Filaments, Voids & Superclusters: Physical Mechanisms

Dense nodes host galaxy clusters, filaments connect those nodes, walls or sheets contain extended galaxy concentrations, and voids occupy most cosmic volume with far fewer galaxies.

Tiny primordial density differences grow under gravity. Matter flows out of underdense regions and toward denser structures, producing anisotropic collapse into sheets and filaments before gathering into halos and clusters.

Three-dimensional redshift surveys reveal web-like galaxy distributions over enormous volumes. Weak lensing, peculiar velocities, and simulations show that dark matter traces a similar underlying network.

Gravity amplifies primordial density fluctuations anisotropically: collapse occurs first along one direction to form sheets, then along another to form filaments, and finally into dense halos and nodes. A more complete mechanism picture follows anisotropic collapse: matter first evacuates underdense regions, then flows toward sheets, along sheets into filaments, and finally into dense nodes. Peculiar velocities therefore contain dynamical information about how the web is still growing today.