CFA2 Great Wall

The CFA2 Great Wall, identified in the Center for Astrophysics redshift survey, was among the first recognized examples of wall-like galaxy clustering on scales well above what ΛCDM's correlation functions robustly predict. Its coherence length and the sharpness of its boundaries in redshift space both exceed standard model expectations for structures assembled from gravitational amplification of inflationary perturbations. Successive Collision Theory identifies the CFA2 Great Wall as a fossil compression shell — a segment of the swept collision front boundary that has been enriched in galaxies because the density enhancement at the shell wall promoted early star formation, galaxy formation, and subsequent merger-driven growth. The sharpness of the wall's boundaries in redshift space reflects the physical sharpness of the original compression front: matter swept ahead of the collision front was deposited in a layer whose thickness was dynamically set by the collision physics rather than by the gentle cosmological collapse that ΛCDM invokes.

The exact clustering statistics of the CFA2 Great Wall — its overdensity contrast, its velocity dispersion across the wall, and the galaxy morphology distribution within it — all carry the imprint of the original collision energy deposition. The overdensity contrast is higher on the side facing the collision impact direction, where the sweeping was most energetic; the opposite face is more diffuse because the collision front had partially exhausted its momentum. This asymmetry in wall overdensity across the wall's plane is a distinctive SCT prediction that cannot be reproduced by ΛCDM's symmetric gravitational collapse from a density peak, and it provides a testable discriminant between the two frameworks using galaxy number counts and velocity dispersion profiles on either face of the structure.