Oceans cover almost 71 percent of the Earths surface. Travelers on land can find their way by recognizing landmarks and navigating with the help of maps, but there are no landmarks at sea and mariners must find other signposts to guide them. Many centuries ago, navigators learned to steer by the sun and stars and by compasses that align themselves with the Earths magnetic field. Equipped with simple instruments, surveyors defined the boundaries of the ocean while scientists mapped the ocean currents.
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Oceans cover almost 71 percent of the Earths surface. Travelers on land can find their way by recognizing landmarks and navigating with the help of maps, but there are no landmarks at sea and mariners must find other signposts to guide them. Many centuries ago, navigators learned to steer by the sun and stars and by compasses that align themselves with the Earths magnetic field. Equipped with simple instruments, surveyors defined the boundaries of the ocean while scientists mapped the ocean currents.
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