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  3. Following Nature’s Signposts For many, "navigation" has come to mean the use of navigational instruments and maps. However,

Following Nature’s Signposts For many, "navigation" has come to mean the use of navigational instruments and maps. However,

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问题                         Following Nature’s Signposts
    For many, "navigation" has come to mean the use of navigational instruments and maps. However, even the most basic of these instruments were only invented during the past 2 000 years, by which time humans had already shown a great tendency to travel large distances, and most of the world had already been explored.
    The ability to shape a journey without instruments has a name: "natural navigation". Our ancestors mastered methods of finding their way that depended on their ability to read a variety of natural clues. This is an art borne of an era when there were no alternatives. Evidence of its use can often be found in myths. The long journey is a rich source, with numerous references to the relationship between the sun, stars and direction.
Over Land and Sea
    Familiarity with a landscape is the most prevalent form of natural navigation. In the Sahara, the Tuareg (柏柏尔人) tend goats from an early age. They are given clear guidelines as to the range within which they and the goats are allowed to go. This area is then extended steadily in order to shape the herders’ instincts. Over time, they learn to find their way over a large area without any formal training in the art of navigation.
    The contemporary natural navigator can begin to unlock the potential of the sun with little more than a stick, using shadows to trace its annual and daily patterns. Once the sun’s patterns in the sky have been brought down to Earth and understood, it becomes possible to use the sun even when it isn’t visible. This is because many living things reflect the sun’s arc in some way, even humans: population density across the world is a clue to the sun’s habits.
    But it’s the sunlight-dependent green plants that give the most useful clues. For example, trees act as a memory store for the way in which the sun has shaped their growth. If one side of an isolated deciduous (落叶的) tree appears heavier than the other, then there’s a good chance that this side has received greater levels of sunlight. In the Northern Hemisphere, this is likely to be the southern side.
    The art isn’t limited to land and sky. but has a strong heritage at sea too. The great natural navigators of the Pacific Micronesian islands have learned to read and interpret the different effects of the wind on water. They have come to discern the differences between the instant effect of ripples, the cumulative effect of waves and, most importantly, the sets of swell that march across the ocean with the prevailing seasonal winds. They see and feel these patterns and they can even tell where they are in the ocean from the way in which these swells reflect and refract (折射) around their islands. Through experience, they build a mental map of the way in which the water moves in the ocean. They add to this the varying colors of the sea, the shape and color of the clouds that form over islands, and the way in which the birds behave.
    The key to natural navigation is always remembering that very little in what we see in nature is random. This is the exciting but terrifying truth in natural navigation: it requires such a broad scan of time and distance on every journey, from feeling the wind on your face to reading the shapes of mountain ranges, all the while thinking about forces acting over minutes or millennia.
Connecting With Nature
    It’s the great journeys and explorers that brought navigation to the fore in the past, but there’s no need to undertake formidable expeditions to use natural navigation—it can even be used in towns, where the patterns of buildings, the behavior of people, the motion of clouds overhead and the colors of stone can all yield clues and provoke thought.
    Although it’s sometimes a (tauntingly (令人生畏地) diverse subject, natural navigation is also an extremely accessible, affordable and zero-impact way of connecting with the natural world. It’s a rare and often challenging art, but one that can enrich any journey.
Using the Wind
    The wind can, of course* blow from any direction, but most places will have one or two prevailing wind directions. Exposed trees will show a combing across their extremities, and once the prevailing wind for an area is understood, this combing can be used to deduce direction.
    In the UK, the prevailing winds usually blow from the southwest. On ridges and other exposed areas, this can give an instant reading of direction, just work out from which way the tree appears to have been blown and you have a clue to the direction of southwest.
Using the Land
    The first key to using the land is finding and then getting to know the character of the high ground, which will tell a story of geological formation and erosion, while also offering the best perspective of the landscape.
    For example, the South Downs of Great Britain form a range that runs broadly west to east, near parallel to the south coast. Once this alignment has been observed, it’s easy to make simple deductions. If the sea can be seen, then there must be some south in the view, but if the land slopes away continuously to low country, it must be close to north. To the east and west, the ridge continues across rolling summits without losing height.
Using the Sun
    There are three critical moments in the sun’s arc for natural navigation: sunrise, midday and sunset. If you placed a stick in the ground and marked the tip of its shadow over the course of a day and then at different times of year, you would notice that the shortest shadow on a given day forms a perfect north-south line. The sun is due south from the UK at midday—that is, when the sun is highest in the sky—every day of the year.
    Perhaps more surprisingly, you would begin to notice how much the bearing of sunrise and sunset varies over the course of a year. In the UK in midwinter, the sun rises in the southeast and sets in the southwest. In midsummer, it rises in the northeast and sets in the northwest. There is a 90’ difference between the direction of sunrise in summer and winter; more if you travel north of the UK and less as you head towards the equator.
Using the Stars
    The easiest way to find direction using the stars in the Northern Hemisphere is to use the Plough (北斗七星) to find Polaris, the North Star. First, find the Plough (also known as the Big Dipper or the "saucepan"). This large group of seven stars is easily recognized in the northern half of the sky, both from its distinctive shape and because each star is bright.
    Its shape never changes, although it can appear on its side or even upside down. Next, identify the two "pointer stars". These are the stars that a liquid would run off if you tipped up the "saucepan". Now visually measure the distance between the pointer stars and look along them to a point in the sky five times that distance beyond them. The star on its own in that part of the sky is the North Star. The point on the horizon directly below that star is due north. But note, the North Star isn’t the brightest star in the sky.
The Plough is used in the Northern Hemisphere to find Polaris because it is easily recognized for ______.
选项
答案its distinctive shape and brightness
解析 细节辨认题。最后一个小标题指出，北半球的人通常利用北斗七星找到北极星。根据定位信息可知，这是因为北斗七星因其特别的形状和亮度而容易辨认。
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