particle horizon; cosmic horizon
In cosmology, the boundary of the observable universe beyond which light has not had time to reach us since the Big Bang. Related to 事象の地平線 (event horizon), but distinct.
See also: 事象の地平線
Beyond the cosmic horizon, we cannot observe with current technology.
The particle horizon is determined by the age of the universe and the speed of light.
Event horizon of a black hole, a gravitational boundary from which nothing can escape. 宇宙の地平線 is a cosmological horizon based on light travel time, not gravity.
Compound of 宇宙 (universe) + の (possessive particle) + 地平線 (horizon). A direct translation of the English term 'cosmic horizon' or 'particle horizon'.