The Hubble tension is a growing discrepancy between two precise measurements of the universe’s expansion rate. This article explains the conflict, its implications for cosmology, and places it within the full story of cosmic evolution from the Planck epoch to today.
The scalar spectral index (n_s) quantifies how primordial density fluctuations vary with scale. A value of 1 indicates perfect scale invariance, while observations from Planck and earlier missions show n_s ≈ 0.96, a key confirmation of inflationary cosmology and a crucial input to the ΛCDM model.
CMB acoustic peaks are the fingerprints of sound waves in the early universe, imprinted on the cosmic microwave background. They reveal the universe’s geometry, composition, and evolution, confirming the Lambda-CDM model.
The Cosmic Dawn marks the pivotal era when the first stars and galaxies ignited, ending the cosmic Dark Ages and transforming the universe from darkness into the structured cosmos we observe today. This guide traces the universe’s evolution from the Planck epoch through Reionization, explaining how the first luminous objects formed and how telescopes like JWST are revealing this hidden chapter of cosmic history.
Comoving distance is a fundamental measure in cosmology that factors out the expansion of the universe, providing a stable ruler for cosmic scales. This guide explains how comoving distance relates to redshift, traces the major epochs of cosmic evolution, and shows how modern missions have mapped our universe’s history.
The Atacama Cosmology Telescope (ACT) is a decommissioned six-meter millimeter-wave telescope in Chile that mapped the cosmic microwave background with high precision, helping to refine the standard model of cosmology and reveal the universe’s composition and evolution.
The recombination epoch, about 380,000 years after the Big Bang, marks the moment when electrons and protons combined to form neutral hydrogen, allowing light to travel freely and giving rise to the cosmic microwave background. This article explores this pivotal era and the full cosmic timeline.
The cosmic microwave background (CMB) is the oldest light in the universe, a relic of the hot, dense state that existed just 380,000 years after the Big Bang. Its discovery and precise measurement provided decisive evidence for the Big Bang model, ruling out steady-state alternatives and opening a new era of precision cosmology.
The CMB dipole anisotropy is a small temperature variation in the cosmic microwave background caused by our motion relative to the universe’s rest frame. It reveals the Solar System’s velocity of 370 km/s and serves as a fundamental calibration for all CMB measurements.
The Integrated Sachs-Wolfe (ISW) effect is a subtle imprint on the cosmic microwave background caused by the changing gravitational potentials of large-scale structure as photons travel through an accelerating universe. It provides a unique observational window into dark energy and the evolution of cosmic structure.
