The Arctic and the Antarctic are privileged locations for observers interested in understanding how our world is shaped by the forces of nature and the workings of history. These areas have inspired countless humans to undertake epic expeditions of discovery and have witnessed both great triumphs and miserable defeats. As a planetary litmus paper it is at the poles we can detect the effects of natural oscillations and human activities on the global ecosystems.
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019 Compass and Navigation
The magnetic compass has been the most important instrument used for navigation since the beginning of the European voyages of discovery and until satellite positioning was introduced. The principle of functioning is dependent on the magnetic field of the Earth. It is not a recent invention and a form was used for divination in China since 200 BCE. It was used for navigation first in the 11th century in China and probably it was introduced from there to Europe in the 12th century through trade routes. The of the compass for navigation is testified by the effort put by nations to measure the magnetic field of the planet, to determine the position of the magnetic north pole and to investigate its yearly movement. One of the famous expeditions to pursue such investigations was the Franklin voyage in search of the Northwest Passage. The Vikings who navigated areas close to the magnetic pole, which makes the magnetic compass unusable, most probably used a sun-based compass, that could also be used to determine variations in latitude during a voyage, and they might even have been able to use this system in conditions of bad visibility usign a crystal of calcite as polarizing filter. The next revolution for polar navigation came with the invention of the gyrocompass. Nowadays navigation is greatly symplified and made accessible to private and professional users through satellite systems like GPS, GLONASS and GALILEO and BeiDou which can be accessed using dedicated receivers or apps on mobile devices.