Cosmological concept · Cosmology
The Cosmic Horizon
Cosmology & UniverseEstablished Science
Definition
The boundary beyond which light has not had time to reach us — the edge of the observable Universe.
Scientific overview
The particle horizon marks the farthest distance from which signals could have reached us. Because the expansion is accelerating, there is also an event horizon: galaxies beyond a certain distance are receding so fast that light they emit now will never reach us.
Related topics
Knowledge connections
- Related toThe Observable Universe
- Related toThe Observable Universe
- Related toDark Energy
Sources & references
The primary and reference sources this topic draws on.
- NASANational Aeronautics and Space Administration
Mission data, planetary science, space telescopes, and public-domain imagery.
Most NASA-produced imagery is in the public domain; individual items are checked for usage terms before publication.