Working definition
The cosmic microwave background is relic electromagnetic radiation observed across the sky with an almost blackbody spectrum and small anisotropies. ΛCDM is a parameterized cosmological model used to connect those measurements with expansion, matter content, initial fluctuations, and structure formation.
What is measured
- Multi-frequency maps measure microwave intensity and polarization.
- Calibration and beam models characterize instrument response.
- Foreground models separate Galactic and extragalactic emission.
What is inferred
- Angular power spectra summarize anisotropy statistics.
- Model likelihoods constrain cosmological parameters.
- Cross-checks combine CMB data with lensing, distance, and structure probes.
Fact-layer dependency
The explanatory layer cannot rewrite these fields.
time.utcInstantobserver.positionsubject.identifiersreference.framecoordinates.valuescoordinates.uncertaintyprovenance.providerWhat is observed
Multi-frequency maps measure microwave intensity and polarization. Calibration and beam models characterize instrument response. Foreground models separate Galactic and extragalactic emission.
The CMB is measured as nearly uniform relic microwave radiation with small temperature and polarization variations across the sky.
Boundary: A best-fit parameter is conditional on model and data choices.
How inference enters
Angular power spectra summarize anisotropy statistics. Model likelihoods constrain cosmological parameters. Cross-checks combine CMB data with lensing, distance, and structure probes.
Limits and unresolved questions
A best-fit parameter is conditional on model and data choices. Dark matter and dark energy labels do not identify their physical nature. Tensions between probes are not resolved by averaging them away.
The physical nature of dark matter and dark energy remains open even when ΛCDM fits many observations.
Boundary: Tensions between probes are not resolved by averaging them away.
Sources
Each source states both what it establishes and where its authority ends. Access dates record the last public verification.
- [1]Planck and the Cosmic Microwave Background · European Space Agency · accessed 2026-08-15
Establishes: The CMB as relic radiation, its near-blackbody spectrum, anisotropies, foregrounds, and use in constraining cosmological models.
Boundary: Cosmological parameters are conditional on a model, likelihood, foreground treatment, calibration, and combination of data sets.
- [2]What Is the Universe? · NASA Science · accessed 2026-08-15
Establishes: A broad synthesis of cosmic contents, scale, history, expansion, and the observationally inferred roles of dark matter and dark energy.
Boundary: Percentages and ages summarize model fits and observations; the physical nature of dark matter and dark energy remains unresolved.