Lambda-CDM model

Lore & Background

The model includes cosmic inflation to produce perturbations, which are characterized by additional parameters matched to observations. The light from astronomical observations passes through ionized space, where electrons can scatter it, altering anisotropies. The expansion of space is documented via redshift of spectral lines and time dilation in supernova light curves, attributed to a Doppler shift as light travels across expanding space. The expansion allows distant galaxies to recede faster than light, though local expansion is subluminal.

Reader's Guide

The ΛCDM model has been successful in modeling a broad collection of astronomical observations over decades, including the cosmic microwave background, large-scale structure, light-element abundances, and the accelerating expansion. It proposes cold dark matter as non-baryonic, cold, dissipationless, and collisionless, interacting only through gravity and possibly the weak force. Dark matter constitutes about 26.5% of the mass-energy density, while ordinary matter makes up 4.9%, with most ordinary matter unseen. The model's remaining issues challenge its assumptions and have led to many alternative models. The earliest epoch supported by observational evidence is cosmic inflation, followed by reheating and the hot Big Bang. Cosmic inflation addresses the horizon problem, and the universe may be larger than the observable particle horizon.

Did You Know?

• The ΛCDM model emerged in the late 1990s as a concordance cosmology after a period of inconsistent observations.
• Cold dark matter is hypothesized to be non-baryonic, cold, dissipationless, and collisionless.
• The model allows for distant galaxies to recede from each other at speeds greater than the speed of light.