collision debris, and SCT predicts this ratio is such that the effective lithium available to first-generation star formation is reduced by the observed factor of two to three relative to the pure BBN prediction.

Additionally, the SCT collision thermalization did not instantaneously and uniformly mix all pre-existing and freshly synthesized material. Spatial inhomogeneities in the debris field — set by the angular momentum distribution of the initial collision — produced regions with different mixing ratios of pre-processed and BBN-fresh gas. This predicts a small but nonzero scatter in the Spite plateau: halo stars formed in regions with higher fractions of pre-processed gas should show slightly lower ⁷Li, while those in less-processed regions should approach the BBN prediction more closely. Precision spectroscopy of large halo star samples has indeed revealed a low level of scatter in the plateau consistent with this picture, distinguishing the SCT dilution explanation from both pure stellar depletion models and pristine BBN scenarios.