The cosmic microwave background (CMB) power spectrum is a cornerstone of modern cosmology. It maps the tiny temperature fluctuations in the universe’s oldest light, revealing the composition, geometry, and evolution of the cosmos from the Planck epoch to the present day.
The cosmic microwave background (CMB) power spectrum is a detailed map of temperature fluctuations in the oldest light of the universe, revealing the seeds of all cosmic structure. This guide explains how it is measured, what it tells us about the universe’s origin and evolution, and the key cosmic epochs it illuminates.
The two-point correlation function quantifies how galaxies and matter are clustered, encoding the universe’s history from quantum fluctuations to the cosmic web. This guide explains its definition, measurement, and role in tracing cosmic epochs from the Planck era to today.
Dark matter halos provided the gravitational scaffolding for the first black holes. Their mass, spin, and merger history determined whether primordial gas collapsed directly into massive seeds or formed smaller stellar remnants that later grew.
The Lyman-alpha forest is a series of absorption lines in quasar spectra caused by neutral hydrogen in the intergalactic medium. It serves as a powerful probe of cosmic structure, revealing the distribution of gas from the epoch of reionization to the present day, and providing a window into the evolution of the universe.
The flatness problem is a cosmological fine-tuning issue: the universe appears almost perfectly flat, requiring extreme fine-tuning in the early universe. Inflation explains this by driving spatial curvature to zero.
The universe is made almost entirely of matter, yet the Big Bang should have produced equal amounts of matter and antimatter. This article explores the baryon asymmetry problem, the cosmic epochs from the Planck era to structure formation, and the ongoing search for answers.
Electron-positron annihilation was a pivotal event in the first second after the Big Bang, transferring entropy to photons and neutrinos, setting the stage for nucleosynthesis and the cosmic microwave background. This article explores its role in the cosmic timeline, from the lepton epoch to recombination.
Deuterium, a heavy isotope of hydrogen, was forged in the first minutes after the Big Bang. Its measured primordial abundance matches theoretical predictions with remarkable precision, providing powerful confirmation of the hot Big Bang model and constraining the baryon density of the universe.
The integrated Sachs–Wolfe (ISW) effect is a secondary anisotropy in the cosmic microwave background caused by the time variation of gravitational potentials along the line of sight. It arises when the universe’s expansion accelerates—most notably due to dark energy—and provides a unique probe of dark energy and the growth of cosmic structure.
