Astronomy Hypertext_ Time Keeping Systems

Astronomy Hypertext_ Time Keeping Systems - 1/15/12...

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Unformatted text preview: 1/15/12 Astronomy Hypertext: Time Keeping Systems As tronom H perte t Time Keeping S stems Lat est Modif icat ion: Jul 22, 2002 R .A ' .T E ' .A ' .S S , " " . Side re al Time O si dereal da ' .T . T l ocal si dereal t i me (LST) (LHAVE), E ' .L 15 E ' .T ,1 0 0 , 000 15 1, 24 , . Solar Time A sol ar t i me . O apparent sol ar da ' S .T :F , S' E' ( S' , .A . S , (LHAS) + 12 , S K ). S mean sun. I , 1 , . Mean sol ar t i me (LHAS) + 12 , , , .S , .T physics.gmu.edu/~jevans/astr103/ , , T S ' /earthSky_timeKeepingSystems.html , 1/3 1/15/12 Astronomy Hypertext: Time Keeping Systems a ie d i g he ea , i +15 . A t ropi cal ear, a ea f ea , i e a 365.2422 ea a e he S c ee e e ia d he ec i ic i h si dereal ear, he he ha d, i he e i d f he S ' e i i e i ae he e i d f Ea h' bi a e i . Beca e he S , a ea a da i ge ha a ide ea da b 3 56 a da . I e e e e ec he e a e i i h e ec he f Ea h' a a i f a i e. he i e i i . The a ,a d a d S andard Time Ob i f he a ea a i e i e , i i diffe e a ace e a a ed b diffe e ce i gi de. T ge a d hi i c e ie ce, he a da d i e e a i d ced i 1884. The e a e 24 i e e , each he e ica 15 ide, i h he e i e e ce e ed G ee ich, E g a d, he 0 e idia f gi de, a d ceedi g ea e f G ee ich. Th gh he a i a e ce e f each e he a da d e idia , h e ca ea a i e i he a da d i e i hi he e. I he U i ed S a e a d Ca ada, he a da d e idia aea f : St andard Ti mes for t he Uni t ed St at es and Canada S andard M e ridian Time Zone 60 A a ic a da d i e (AST) 75 Ea e a da d i e (EST) 90 Ce a a da d i e (CST) M 105 ai a da d i e (MST) 120 Pacific a da d i e (PST) 135 Y 150 a da d i e (YST) A a a- Ha aii a da d i e (AHST) The e a da d i e e a e e ec i e 4h , 5h , 6h , 7h , 8h , 9h , a d 10h behi d G ee ich ea i e (GMT), a a uni versal t i me (UT). Ti e cha ge b 1h a he a e e c ea e b da . The e fe e ha e i eg a b da ie i ca c di i . A he e aec ie ha ac a a e e a a da d i e e , i hich he e i e c ee he ae e i e. The cce i e i e e ei he e ea f G ee ich i he d a 180 gi de a he i nt ernat i onal dat e l i ne, hich a e h h 12 e. The ha f i f he e e f he i e i 1d ahead f he e e h gh he a da d i e i he a e i each ha f. A a e e c ig Sa F a ci c , f e a e, gai a da , he ea e a e i g i he da . physics.gmu.edu/~jevans/astr103/ /earthSky_timeKeepingSystems.html ee ha f a a d he gh he ce e f he he ha f ea f he i e he da e i e f T i e di ec i ea 2/3 1/15/12 Astronomy Hypertext: Time Keeping Systems Cale nda The c ca e da f a cie e e a ba ed he a c c e f 29.5d , beca e cha ge i he M ' ha e a e eadi a a e . Si ce 12 a h ca be c ai ed i a ica ea a h e be f i e , a e a h a added f i e i e b i g he ea bac ched e. A e ch i e he a h i h he ea e e ed a i fac . The Eg ia e e he fi ba e hei ca e da a ica ea f 365.25d . Thei ea c i ed f 12 h f 30d each, i h 5d e a e a ide a he e d f he ea f ce eb a i . H e e , b he i e he J l i an cal endar a ad ed Ja a 1, 45 B.C., i had be ade 445d g i de b i g he ea bac ched e. The J ia ca e da c i ed f 365d i h e e f h ea bei g 366d . The e e g h f he ica ea i 365d 5h 48 46 , ab 11 14 h e ha 365.25d . He ce, he ge ea ed i he J ia ca e da e i a di c e a c f 3d i 400 . B 1582 A.D., he acc a ed diffe e ce a ed 10d , he da e f he e a e i had e ea ed f Ma ch 21, a he i e f he C ci f Nicaea c e ed i 325 A.D., Ma ch 11. Acc di g , P e G eg XIII ca ed he a e Ca i e i e he J ia ca e da . df Hi i a d 10 he ca e da , ha he da f i g Th da , Oc be 4, 1582, he eb beca e F ida , Oc be 15, 1582. A d a id f e ca e da di c e a cie , ce ea di i ib e b 400 e e ea ea , ch a 1600 a d 2000. Thi e ca e da beca e a he Gregori an cal endar, a d i a eadi ad ed b Ca h ic c ie . The L he a a d P e a fi a ade he ad i i 1700. Whe G ea B i ai a d he A e ica c ie cha ged he G eg ia ca e da i 1752, Se e be 2 had be f ed b Se e be 14, he di c e a c ha i g g 12d . Ea i hi ce he c ie i E e a d A ia fi a ad ed he G eg ia ca e da e e c e i . The e e G eg ia d i 3300 . H e e , i acc ac i i ca e da i acc a e ab 1 ed be d ha b i e e i g a e a ec d be ee da e e fe ea c e aef a be f i eg a i ie i he ce e ia c c . 1995, J. C. Ev ans Physics & Ast ronomy Depart ment , George Mason Univ ersit y Maint ained by J. C. Ev ans; j ev ans@gmu.edu physics.gmu.edu/~jevans/astr103/ /earthSky_timeKeepingSystems.html 3/3 ...
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