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K-V-L: Kínverskir töfrar hvöttu evrópska sæfara

Kínverskir töfrar hvöttu evrópska sæfara

Úr tímaritinu Sagan öll 2 tbl. 2010. Eftir Magnus Västerbro.

 

Á síðari hluta 13. aldar olli áttavitinn byltingu í siglingum í Evrópu. Uppfinningar hans er þó að leita alllangt frá ströndum Miðjarðarhafs.

Á torgi einu í hafnarbænum Amalfi á Ítalíu stendur vegleg stytta úr bronsi. Hún er af húfubúnum manni með tæki í höndunum og virðir hann það vandlega fyrir sér. Á styttunni stendur: „Frá Amalfibæ til Flavios Giola, hann fann áttavitann upp“.  Vandinn er bara að þarna eru tvær meinlegar villur.

Í fyrsta lagi var sennilega aldrei uppi maður sem hét Flavio Giola. Nafnið er byggt á misskilningi í seinni tíma heimildum. En hvað svo sem maðurinn hét þá fann hann í öðru lagi ekki áttavitann upp. Tækniundur þetta er mun eldra og ættað úr allt öðrum heimshluta. Eins og svo margar merkilegar uppfinningar á áttavitinn nefnilega rætur að rekja til Kína.

Langt aftur í grárri forneskju voru menn víða um veröldina heillaðir af töfrum segulmagns í sumum hlutum. Platón og Aristóteles lýsa báðir hvernig segulmagnaðir hlutir dragi til sín járn og margir fleiri tjáðu sig um töframátt segulsins.

Austur í Kína urðu menn þó fyrstir til að nýta sér eiginleika segulsins. Í heimildum frá 5. öld f.Kr. segir hvernig nota mætti „suðurvísi“ til að villast ekki af leið á löngum göngum í stóru landi.

Á þessum frumstæða, kínverska áttavita lá léttur en segulmagnaður vísir eða nál á bronsdiski. Vísirinn hreyfðist auðveldlega á diskinum og beindist ævinlega í suður en það þótti Kínverjum í meira lagi guðdómleg átt um þær mundir.

Í hinum vestræna heimi hefur því hins vegar iðulega verið haldið fram að Kínverjum hafi ekki nýst þessi frumstæði suðurvísir til nokkurs hlutar, nema þá helst spádóma og í feng shui. Þá er rétt að minna á þann leiða vana sagnaritara í Evrópu að gera alltaf sem minnst úr hverri þróun sem orðið hefur annars staðar í veröldinni en heima hjá þeim.

Ljóst er að austur í Kína varð mönnum smám saman kunnugt um hina töfrandi eiginleika segulmagnsins. Á 8. öld okkar tímatals kunnu Kínverjar til dæmis að smíða sér járnnálar og gefa þeim segulmagn með því að nudda þeim við segul. Svo fleyttu þeir nálunum á vatni og þar var þá til orðinn fyrirmyndaráttaviti. Samkvæmt þróaðri útgáfu þeirrar uppfinningar mátti hengja segulmagnaðar nálar í þræði og glöggva sig þannig á áttunum.

Sennilega hafa miðaldamenn í Evrópu frétt af tilraunum Kínverja því þeir þróuðu sínar útgáfur.

Uppfinningin er fyrst nefnd í handriti frá 12. öld en margir sagnfræðingar telja að þá hafi notkun þeirra verið þekkt nokkuð lengi.

Ekki má heldur gleyma þeim sæfarendum sem lögðu upp í heimskönnun frá Ítalíu á 12. öld, hvort sem það var frá Amalfi eða annarri hafnarborg eða bæ. Þeir gátu heldur betur nýtt sér eiginleika áttavitans og til urðu tæki sem líkjast meira nútímaáttavitum en þeim útbúnaði sem Kínverjar þekktu. Áttaviti sæfaranna var eins og askur í laginu. Í honum var vísir tengdur skífu með áttamerkjunum og var heiminum skipt í 16 áttir  eða 360 gráður.

Þessi nokkuð frumstæði áttaviti auðveldaði evrópskum sæförum siglingarnar mjög. Áður en langt um leið hættu ítalskir skipstjórar að leggja skipum sínum um hávetur.

Nú gátu þeir með hjálp áttavitans siglt í örugga höfn þrátt fyrir óvænta vetrarstorma.

Mikill skriður komst á siglingar og verslun við Miðjarðarhaf. Gróðinn streymdi hratt og örugglega í kistur verslunarborganna á Ítalíu.

Ekki er vitað hvort kínverskir sæfarendur nýttu sér áttavita á þessum tíma. Í kínverskum handritum virðist þeim tekið sem sjálfsögðum hlutum og notkun þeirra því ekki skráð sérstaklega og við bætist að ekki er til mikið af heimildum um áttavita í Kína á miðöldum. Marco Polo sá ekki ástæðu til að nefna reynslu sína af kínverskum áttavitum í lok 13. aldar. Áttavitinn varð svo enn mikilvægari þegar evrópskir sæfarendur hófu að kanna heiminn á 15. og 16. öld. Áttavitinn gerði Kristófer Kólumbus og Vasco da Gama kleift að rannsaka heiminn og leggja grunninn að yfirráðum Evrópumanna á heimshöfunum.


 

Síðast breytt: rijudagur, 2 gst 2011, 04:59 eh