TIME AND OCEAN STUDY

The Weekend Australian - Review - - Visual Arts -

Be­lief in a flat Earth has to­day be­come ironic short­hand for any wil­fully ob­scu­ran­tist po­si­tion. None­the­less, through­out the past two cen­turies, amid the tri­umph of sci­ence and tech­nol­ogy, there have been ob­sti­nate at­tempts by some bi­b­li­cal fun­da­men­tal­ists to ar­gue for a lit­eral in­ter­pre­ta­tion of scrip­ture and deny the spheric­ity of our planet.

It might come as a sur­prise to such peo­ple to re­alise that at the zenith of Chris­tian civil­i­sa­tion, in the high Mid­dle Ages, no ed­u­cated per­son doubted that the Earth was spher­i­cal. Dante’s whole vi­sion of the cos­mos in The Di­vine Com­edy, com­posed in the very early 14th cen­tury, is pred­i­cated on the idea of the Earth as a globe around which the sun, moon and the other five known plan­ets, and ul­ti­mately the fixed stars, ro­tate in cir­cu­lar or­bits.

In­deed the en­tire sys­tem of as­tron­omy and astrol­ogy, which was de­vel­oped in the Hel­lenis­tic pe­riod and fas­ci­nated the Mid­dle Ages, as­sumed spheric­ity and cir­cu­lar or­bits, each of the 12 signs of the zo­diac rep­re­sent­ing 30 de­grees of a full cir­cle. This model un­der­pins the con­cep­tion, en­trenched for cen­turies in med­i­cal and psy­cho­log­i­cal the­ory, that in­di­vid­u­als are im­printed with cer­tain char­ac­ter­is­tics by the po­si­tion of the cos­mos at the mo­ment of their birth.

The only mat­ter that pro­voked op­po­si­tion from the church was the re­place­ment of the geo­cen­tric model with the he­lio­cen­tric one, al­though even this the­sis, which opened the way to a dis­turbingly de­cen­tred uni­verse, was not con­tro­ver­sial when first pro­posed by Coper­ni­cus, and only the in­flu­ence of Span­ish arch-con­ser­va­tives forced the rel­a­tively lib­eral pope Ur­ban VIII to si­lence his friend Galileo in 1633.

The re­al­i­sa­tion that the Earth was a sphere seems to go back to Aris­to­tle, and its di­men­sions were cal­cu­lated in the fol­low­ing cen­tury by the Alexan­drian as­tronomer and ge­og­ra­pher Eratos­thenes. Know­ing that the sun was di­rectly above Aswan at noon on the sum­mer sol­stice, and mea­sur­ing the shadow of an obelisk in Alexan­dria at the same time, he found that the sun there was slightly more than 7 de­grees from be­ing di­rectly over­head: this meant the Earth’s cir­cum­fer­ence was about 50 times the dis­tance from Aswan to Alexan­dria.

A spher­i­cal Earth in­ci­den­tally raised the ques­tion of the north­ern and south­ern hemi­spheres and with it the idea that the lat­ter must hold a sig­nif­i­cant con­ti­nen­tal mass to bal­ance the African and Eurasian con­ti­nents al­ready known to the an­cients. Hence one of the most in­trigu­ing as­pects of the proto-his­tory of Aus­tralia: that the ex­is­tence of the south­ern land was pos­tu­lated in the­ory long be­fore Euro­peans set foot on it, in con­trast to Amer­ica, whose ex­is­tence came as a com­plete sur­prise.

The an­cient ge­og­ra­phers knew of the frozen North Pole and cor­rectly pos­tu­lated a cor­re­spond­ingly cold South Pole, and they also knew that tem­per­a­tures rose as one ap­proached the equa­tor. For some time there was a be­lief that just as the poles were too cold for hu­man life, the equa­tor was too hot, and thus we might never be able to cross the so-called tor­rid zone and de­ter­mine whether there was in­tel­li­gent life in the south­ern hemi­sphere.

It was prob­a­bly this as much as any­thing else that dis­turbed bi­b­li­cal fun­da­men­tal­ists, since it would throw into chaos ev­ery­thing from the story of hu­man­ity’s de­scent from Adam and Eve to the idea that Christ came to re­deem our sins. It was hard enough, as it was, to ex­plain why Christ had not re­vealed his mes­sage to the vast ma­jor­ity of al­ready known hu­man­ity.

Eratos­thenes also de­vised the sys­tem of ge­o­graph­i­cal co-or­di­nates that we still use, the grid of lat­i­tude and lon­gi­tude that al­lows us to plot any po­si­tion on the globe. But there was a fun­da­men­tal dif­fer­ence be­tween the two axes of this sys­tem, for while the equa­tor is a nat­u­ral zero de­gree for lat­i­tude, there is no such nat­u­ral ref­er­ence line for lon­gi­tude. It was en­tirely by con­ven­tion — and re­flect­ing Bri­tish mar­itime dom­i­nance at the time — that the zero merid­ian was fi­nally set at the Royal Ob­ser­va­tory at Green­wich.

But even af­ter a zero merid­ian had been es­tab­lished, lon­gi­tude pre­sented a still more in­tractable dif­fi­culty. It was rel­a­tively easy to work out by ob­ser­va­tion of the sun and stars how far north or south you had sailed, but it was very dif­fi­cult to know how far around the globe you were. We can see the re­sult of this in early maps that often seem to show the north- A replica of John Har­ri­son’s first marine time­keeper, H1, on show at the Na­tional Mar­itime Mu­seum; Har­ri­son’s marine time­keeper H4 (1759), right; Lar­cum Ken­dall’s marine time­keeper K2 (1771) bot­tom right south di­men­sions of coun­tries more ac­cu­rately than the east-west ones.

The most fa­mous con­se­quence of this prob­lem was the un­der­es­ti­ma­tion of the west­ward dis­tance be­tween Europe and Asia that lay be­hind the re­mark­able voy­age of Christo­pher Colum­bus in 1492. It was a bold ad­ven­ture by any stan­dards, but it was con­ceiv­able only be­cause the west­ward dis­tance — or the num­ber of de­grees of the cir­cu­lar route — was imag­ined as far less than it is in re­al­ity.

By a won­der­ful co­in­ci­dence, there is an arte­fact that may give us some idea of what Colum­bus was an­tic­i­pat­ing. The ear­li­est sur­viv­ing ter­res­trial globe of mod­ern times is held in the Ger­man­is­ches Na­tional­mu­seum in Nurem­berg. It was made in 1492 and com­pleted be­fore Colum­bus re­turned in early 1493 with news of his ex­tra­or­di­nary dis­cov­ery. The dis­tance be­tween Europe and the Chi­nese coast looks roughly com­pa­ra­ble to that be­tween Europe and North Amer­ica, and var­i­ous is­lands, in­clud­ing Ja­pan (Ci­pangu) are much closer.

Martin Be­haim’s globe gives us a vivid idea of the state of ge­o­graph­i­cal knowl­edge at the time, and shows it was en­tirely plau­si­ble to pos­tu­late a west­ward short­cut to Asia, even if cross­ing a vast tract of open ocean re­mained ex­tremely danger­ous. And it si­mul­ta­ne­ously makes the dif­fi­culty of es­ti­mat­ing lon­gi­tude dra­mat­i­cally clear.

Euro­pean mar­itime com­merce boomed in the cen­turies fol­low­ing Colum­bus’s voy­age, dom­i­nated by the Span­ish and Por­tuguese in the 16th cen­tury, by the Dutch in the 17th and by the Bri­tish from the 18th. It was the Bri­tish, now equipped with the in­tel­lec­tual re­sources of

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