The cosmic web is the large-scale structure of the universe, where matter is not distributed uniformly but instead organized into a network of filaments, sheets, and voids. In this structure, galaxies and galaxy clusters are located along dense filaments, while vast cosmic voids lie between them.
The intergalactic medium (IGM) primarily resides in these filaments, composed of diffuse gas—mostly hydrogen and helium—tracing the gravitational scaffolding shaped by dark matter. Gas flows along these filaments into galaxies and clusters, fueling star formation and galaxy growth.
Observational evidence for the cosmic web comes from:
- Galaxy surveys, which reveal the filamentary distribution of galaxies.
- Quasar absorption lines, which map the IGM along different sightlines.
- Numerical simulations, which reproduce the web-like structure resulting from gravitational collapse and cosmic expansion.
The cosmic web provides a framework for understanding how matter assembles in the universe, linking small-scale processes like star formation to the largest structures shaped by dark matter and cosmic expansion. It is the skeleton of the universe, connecting galaxies across billions of light-years.