Tropical Year
type: Unit
description: A tropical year (also known as a solar year), for general purposes, is the length of time that the Sun takes to return to the same position in the cycle of seasons, as seen from Earth; for example, the time from vernal equinox to vernal equinox, or from summer solstice to summer solstice. Because of the precession of the equinoxes, the seasonal cycle does not remain exactly synchronised with the position of the Earth in its orbit around the Sun. As a consequence, the tropical year is about 20 minutes shorter than the time it takes Earth to complete one full orbit around the Sun as measured with respect to the fixed stars. Since antiquity, astronomers have progressively refined the definition of the tropical year, and currently define it as the time required for the mean Sun's tropical longitude (longitudinal position along the ecliptic relative to its position at the vernal equinox) to increase by 360 degrees (that is, to complete one full seasonal circuit).
applicable system: CGS
applicable system: CGS-EMU
applicable system: CGS-GAUSS
applicable system: IMPERIAL
applicable system: SI
applicable system: USCS
conversion multiplier: 31556925.216
conversion multiplier SN: 3.1556925216E7
has dimension vector: A0E0L0I0M0H0T1D0
has quantity kind: Time
iec61360 code: 0112/2///62720#UAB029
informative reference: https://cdd.iec.ch/cdd/iec62720/iec62720.nsf/Units/0112-2---62720%23UAB029
scaling of: SEC
symbol: a{tropical}
ucum code: a_t
unece common code: D42
unit for quantity kind: Time
wikidata match: Q189607
alternative label: solar year