CMB Maps

A CMB map is a snapshot of the oldest light in the universe, revealing tiny temperature variations that seeded all cosmic structure. This guide explains what the map shows, the major epochs from the Planck era to reionization, and how missions like COBE, WMAP, and Planck turned the cosmic microwave background into a precision tool for cosmology.

The cosmic microwave background is a fossil snapshot of the universe at 380,000 years old. This guide explains how to read its temperature and polarization maps, trace the major cosmic epochs from the Planck era to structure formation, and understand what the oldest light reveals about dark matter, dark energy, and the geometry of the cosmos.