observable universe
Light's reachable extent
The observable universe is the portion of the universe from which light has had time to reach Earth since the Big Bang—roughly 93 billion light-years in diameter.
Beyond this boundary, light hasn't traveled long enough to be detected, so we cannot observe what lies there.
The limitation is about time and the speed of light, not about the universe having an edge.
- light-yearAstronomical distance measure
- redshiftWavelength stretch from recession
- megaparsecUnit measuring galactic distances
- cosmic scaleUniverse-sized frame of reference
- galaxy clusterGravitationally linked galaxy group
cosmology · astronomy · supercluster · infinity · cosmic inflation · Big Bang · Hubble · Hubble telescope · homogeneity · radiation · unfathomable · gravitational lensing · celestial · deep space · expansion · origins · boundaries · billions
- cosmosgalaxies, galaxy, stars, star, planets
- cosmologybig bang, Big Bang, big bang theory, dark matter, cosmic inflation
- cosmic structuresupercluster, galaxy cluster, filament, void, sheet
- naturalismnaturalism, literary realism, realism, determinism, empiricism
observe, universe, observer, universal, observant, observation, observed, observing, observance