The Lambda-CDM Model
Definition
The standard model of cosmology: a flat, expanding Universe dominated by a cosmological constant (Λ) and cold dark matter (CDM).
Scientific overview
ΛCDM is the simplest model that fits nearly all cosmological observations — the cosmic microwave background, large-scale structure, the light-element abundances, and the accelerating expansion — with just six parameters. It describes a Universe that is about 68% dark energy, 27% dark matter, and 5% ordinary matter.
Historical development
Emerged in the late 1990s as dark-energy evidence combined with CMB and structure data; refined to percent-level precision by WMAP and Planck.
Evidence
- Fits the full CMB power spectrum (Planck)
- Reproduces large-scale structure and BAO
- Matches Big Bang nucleosynthesis and the accelerating expansion
Parameters
| Dark energy (Λ) | ≈ 68% | Planck Collaboration |
| Cold dark matter | ≈ 27% | Planck Collaboration |
| Ordinary matter | ≈ 5% | Planck Collaboration |
| Geometry | Flat (Ω ≈ 1) | Planck Collaboration |
Key ingredients
Open questions
- What are dark matter and dark energy?
- Is the Hubble tension a sign of new physics?
- Is dark energy truly a constant?
Rests on
Related topics
Knowledge connections
- IncludesThe Big Bang
- IncludesCosmic Inflation
- IncludesBig Bang Nucleosynthesis
- IncludesRecombination
- IncludesThe Cosmic Dark Ages
- IncludesCosmic Dawn & the First Stars
- IncludesReionization
- IncludesStructure Formation
- IncludesThe Present Universe
- IncludesThe Hubble Tension
- IncludesThe Age of the Universe
- IncludesThe Cosmic Microwave Background
- IncludesBaryon Acoustic Oscillations
- IncludesDark Matter
- IncludesDark Energy
- IncludesThe Cosmological Constant (Λ)
- Depends onCosmic Inflation
- Related toDark Matter
- Related toDark Energy
- Related toThe Cosmological Constant (Λ)
- Related toThe Big Bang
- Related toThe Cosmic Microwave Background
Sources & references
The primary and reference sources this topic draws on.
- Planck CollaborationESA Planck mission / Planck Collaboration
Cosmic microwave background maps and the cosmological parameters of the ΛCDM model.
- NASANational Aeronautics and Space Administration
Mission data, planetary science, space telescopes, and public-domain imagery.
Most NASA-produced imagery is in the public domain; individual items are checked for usage terms before publication.