Cosmic web

The cosmic web is the universe’s large-scale network of galaxies and dark matter, arranged in filaments, clusters, and vast voids.

Gravitational instability: The growth of small density fluctuations under gravity, which can produce increasingly concentrated structure. It drives the growth of matter concentrations that become the web’s filaments and clusters.
Cosmic filament: An elongated, dense structure of galaxies and dark matter connecting richer regions of the cosmic web. Filaments form the web’s threadlike backbone.
Galaxy redshift survey: An astronomical survey that measures galaxy positions and redshifts to map three-dimensional large-scale structure. Redshift surveys reveal the web’s galaxy distribution across cosmic distances.
Galaxy formation: The process by which gas, stars, and dark matter assemble into galaxies. Galaxies form within halos supplied by matter flowing along the web.
Cold dark matter: A model in which dark matter moves slowly enough for small-scale structure to form early. Its gravitational scaffolding helps determine how the web develops.
Galaxy cluster: A gravitationally bound system containing hundreds to thousands of galaxies, hot gas, and dark matter. Clusters occupy dense nodes where several filaments meet.
Weak gravitational lensing: The subtle distortion of background images by foreground matter’s gravitational field. It maps dark matter in filaments even where galaxies provide few visible tracers.
Cosmic flows: The large-scale motions of galaxies and matter under the influence of gravity and cosmic expansion. Flows carry matter from voids toward filaments and clusters.
Cosmic microwave background: The relic radiation released when the early universe became transparent, carrying evidence of primordial density fluctuations. Its measured fluctuations provide initial conditions for structure formation.
Cosmic void: A vast region with substantially fewer galaxies than the cosmic average. Voids define the large empty spaces between the web’s denser structures.

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