Period of time for the ecliptic longitude of the Sun to increase 360°
A tropical year or solar year (or tropical period) is the time that the Sun takes to return to the same position in the sky – as viewed from the Earth or another celestial body of the Solar System – thus completing a full cycle of astronomical seasons. For example, it is the time from vernal equinox to the next vernal equinox, or from summer solstice to the next summer solstice. It is the type of year used by tropical solar calendars.
The tropical year is one type of astronomical year and particular orbital period. Another type is the sidereal year (or sidereal orbital period), which is the time it takes Earth to complete one full orbit around the Sun as measured with respect to the fixed stars, resulting in a duration of 20 minutes longer than the tropical year, because of the precession of the equinoxes.
Since antiquity, astronomers have progressively refined the definition of the tropical year. The entry for "year, tropical" in the Astronomical Almanac Online Glossary states:[1]
the period of time for the ecliptic longitude of the Sun to increase 360 degrees. Since the Sun's ecliptic longitude is measured with respect to the equinox, the tropical year comprises a complete cycle of seasons, and its length is approximated in the long term by the civil (Gregorian) calendar. The mean tropical year is approximately 365 days, 5 hours, 48 minutes, 45 seconds.
An equivalent, more descriptive, definition is "The natural basis for computing passing tropical years is the mean longitude of the Sun reckoned from the precessionally moving equinox (the dynamical equinox or equinox of date). Whenever the longitude reaches a multiple of 360 degrees the mean Sun crosses the vernal equinox and a new tropical year begins".[2]
The mean tropical year in 2000 was 365.24219 ephemeris days, each ephemeris day lasting 86,400 SI seconds.[3] This is 365.24217 mean solar days.[4] For this reason, the calendar year is an approximation of the solar year: the Gregorian calendar (with its rules for catch-up leap days) is designed so as to resynchronise the calendar year with the solar year at regular intervals.
^Cite error: The named reference AAOG2020 was invoked but never defined (see the help page).
^Borkowski 1991, p. 122.
^Cite error: The named reference SIsecond was invoked but never defined (see the help page).
^Cite error: The named reference Richards2013_587 was invoked but never defined (see the help page).
A tropicalyear or solar year (or tropical period) is the time that the Sun takes to return to the same position in the sky – as viewed from the Earth...
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calendar year incorrectly summarised Earth's tropicalyear as 365.25 days, the Gregorian calendar makes these exceptions to follow a calendar year of 365...
Southernmost. This means that the tropical zone includes everywhere on Earth which is a subsolar point at least once during the solar year. Thus the maximum latitudes...
Calendar reform Common year Fiscal year ISO 8601 ISO week date Leap year Model yearTropicalyear Seasonal year "calendar year". Merriam-Webster. Retrieved...
the precession of the equinoxes. The sidereal year is 20 min 24.5 s longer than the mean tropicalyear at J2000.0 (365.242 190 402 ephemeris days). At...
correctly this system could have allowed the Roman year to stay roughly aligned to a tropicalyear. However, since the pontifices were often politicians...
whole numbers facilitates the construction of a lunisolar calendar. A tropicalyear (about 365.24 days) is longer than 12 lunar months (about 354.36 days)...
make the average calendar year 365.2425 days long, more closely approximating the 365.2422-day 'tropical' or 'solar' year that is determined by the Earth's...
1955, the tropicalyear, considered more fundamental than the sidereal year, was chosen by the IAU as the unit of time. The tropicalyear in the definition...
duration of a tropicalyear is 365.24219 days, while the long-term average duration of a lunar year is 354.36707 days, the average lunar year is (365.24219...
assumes that a tropicalyear is exactly 127⁄19 times that, i.e., about 365.2468 days. Thus it overestimates the length of the tropicalyear (365.2422 days)...
a tropical solar calendar [citation needed]. The duration of the mean calendar year of such a calendar approximates some form of the tropicalyear, usually...
the period in each year when most tropical cyclogenesis occurs in the Atlantic. However, the formation of subtropical or tropical cyclones is possible...
tropical climates within the tropical climate group: tropical rainforest climate (Af), tropical monsoon climate (Am) and tropical savanna or tropical...
Gregorian times and dates vary slightly from year to year as the Gregorian calendar shifts relative to the tropicalyear. These variations remain within less...
in tropical years can be computed by dividing the difference between the sidereal year and tropicalyear by the length of the tropicalyear. Tropical year...
calendar. A tropicalyear is approximately 365.2422 days long and a synodic month is approximately 29.5306 days long, so a tropicalyear is approximately...
with the tropicalyear, which does not contain an exact number of days. The common year of 365 days has 52 weeks and one day, hence a common year always...
accurate than Ptolemy's, and their calculation of the length of the tropical solar year was more accurate than that of the Spanish when the latter first...
storms are referred to as "tropical cyclones". In modern times, on average around 80 to 90 named tropical cyclones form each year around the world, over half...
In 2024, tropical cyclones will form in seven major bodies of water, commonly known as tropical cyclone basins. Tropical cyclones will be named by various...
of arc per year, or 1 degree every 71.6 years. At present, the rate of precession corresponds to a period of 25,772 years, so tropicalyear is shorter...
An area of tropical monsoon climate (occasionally known as a sub-equatorial, tropical wet climate or a tropical monsoon and trade-wind littoral climate)...
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