Learn how cosmic microwave background maps are made—from raw time-ordered data to full-sky images—and explore the cosmic epochs they reveal, from the Planck epoch to structure formation.
Explore the cosmic dark ages—the period when the universe was shrouded in neutral hydrogen—and the full timeline from the Planck epoch to the formation of galaxies. Learn how the first stars reionized the cosmos and how missions like JWST are unveiling this hidden era.
CMB-S4 was a planned next-generation ground-based observatory designed to map the cosmic microwave background with over 500,000 superconducting detectors. Although cancelled in July 2025, its science goals — testing inflation, measuring neutrino masses, and probing new light relics — remain central to modern cosmology.
Reionization is the epoch when the first stars and galaxies ionized the neutral hydrogen that filled the early universe, transforming it from opaque to transparent. This article explores the physics, timeline, and evidence for this cosmic milestone, from the Big Bang to the present day.
The cosmic distance ladder is the succession of methods by which astronomers determine distances to celestial objects, from nearby stars to the edge of the observable universe. Each rung relies on the previous step for calibration, enabling measurements of cosmic expansion and the evolution of the cosmos.
The cosmic dark ages were a period when the universe was filled with neutral hydrogen gas that blocked all light. This era began after recombination and ended when the first stars and galaxies reionized the gas, allowing photons to travel freely. It is a critical chapter in cosmic history, bridging the afterglow of the Big Bang and the birth of structure.
The cosmic microwave background (CMB) is the oldest light in the universe, but it is contaminated by emissions from our galaxy and distant sources. This article explains the techniques astronomers use to separate the CMB signal from these foregrounds, and how these efforts reveal the universe’s earliest moments and subsequent evolution.
Dive into the geometry and topology of the cosmos—from local curvature to global shape—and trace the universe’s evolution from the Planck epoch to the present, with insights from the cosmic microwave background and missions like COBE, WMAP, and Planck.
Dark energy makes up about 70% of the universe and drives the accelerating expansion of space. Whether it is constant or changing will determine if the cosmos ends in a Big Freeze, Big Rip, or Big Crunch. Recent surveys hint that dark energy may be weakening, but the standard Lambda-CDM model remains the consensus.
CMB foregrounds are astrophysical emissions from our galaxy and extragalactic sources that contaminate cosmic microwave background observations. They are especially problematic for polarization measurements, where synchrotron and thermal dust radiation can be polarized at 10–40%, overwhelming the faint primordial B-mode signal that would confirm cosmic inflation.
