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- Tropical_year abstract "A tropical year (also known as a solar year), for general purposes, is the 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 synchronized 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 (the sidereal year).Since antiquity, astronomers have progressively refined the definition of the tropical year. The Astronomical Almanac Online Glossary 2015 states:year, tropical: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". (Borkowski 1991, p. 122)The mean tropical year on January 1, 2000, was about 365.2421897 ephemeris days according to the calculation of Laskar (1986); each ephemeris day lasting 86,400 SI seconds. By 2010 this had decreased to 365.2421891 (365 ephemeris days, 5 hours, 48 minutes and 45.14 seconds). This is about 365.242181 mean solar days, though the length of a mean solar day is constantly changing.".
- Tropical_year wikiPageExternalLink 1986A%26A...157...59L.
- Tropical_year wikiPageExternalLink 1992JBAA..102...40M.
- Tropical_year wikiPageExternalLink 2004JHA....35..327M.
- Tropical_year wikiPageExternalLink nph-iarticle_query?1991JRASC..85..121B&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf.
- Tropical_year wikiPageExternalLink Glossary.html.
- Tropical_year wikiPageExternalLink index.html.
- Tropical_year wikiPageExternalLink sp4218.htm.
- Tropical_year wikiPageExternalLink ser7.dat.
- Tropical_year wikiPageExternalLink general.html.
- Tropical_year wikiPageExternalLink 131123ExplanatorySupplementAstronomicalAlmanac.
- Tropical_year wikiPageID "25453345".
- Tropical_year wikiPageLength "28809".
- Tropical_year wikiPageOutDegree "118".
- Tropical_year wikiPageRevisionID "678599239".
- Tropical_year wikiPageWikiLink Albert_Einstein.
- Tropical_year wikiPageWikiLink Alfonsine_Tables.
- Tropical_year wikiPageWikiLink Alfonsine_tables.
- Tropical_year wikiPageWikiLink Apollo_11.
- Tropical_year wikiPageWikiLink Aries_(astrology).
- Tropical_year wikiPageWikiLink Astronomical_Almanac.
- Tropical_year wikiPageWikiLink Astronomical_year_numbering.
- Tropical_year wikiPageWikiLink Astronomy_in_medieval_Islam.
- Tropical_year wikiPageWikiLink Astronomy_in_the_medieval_Islamic_world.
- Tropical_year wikiPageWikiLink Atomic_clock.
- Tropical_year wikiPageWikiLink Axial_precession.
- Tropical_year wikiPageWikiLink Axial_precession_(astronomy).
- Tropical_year wikiPageWikiLink Bighorn_sheep.
- Tropical_year wikiPageWikiLink Bureau_International_des_Poids_et_Mesures.
- Tropical_year wikiPageWikiLink Calendar_reform.
- Tropical_year wikiPageWikiLink Category:Calendars.
- Tropical_year wikiPageWikiLink Category:Technical_factors_of_astrology.
- Tropical_year wikiPageWikiLink Category:Time_in_astronomy.
- Tropical_year wikiPageWikiLink Category:Units_of_time.
- Tropical_year wikiPageWikiLink Category:Western_astrology.
- Tropical_year wikiPageWikiLink Celestial_equator.
- Tropical_year wikiPageWikiLink Celestial_mechanics.
- Tropical_year wikiPageWikiLink Centre_national_de_la_recherche_scientifique.
- Tropical_year wikiPageWikiLink Charles-Eugène_Delaunay.
- Tropical_year wikiPageWikiLink Computus.
- Tropical_year wikiPageWikiLink Coordinated_Universal_Time.
- Tropical_year wikiPageWikiLink Copernican_heliocentrism.
- Tropical_year wikiPageWikiLink Copernicus.
- Tropical_year wikiPageWikiLink December_solstice.
- Tropical_year wikiPageWikiLink Degree_(angle).
- Tropical_year wikiPageWikiLink Dennis_McCarthy_(scientist).
- Tropical_year wikiPageWikiLink Earth.
- Tropical_year wikiPageWikiLink Ecliptic.
- Tropical_year wikiPageWikiLink Edmond_Halley.
- Tropical_year wikiPageWikiLink Edmund_Halley.
- Tropical_year wikiPageWikiLink Edward_M._Reingold.
- Tropical_year wikiPageWikiLink Edward_Reingold.
- Tropical_year wikiPageWikiLink Einstein.
- Tropical_year wikiPageWikiLink Ephemeris_day.
- Tropical_year wikiPageWikiLink Ephemeris_time.
- Tropical_year wikiPageWikiLink Equinox.
- Tropical_year wikiPageWikiLink First_Council_of_Nicaea.
- Tropical_year wikiPageWikiLink French_National_Centre_for_Scientific_Research.
- Tropical_year wikiPageWikiLink Galaxies.
- Tropical_year wikiPageWikiLink Galaxy.
- Tropical_year wikiPageWikiLink General_Conference_on_Weights_and_Measures.
- Tropical_year wikiPageWikiLink General_Theory_of_Relativity.
- Tropical_year wikiPageWikiLink General_relativity.
- Tropical_year wikiPageWikiLink George_Coyne.
- Tropical_year wikiPageWikiLink Global_Positioning_System.
- Tropical_year wikiPageWikiLink Greek_language.
- Tropical_year wikiPageWikiLink Greenwich_meridian.
- Tropical_year wikiPageWikiLink Gregorian_calendar.
- Tropical_year wikiPageWikiLink Hipparchus.
- Tropical_year wikiPageWikiLink IBM_SSEC.
- Tropical_year wikiPageWikiLink IBM_Selective_Sequence_Electronic_Calculator.
- Tropical_year wikiPageWikiLink International_Atomic_Time.
- Tropical_year wikiPageWikiLink International_Bureau_of_Weights_and_Measures.
- Tropical_year wikiPageWikiLink International_Celestial_Reference_Frame.
- Tropical_year wikiPageWikiLink International_Earth_Rotation_Service.
- Tropical_year wikiPageWikiLink International_Earth_Rotation_and_Reference_Systems_Service.
- Tropical_year wikiPageWikiLink International_System_of_Units.
- Tropical_year wikiPageWikiLink Isaac_Newton.
- Tropical_year wikiPageWikiLink Jean_Meeus.
- Tropical_year wikiPageWikiLink Jet_Propulsion_Laboratory.
- Tropical_year wikiPageWikiLink Johannes_Kepler.
- Tropical_year wikiPageWikiLink Joseph-Louis_Lagrange.
- Tropical_year wikiPageWikiLink Joseph_Louis_Lagrange.
- Tropical_year wikiPageWikiLink Julian_calendar.
- Tropical_year wikiPageWikiLink June_solstice.
- Tropical_year wikiPageWikiLink LAGEOS.
- Tropical_year wikiPageWikiLink Latitude.
- Tropical_year wikiPageWikiLink Libra_(astrology).
- Tropical_year wikiPageWikiLink Longitude.
- Tropical_year wikiPageWikiLink Louis_Essen.
- Tropical_year wikiPageWikiLink Lunar_Laser_Ranging_experiment.
- Tropical_year wikiPageWikiLink Lunar_laser_ranging.
- Tropical_year wikiPageWikiLink March_equinox.
- Tropical_year wikiPageWikiLink Mars.
- Tropical_year wikiPageWikiLink Mean_solar_day.
- Tropical_year wikiPageWikiLink Mercury_(planet).
- Tropical_year wikiPageWikiLink Moon.
- Tropical_year wikiPageWikiLink Nicolaus_Copernicus.
- Tropical_year wikiPageWikiLink Northern_solstice.
- Tropical_year wikiPageWikiLink Northward_equinox.