The Early Universe
In the first few hundred thousand years, the universe was a seething plasma of energy and elementary particles — too hot for atoms to form, too dense for light to travel. Here is how order emerged from chaos.
Why Inflation Changed Everything
Without inflation, the universe would be lumpy and inconsistent. Inflation smoothed out all irregularities in a single violent expansion. But crucially, quantum fluctuations during inflation were stretched to cosmic scales — becoming the seeds of galaxies, clusters, and the large-scale structure we observe today.
Inflation also explains why the universe appears flat (not curved), and why opposite ends of the visible universe have nearly identical temperatures despite never being in causal contact. These are the three pillars of inflationary cosmology: flatness, horizon, and monopole problems — all solved.
Key Stages
The universe expanded exponentially — faster than the speed of light — driven by a hypothetical field called the inflaton. A region smaller than a proton expanded to the size of a marble, then continued expanding. This explains why the CMB is so uniform across the sky.
As the universe cooled below 10¹² K, free quarks and gluons condensed into hadrons — primarily protons and neutrons. For every billion antimatter particles, there were a billion-and-one matter particles. This tiny imbalance is why matter exists today.
The universe cooled enough for protons and neutrons to fuse. About 75% hydrogen and 25% helium-4 were produced, along with trace deuterium and lithium. This ratio precisely matches observations in the oldest stars.
After the CMB was released, the universe was filled with neutral hydrogen — transparent but dark. No stars existed yet. Gravity slowly gathered hydrogen into dense filaments, setting the stage for the first stars.
Electrons combined with protons to form neutral hydrogen. The universe became transparent, releasing the Cosmic Microwave Background — the oldest light in existence, still detectable today at 2.725 K.
The Antimatter Mystery
When matter and antimatter meet, they annihilate each other. The Big Bang should have created equal amounts — which would have destroyed everything, leaving a universe of pure energy. Yet matter won. For every billion antimatter particles, there was one extra matter particle. This tiny asymmetry, called CP violation, is one of the deepest unsolved mysteries in physics. Without it, you would not exist.