Inflation was a brief but colossal expansion that smoothed the universe and solved the horizon problem. It stretched quantum fluctuations to cosmic scales, seeding galaxies. Without inflation, the universe would look wildly irregular. It also flattened the universe’s curvature. This theory predicts patterns observed in the CMB. Inflation links quantum physics to cosmology and explains why the cosmos is so uniform.
It matters because inflation provides a mechanism for the universe’s large-scale uniformity.
It also underpins modern cosmological models and structure formation theories.
The universe expanded faster than light in its first trillionth of a trillionth of a second.
CERN [cern.ch]