early-universe

JWST's confirmed discoveries from 2022 to 2026: ancient galaxies too massive for theory, exoplanet biosignature debates, star formation in infrared, and solar system science.

The cosmic microwave background (CMB) is thermal radiation from the universe's first 380,000 years, now cooled to about 2.7255 K. Its tiny ripples seeded every galaxy.

Cosmic inflation is a proposed burst of exponential expansion in the first fraction of a second after the Big Bang, stretching space by a factor of at least about 10²⁶. It explains why the universe is flat and uniform and where galaxies came from. Its best-known direct test, a 2014 claim by BICEP2, turned out to be dust.

After the Big Bang's fireball faded, the universe entered a dark age lasting hundreds of millions of years — no stars, no galaxies, just a sea of neutral hydrogen. Then the first stars ignited, and their ultraviolet radiation gradually reionized the cosmos in one of the most dramatic phase transitions in cosmic history.

Quasars outshine entire galaxies from a region smaller than the solar system. They powered the early universe, shaped galaxy formation, and are now our most powerful probes of cosmic history. Here's what they actually are.