Big Bang nucleosynthesis (BBN) is the production of light elements during the first minutes of cosmic time. Its evidence comes from the remarkable agreement between predicted and observed primordial abundances, which also constrains the baryon density and supports the standard hot Big Bang model.
About three minutes after the Big Bang, the universe cooled to roughly a billion degrees, allowing protons and neutrons to fuse into light nuclei. This process, known as Big Bang nucleosynthesis, fixed the primordial hydrogen-to-helium ratio that still dominates the cosmos today.
In the late 1990s, two independent teams used Type Ia supernovae as standard candles to trace the universe’s expansion history. Their surprising conclusion—that cosmic expansion is accelerating—revolutionized cosmology and led to the concept of dark energy, a mysterious force driving the universe apart.
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.
Primordial helium, forged in the first minutes after the Big Bang, provides a crucial test of the hot Big Bang model. Its measured abundance matches theoretical predictions, reinforcing our understanding of the universe’s origin and evolution.
Explore the question of whether time began with the Big Bang, and journey through the major cosmic epochs—from the Planck epoch to the formation of stars and galaxies—guided by the standard Lambda-CDM model of cosmology.
In 1964, Arno Penzias and Robert Wilson accidentally discovered the cosmic microwave background (CMB) while testing a sensitive antenna at Bell Labs. Their measurement confirmed the Big Bang theory and revealed a relic of the universe’s infancy, forever changing cosmology.
Hot and cold spots in the cosmic microwave background are tiny temperature variations—about one part in 100,000—that reveal the seeds of galaxies and the physics of the early universe. This guide explains their origin, how missions like COBE, WMAP, and Planck measured them, and why they matter for cosmology.
The cosmic microwave background (CMB) is the oldest light in the universe, a relic of the hot Big Bang. This article explains how astronomers measure it from Earth, what it reveals about cosmic history, and why it anchors our modern understanding of the cosmos.
The Big Bang was not an explosion from a single point in space. It was the beginning of space and time itself, occurring everywhere in the universe simultaneously. This article explains the origin, key epochs, and evolution of the cosmos, from the Planck epoch to the present day, and why the universe has no center or edge.
