Cosmic inflation is a theory that proposes the universe underwent an extremely rapid expansion in its earliest moments, just a tiny fraction of a second after the Big Bang. During this brief period, the universe grew exponentially—expanding much faster than the speed of light (without violating relativity, since space itself was expanding).
This idea helps explain several puzzling features of the universe:
- Uniformity (Horizon Problem): Distant regions of the universe have nearly identical temperatures and properties, even though they are so far apart that light couldn’t have traveled between them since the Big Bang—unless they were once close together before inflation spread them apart.
- Flatness Problem: Inflation drove the curvature of space toward flatness, which aligns with current observations of the universe being geometrically flat on large scales.
- Lack of Relics (Monopole Problem): Inflation would have diluted exotic relics predicted by earlier theories, such as magnetic monopoles, making them extremely rare or nonexistent in the observable universe.
Cosmic inflation also provided the seeds for the large-scale structure of the universe. Tiny quantum fluctuations during inflation were stretched to cosmic scales, later forming galaxies and clusters.
Although still a theoretical framework, inflation is widely supported due to its ability to resolve key cosmological issues and is consistent with precise measurements of the cosmic microwave background.