What&meisit?
Wherearewe?
LectureCredits:
OvertheEdgeoftheWorldbyLaurenceBergreen,HarperCollins.
Google“Vsauce”foreduca&onalandinteres&ngvideosonYouTube.
CollegeofFisheriesandOceanSciencesMarineScienceLectures:
“IntroductoryMarineScience”(111)and
“ConceptsinPhysicalOceanography”(419)and
“Introduc&ontoPhysicalOceanography”(620).
ClaudiusPtolemy(c.90-168)wasprobably
aGreekborninEgypt.Hewasa
mathema&cian,astronomerand
cartographerwhocreatedala&tude/
longitudesystemtodescribeloca&onsthat
servedforprac&calnaviga&onun&lthe
15thcentury.
JohannesKepler(1571-1630)wasaGerman
astronomerandmathema&cianwhotheorizedand
publishedin1609thattheplanets,includingEarth,
travelaroundthesuninellip&calorbits.Usinghis
theory,hewasabletocalculateprecisepredic&ve
tablesforplanetarymo&on.
SirIsaacNewton(1643-1727)wasanEnglish
mathema&cianwholaidthegroundworkfor
calculusanddidbreakthroughworkinop&cs
andgravita&on.HepublishedPrincipia
Mathema<cain1687whereheappliedthe
lawsofmo&ontothemo&onofceles&al
bodies,providingthemathema&cstoprove
Kepler’stheories.
Thesewouldbeusedbyfutureastronomersto
producenaviga&onaltables.Healsodeveloped
theuniversallawofgravita&on.
Newton’sSecondLaw:Force=MassxAccelera&on
or
Accelera&on=ForceperunitMass
but
Accelera&onisavelocitychangein&me.
Inoceanphysics,wetrytounderstandtheFORCESsowecanpredictVELOCITYormo&on.
InTordesillas,Spain,theSpanishandPortugueseagreedtoabidebyapapaldivisionwhichaddressedtheinterestsof
both.AgerthePortugueseprevailedontheSpanishrepresenta&vestomovetheline270leagueswest,itlay370
leagueswestoftheCapeVerdeIslands,atapproximately46°30'W,accordingtomoderncalcula&ons.Thenew
boundarygavethePortugueseampleaccesstotheAfricancon&nentbywaterandallowedthePortuguesetoclaimthe
newlydiscoveredlandofBrazil.However,nego&a&onsdraggedonforyears.WhenPopeAlexanderVIdiedin1503,he
wassucceededbyPopeJuliusII,whoin1506agreedtothechanges,andtheTreatyofTordesillasachieveditsfinal
form.However,itwastheresultofmanycompromises,andthetreatycreatedmoreproblemsthanitsolved.Foremost
wasthattheinabilitytofixtheline’sloca&onbecausecosmologistsdidnotyetknowhowtodeterminelongitude—nor
wouldtheyforanothertwohundredyears!
In1519FerdinandMagellan,withsupportfromSpain,departedSevillewith
afleetoffivevesselsandabout260sailorstovoyagearoundtheworldand
securelandsforSpain.Thevoyagelasted3yearsandwaswellchronicled
byAntonioPigafena.
IntheAgeofDiscovery,the15thCentury,morethanhalftheworldwas
unexplored,unmapped,andmisunderstoodbyEuropeans.Marinersfeared
theycouldsailovertheedgeofworld,believedseamonsterslurkedinthe
oceandepthswai&ngtodevourthem,andwhentheycrossedtheequator,
theoceanwouldboilthemtodeath.Pigafena’saccountwasunusualasit
wasbasedondirectobserva&ons,withoutaddingdreamedupaccountsof
monstersorwhirlpools.
MagellanwaskilledinthePhilippinesin1521,butoneship,with18
survivors,returnedtoSevillein1522undertheSpanishCaptainJuan
Sebas&anElcano,comple&ngthefirstknowncircumnaviga&on.
AntonioPigafenawasaVene&anscholar,aboutthirtyyearsoldatthe&me
ofMagellan’sexpedi&on.Hewasamanoflearning(he“readmanybooks”),
hadreligiousconvic&on,anda“cravingforexperienceandglory.”
Pigafenakeptarecordofthevoyagethatwasnotadry,factualpilot’slog,
butratheramorepersonal,anecdotal,andfree-flowingaccount.His
loyal&esbelongedtoMagellanalone,nottoanyoftheotherofficers.For
Pigafena,theArmadadeMoluccawasthetangibleresultofMagellan’s
daring.
FromthemomentthefleetlegSeville,Pigafenakeptadiaryofeventsthat
graduallyevolvedfromarou&neaccountoflifeatseatoashockingly
graphicandcandiddiarythatservesasthebestrecordofthevoyage.
FranciscoAlbo,Trinidad’s
pilot,alsokeptalogbook,
andsomeofthesurviving
sailorsgaveextensive
interviewsanddeposi&ons
ontheirreturntoSpain,or
wrotetheirownaccounts
frommemory.
TheSpanishcityofSevillehadlimita&ons
asaportbecauseoftheshallownessof
theGuadalquivirRiver.
Shipshadtobesmallandlightto
nego&atetotheAtlan&c.Magellan’s
flagship,Trinidad,therefore,weighed
100tons;SanAntonio,whichcarried
manyoftheprovisions,weighed120
tons;Concepción90tons,Victoria85
tons;andSan5ago,tobeusedfor
reconnaissance,weighedjust75tons.
MagellantookonatSevilletwomainitems,wineandhardtack.Winewastaxfreeandwasstoredincasksandinpipes
sealedwithacorkandpitch.Meat,bacon,ham,andsaltedbeefweretakenalong,aswellassevencowsandthreepigs,
generallyslaughteredjustbeforeorjustagerdeparture.Barrelsofcheese,almondsintheshell,mustard,andcasksof
figswerealsoloadedonboard.Thefleetalsocarrieddriedandsaltedfish—sardines,cod,anchovies,andtuna.
Hardtackconsistedofcoarsewheatflour,includingthehusk,kneadedwithhotwater(nevercold),andcookedtwice.
Theresult,atough,brinlebiscuitknownasbiscocho,wasstoredforuptoamonthbeforeitwassold.Inevitably,the
hardtackdegradedinthehumidcondi&onsatsea,andwhenitbecamesog,andronen,andinedible,itwascalled
mazamorra;thesailorsboiledthestuffun&litturnedintoamushknownascalandra,saidtobesovilethateven
starvingsailorsrefusedit.Theshipsalsoheldstoresofflourinwoodenbarrelsthatwaskneadedwithseawaterand
grilledasakindoftor&lla.
Nooneansweredtothedescrip&onofcookbecausethejobwasconsidereddemeaning.Thecrewtookturnscooking,or
paidappren&cestocookforthem.Duringfoulweathertherewasnocookingatall,andthesailorsenduredcoldrepasts
ofhardtack,saltedmeat,andwine.
Magellansecuredatroveofnaviga&onalmaterial
thatconsistedofthirty-fivecompasses,awooden
astrolabe,sixofthemorecommonmetalastrolabes,
twenty-onewoodenquadrants,andeighteen
hourglasses,someofwhichMagellanpurchased
himself.Thereweretwenty-fourcharts;mostwere
topsecret.Anyunauthorizedindividualcaughtwith
achartcouldbepunishedseverely,evenwithdeath,
sochartswerekeptunderlockandkey,andogen
underarmedguard.
Ofthetotalnumberofcharts,sixhadbeendraged
byprincipalcosmographerRuyFaleiro.Eighteen
othersweretheworkofthecosmographerNuño
Garcia,sevenoftheseunderthedirec&onofFaleiro,
andelevenmoreunderthedirec&onofMagellan.
Thefleetalsocarriedquan&&esofpreparedblank
parchment,aswellasdriedskinstomakes&llmore
parchment,ifnecessary,foraddi&onalchart-making.
In1519FerdinandMagellanroundedSouthAmericathroughwhatisnowknownastheStraitofMagellan,andthen
sailedacrossthePacifictothePhilippines.AnchoringatthePhilippineislandofCebu,Magellanmetwiththelocal
chiefwhosoughthisassistanceinconqueringarivaltribeonnearbyMactan.Intheensuingfight,Magellan,hitbya
poisonedarrow,died.
hnps://annoyzview.files.wordpress.com/2015/04/banle-of-machtan-21.jpg
InthePhilippines,MagellantriedtoclaimthelandfortheSpanishcrown.
AlthoughthearrivalofMagellanwaswelcomedbymostofisland’srulers,a
localchiefnamedLapu-LapusawMagellanasanenemyofthestate.Lapu-Laoy
mayhavecometoPhilippinesfromBorneoduringtheprosperousreignof
RajahHumabon.Inanothersource,Lapu-Lapuisdepictedasthedescendentof
DatuMangal,thechiefofMactanIslands.HeisnowaherointhePhilippines,
honoredwithstatuesforleadingtheApril27,1521banlewhereMagellanwas
killed.
hnps://annoyzview.wordpress.com/2015/04/15/lapu-lapu-the-warrior-hero-of-phillipines/
San&ago
Island,
Cape
Verde
WhenAlboandPigafenanearedthecomple&onoftheircircumnaviga&on,theywereastonishedtonotethattheir
calcula&onsdifferedbyonedayfromthelocaldate.Theirvoyagearoundtheworldactuallytookonedaylonger
thantheirrecordsshowed:
“OnWednesday,theninthofJuly[1522],wearrivedatonetheseislandsnamedSan&ago,whereweimmediately
senttheboatashoretoobtainprovisions.[...]Andwechargedourmenintheboatthat,whentheywereashore,
theyshouldaskwhatdayitwas.TheywereansweredthattothePortugueseitwasThursday,atwhichtheywere
muchamazed,fortousitwasWednesday,andweknewnothowwehadfallenintoerror.ForeverydayI,being
alwaysinhealth,hadwrinendowneachdaywithoutanyintermission.But,asweweretoldsince,therehadbeen
nomistake,forwehadalwaysmadeourvoyagewestwardandhadreturnedtothesameplaceofdepartureasthe
sun,whereforethelongvoyagehadbroughtthegainoftwenty-fourhours,asisclearlyseen.”
DatesduringMagellan’svoyageweregivenintheJuliancalendarthatwasineffectfromthe&meofJuliusCaesar.It
hadbeenadopted,withminormodifica&ons,bytheChris&anchurchesaroundtheworld,includingthoseofSpain
whohadsponsoredMagellan’svoyage.In1582,sixtyyearsagerMagellan’svoyage,Spain,France,andother
EuropeancountriesmigratedtotheGregoriancalendar,decreedbyPopeGregoryXIIIanddesignedtocorrect
incrementalerrorsintheJuliansystem.Ittookmorethantwocenturiestocompletethetransi&ontothenew
calendarthroughoutEurope,sinceProtestantna&onsresistedthechange.Tocorrectforaccumulatederrors,tendays
wereomined,sothatOctober5,1582,intheJuliancalendarsuddenlybecameOctober15,1582,intheGregorian.
WhataretheJulianandGregorianCalendars?
Whydoweneedthem?
Onesideraldayistherota&onoftheEarthonerevolu&onaboutitsaxis.
Thisaddedrota&onmakesita“SOLARDAY”
Theearthrotatesaboutthesuninanellipse.Sothespeedalongtheellipsepathisnotconstant.Thus,the“green”
lineinthepreviousslidechangesdependingonwheretheearthisalongthatellipse.
Thatmeansthe“solarday”isvariable.Thelengthof“aday”isnotconstantoverthecourseofyear.
Sun
Sketchisnottoscale
A
Thisangleissmallerthanthisangle.
Sotheearthhastoturnalinle“less”atA
thanoveratBtoalignwiththesun.
ThesolardayisshorteratAandlongeratB!
B
Thisamountof&mevaries!
Nowitisshorter!
Let’susean“average”dayof24hours!