Part VI: The Dark Sector

Dark Matter & Dark Energy

Approximately 95% of the universe's energy content is invisible: ~27% dark matter and ~68% dark energy. Dark matter, inferred from galaxy rotation curves, gravitational lensing, and CMB anisotropies, provides the gravitational scaffolding for structure formation. Dark energy, discovered through Type Ia supernova observations in 1998, drives the accelerating expansion of the universe. Together they define the ΛCDM concordance model of cosmology.

Ωₗ ≈ 0.68

Dark Energy Fraction

Ωₜₘ ≈ 0.27

Dark Matter Fraction

w ≈ −1

Dark Energy EoS

Topics in This Part

1. Dark Matter

Observational evidence, rotation curves, gravitational lensing, WIMP and axion candidates, direct and indirect detection

2. Dark Energy

Type Ia supernovae discovery, cosmological constant, ΛCDM model, equation of state, and quintessence alternatives

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