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The horizon is the apparent curve that separates the surface of a celestial body from its sky when viewed from the perspective of an observer on or near the surface of the relevant body. This curve divides all viewing directions based on whether it intersects the relevant body's surface or not.
Horizon (archaeology) In archaeology, the general meaning of horizon is a distinctive type of sediment, artefact, style, or other cultural trait that is found across a large geographical area from a limited time period. [1] [2] [3] The term derives from similar ones in geology, horizon or marker horizon, but where these have natural causes ...
e. In astrophysics, an event horizon is a boundary beyond which events cannot affect an observer. Wolfgang Rindler coined the term in the 1950s. [1] In 1784, John Michell proposed that gravity can be strong enough in the vicinity of massive compact objects that even light cannot escape. [2] At that time, the Newtonian theory of gravitation and ...
Soil horizon. A cross section of a soil, revealing horizons. A soil horizon is a layer parallel to the soil surface whose physical, chemical and biological characteristics differ from the layers above and beneath. Horizons are defined in many cases by obvious physical features, mainly colour and texture.
Historical definition. The word horizontal is derived from the Latin horizon, which derives from the Greek ὁρῐ́ζων, meaning 'separating' or 'marking a boundary'. The word vertical is derived from the late Latin verticalis, which is from the same root as vertex, meaning 'highest point' or more literally the 'turning point' such as in a whirlpool.
Cosmological horizon. A cosmological horizon is a measure of the distance from which one could possibly retrieve information. [1] This observable constraint is due to various properties of general relativity, the expanding universe, and the physics of Big Bang cosmology. Cosmological horizons set the size and scale of the observable universe.
Horizon (geology) In geology, a horizon is either a bedding surface where there is marked change in the lithology within a sequence of sedimentary or volcanic rocks, or a distinctive layer or thin bed with a characteristic lithology or fossil content within a sequence. [1] Examples of the former can include things such as volcanic eruptions as ...
Particle horizon. The particle horizon (also called the cosmological horizon, the comoving horizon (in Scott Dodelson 's text), or the cosmic light horizon) is the maximum distance from which light from particles could have traveled to the observer in the age of the universe. Much like the concept of a terrestrial horizon, it represents the ...