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Contributos portugueses para o conhecimento do magnetismo terrestre no século XIX
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A história da navegação está bem marcada pelo magnetismo terreste. A
utilização da agulha magnética no Mediterrâneo remonta, pelo menos, ao século XIII.
No início do século XVI, os portugueses tomaram consciência das potencialidades
da declinação magnética nos vastos espaços marítimos que percorriam. Perante o
problema da longitude, foram coligindo informação da declinação e desenvolvendo
conhecimento em torno das questões a ela associada, de forma pioneira. A relevância
da declinação para a navegação perdurou até ao século XX.
O conhecimento da origem do geomagnetismo e, consequentemente, o
refinamento da predição das suas componentes sofreu, a partir do século XIX, grandes
desenvolvimentos científicos. As questões em aberto careciam da obtenção e
comparação de dados das componentes magnéticas e respetivas variações à escala
global.
Inglaterra, a grande potência da época, viria a assumir, em meados do século XIX,
a liderança do processo das observações magnéticas simultâneas e o processamento
dos avultadíssimos dados recolhidos, beneficiando da sua dianteira tecnológica e dos
vastos territórios ultramarinos, para conduzir essas observações em pontos
estratégicos.
Portugal, nessa altura, adere a esse movimento científico, na sequência da
estabilização do país na segunda metade do século. As duas principais instituições de
ensino superior, de Coimbra e Lisboa, onde residia o conhecimento científico, viriam a
ter um papel central nesse processo, tendo suscitado a criação dos primeiros
observatórios meteorológicos e magnéticos nacionais. A relação privilegiada com
Inglaterra foi muito profícua e insubstituível. Em todo este processo, João Brito Capelo
e Jacinto de Sousa assumiram uma especial relevância. O campo magnético terrestre
passou a ser monitorizado em permanência e as observações foram estendidas aos
territórios ultramarinos de África.
The history of navigation is marked by terrestrial magnetism. The use of the magnetic needle in the Mediterranean dates back at least to the 13th century. At the beginning of the 16th century, the Portuguese became aware of the potential of magnetic declination in the vast maritime spaces they traveled through. Faced with the problem of longitude, they collected information on declination and developed knowledge around the issues associated with it, in a pioneering way. The relevance of declination for navigation lasted until the 20th century. The knowledge of the origin of geomagnetism and, consequently, the refinement of the prediction of its components underwent, from the 19th century onwards, major scientific developments. The open questions required the collection and comparison of data on magnetic components and respective variations on a global scale. In the mid-nineteenth century, the great power of the time assumed the leadership of the process of simultaneous magnetic observations and the processing of the huge amounts of data collected, benefiting from its technological forefront and vast overseas territories, to conduct these observations at strategic points. Portugal, at that time, joined this scientific movement, following the country's political stabilization in the second half of the century. The two main higher education institutions, at Coimbra and Lisbon, where scientific knowledge resided, would play a central role in this process, given rise to the creation of the first national meteorological and magnetic observatories. The privileged relationship with England was very fruitful and irreplaceable. Throughout this process, João Brito Capelo and Jacinto de Sousa assumed a special relevance. The terrestrial magnetic field was permanently monitored, and observations were extended to the overseas territories of Africa.
The history of navigation is marked by terrestrial magnetism. The use of the magnetic needle in the Mediterranean dates back at least to the 13th century. At the beginning of the 16th century, the Portuguese became aware of the potential of magnetic declination in the vast maritime spaces they traveled through. Faced with the problem of longitude, they collected information on declination and developed knowledge around the issues associated with it, in a pioneering way. The relevance of declination for navigation lasted until the 20th century. The knowledge of the origin of geomagnetism and, consequently, the refinement of the prediction of its components underwent, from the 19th century onwards, major scientific developments. The open questions required the collection and comparison of data on magnetic components and respective variations on a global scale. In the mid-nineteenth century, the great power of the time assumed the leadership of the process of simultaneous magnetic observations and the processing of the huge amounts of data collected, benefiting from its technological forefront and vast overseas territories, to conduct these observations at strategic points. Portugal, at that time, joined this scientific movement, following the country's political stabilization in the second half of the century. The two main higher education institutions, at Coimbra and Lisbon, where scientific knowledge resided, would play a central role in this process, given rise to the creation of the first national meteorological and magnetic observatories. The privileged relationship with England was very fruitful and irreplaceable. Throughout this process, João Brito Capelo and Jacinto de Sousa assumed a special relevance. The terrestrial magnetic field was permanently monitored, and observations were extended to the overseas territories of Africa.