analemmatic sundials how to build one and why they

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1、Analemmati Sundials:howtobuildoneandwhytheyworkCBuddandCSangwinDepartmentofathemati alS ien esUniversityofBath,Bath,BA27AY,U jbmaths.bath.a .uk, jsmaths.bath.a .ukune12,2000bbbbbbbbbbbAAbSbFbbbbbbThisarti leisavailableonlinefrom,http://pass.maths.org.uk/issue11/121
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2、atyouhavejustgotthelatestindigitalwat hes,withastopwat h,date,timesfromallovertheworld,andtheabilitytofun tionat4000fathoms.Thereisjustonesmallproblem:thebatterieshavegone at.However,ifthesunisshiningyoudon'tneedtouseawat hatall,be ausethesunmakesanex ellent lokwhi h(fortunately)doesn'tneedbatterie

3、sthat anrundown.Thisarti leisallaboutaparti ularkindofsundialandhowyou anbuildoneforyourself.
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CEeverlookdire tlyatthesun!Weoftentaketheproblemoftellingthetimeorofndingtheday'sdateforgrantedbutndingsolutionstobothofthesequestionsisvitaltoour ivilisation.Earlymenandwomenneededtoh

4、aveana uratenotionoftheseasonsinordertoknowwhentoplantandharvesttheir rops.As ivilisationdevelopeditbe ameimportanttoknowthetimeduringtheday.Twotimeswereobviousaseveryonewasawareofwhenthesunrose(dawn)andwhenitset(dusk).orea urateobservationsofthesunthenshowedthathavingrisen(intheEastintheorther

5、nhemisphere)it limbedtoitshighestpointinthesky,whi hisdueSouth(intheorthernhemisphere),beforedes endingtowardsitssettingpointintheWest.Thetimeofthehighestpointrea hedbythesun(whi hiswhentheshadowswereshortest)is alledoon.nowingdawn,oonandduskgaveusmorning,afternoonandnight.Every ivilisationhasb

6、eeninterestedinthewaythesunthemovesandastronomyandmathemati shavealwaysdevelopedalongsideea hother.Betterobservations alledforqui kerandmoreeÆ ientmathemati almethods.oredetailedtheorydrovepeopletomakemorea urateobservations.
nthiswayboththeoryandpra ti eevolvedtogether.
nthisarti lewegivesomethe

7、oryaboutthewaythesunmovesandthen on entrateonapra ti almethodofbuildingananalemmati sundial.Wehooseinitiallynottogivetoomu hjusti ationforthemathemati sbehindthe onstru tionofthisdial.Detailsofthetheoryoft