the first fraction of a secondReputable sourceWell documented
Cosmic Inflation
On the timeline · around the first fraction of a second · The First Instants
What happened
A tiny fraction of a second after the Big Bang, the universe underwent 'inflation' — expanding faster than the speed of light, ballooning from smaller than an atom to larger than the visible universe almost instantly.
Why it matters
Inflation explains why the universe looks so smooth and geometrically flat, and its tiny quantum ripples became the seeds from which all galaxies later grew.
How we know
Inflation is inferred from patterns in the cosmic microwave background. Scientists still don't know what triggered it.
Sources
- NASA. Hubble and the Big Bang · Reputable source