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.
Baryon acoustic oscillations (BAO) are subtle ripples in the distribution of matter left over from the early universe. These patterns act as a standard ruler, allowing astronomers to measure the expansion history of the cosmos and probe the nature of dark energy.
The observable universe spans 46.5 billion light-years in radius despite being 13.8 billion years old because space itself has expanded. This article explains the cosmic epochs, the role of inflation, and the evidence from the cosmic microwave background.
Dark matter provided the gravitational scaffolding for the first stars, gathering gas into halos where molecular hydrogen cooling could trigger collapse. Without dark matter, the first stars could not have formed so early in cosmic history, and their properties would be drastically different.
The Laser Interferometer Space Antenna (LISA) is poised to detect gravitational waves from the first generation of black holes—seeds of supermassive black holes formed in the early universe. This article explains how LISA will probe cosmic epochs from the Planck era to reionization, and why these observations will transform our understanding of structure formation.
