What is the length of daylight at the equator - Social Science - Motions of the Earth

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What is the length of daylight at the equator

Chirag Mohitkar · Answer

Day length, orlength of day, orlength of daytime, is the time each day from the moment the upper limb of thesun's disk appears above thehorizonduringsunriseto the moment when the upper limb disappears below thehorizonduringsunset Because of thediffusionandrefractionofsunlightby theatmosphere, there is actuallydaylighteven when thesunis slightly below thehorizon The period when it is still somewhat light even though the sun is below thehorizonis calledtwilight Contents[hide] 1Description 2Alternate definition 3Increasing day length 4See also 5References 6External links Description[edit] In general, the length of a day varies throughout the year, and depends uponlatitude This variation is caused by the tilt of the Earth's axis of rotation with respect to theecliptic planeof the Earth around the sun At thesolsticeoccurring about June 2022, the north pole is tilted toward the sun, and therefore thenorthern hemispherehas days ranging in duration from just over 12 hours in the southern portion of theTropic of Cancerto 24 hours in theArctic Circle, while thesouthern hemispherehas days ranging in duration from just under 12 hours in the northern portion of theTropic of Capricornto zero in theAntarctic Circle At theequinoxoccurring about September 2223, the poles are neither tilted toward nor away from the sun, and the duration of a day is generally about 12 hours all over the Earth At thesolsticeoccurring about December 2022, the south pole is tilted toward the sun, and therefore thesouthern hemispherehas days ranging in duration from just over 12 hours in the northern portion of theTropic of Capricornto 24 hours in theAntarctic Circle, whereas thenorthern hemispherehas days ranging in duration from just under 12 hours in the southern portion of theTropic of Cancerto zero in theArctic Circle At theequinoxoccurring about March 1921, the poles are again aligned so that the duration of a day is generally about 12 hours all over the Earth In each hemisphere, the higher thelatitude, the shorter the day duringwinter Betweenwinterandsummer solstice, the day's duration increases, and the rate of increase is larger the higher the latitude A fast increase of day length is what allows a very short day onwinter solsticeat 60 degrees latitude (either north or south) to reach about 12 hours by thespring equinox, while a slower increase is required for a much longer day onwinter solsticeat 20 degrees latitude (again, either north or south) to reach 12 hours by thespring equinox The rate of change of day duration is generally fastest at theequinoxes, although at high latitudes the change is similar for several weeks before and after the equinoxes The rate of change of day duration at eachsolsticeis zero as the change goes from positive to negative, or vice versa Some interesting facts are as follows: On theEquator, the duration of daylight is not exactly 12 hours all the year round, but rather — because of atmosphericrefractionand the size of the Sun — exceeds 12 hours by about 7 minutes each day; Because the sun is north of the equator for almost 4 days more than half the year, because of the eccentricity of Earth's orbit, the duration of the average day at a givenlatitudein thenorthern hemisphereexceeds the duration of the average day at the samelatitudein thesouthern hemisphereby a few minutes; During a few days around theequinoxes—about March 1922 and September 2124—both poles experience simultaneously 24 hours of daytime, mainly because of atmospheric refraction Each pole has only onesunriseand onesunsetper year, around the time of theequinoxes Each polessunriseis nearly coincident with the other'ssunset, with minor differences mainly resulting from atmospheric refraction Alternate definition[edit]

Day length, sunset and sunrise in Madrid (40º25') during 2011 Sorry, your browser either has JavaScript disabled or does not have any supported player You can download the clip or download a player to play the clip in your browser " style="position: relative; display: inline-block; width: 250px; height: 125px;"

Sunshine at 12:00 UTC during a year More conveniently, atmospheric refraction is ignored and the center of the sun is often used in place of the upper limb for computing a day's duration Whensunriseandsunsetdo occur, the day duration can be computed as 2o/15, where ois thesunsethour anglein degrees () given by thesunset equation Whensunriseandsunsetdo not occur during the course of a day, the day duration is either 0 or 24 hours Increasing day length[edit] The earth is constantly losing angular velocity and rotational energy through a process calledtidal acceleration, which leads to a slow lengthening of the day A century ago, the average day was about 1 7millisecondsshorter than today,[1]while in the lateNeoproterozoicabout 620 million years ago a day had only about 21 9±0 4 hours [2] See also[edit] Fluctuations in the length of day Photoperiodism(for effects on living organisms) Postglacial rebound Solar day Sun declination Sunrise equationNepali Method References[edit] Jump up^McCarthy, D D Seidelmann, P K TIME: From Earth Rotation to Atomic Physics Weinheim: Wiley-VCH (2009) pp 8889 Jump up^Williams, George E (2000) "Geological constraints on the Precambrian history of Earth's rotation and the Moon's orbit" Reviews of Geophysics38(1): 3760 Bibcode:2000RvGeo 38 37W doi:10 1029/1999RG900016 External links[edit]

Wikimedia Commons has media related toDay length Compute precise times of rising and setting of the Sun, Moon and planets Sun, Moon and Earth Applet, by Jurgen Giesen Formulae to calculate day length, by Herbert Glarner Calculate sun rise/set, by U S Naval Observatory Datasets on earth rotation and alignment, IERS, International Earth Rotation and Reference Systems Service (formerly: International Earth Rotation Service) Sun chart generator with Daylight Sunrise Sunset table values Sunrise, sunset, daylight in a graph