科学美国人60秒:磁场或为候鸟导航-托福听力下载

　　科学美国人60秒中文翻译：

　　If you're lost, you need a map and a compass. 如果你迷路了，就需要地图和指南针。

　　The map pinpoints where you are, and the compass orients you in the right direction. 地图会标明你所处位置，而指南针则能指引正确的方向。

　　Migratory birds, on the other hand, cantraverse entire hemispheres and end up just a couple miles from where they bred last year, using their senses alone. 而候鸟仅仅通过感知就能横跨整个半球，最后在去年繁殖几公里远的地方落脚。

　　Their compass is the Sun, the stars and the Earth's magnetic field. 它们的指南针是太阳，星星及地球的磁场。

　　But their map is a little more mysterious. 但是它们的地图更具神秘色彩。

　　One theory goes that they use olfactory cues—how a place smells. 有的理论认为它们是通过嗅觉器官，闻一个地方的气味断定。

　　Another is that they rely on their sense of magnetism. 而其它则认为候鸟依赖的是自身对磁场的感知。

　　Researchers in Russia investigated the map issue in a past study by capturing Eurasian reed warblers on the Baltic Sea as they flew northeast towards their breeding grounds near Saint Petersburg. 曾进行的一项研究中俄罗斯科学家们通过抓获在波罗的海飞往东北部圣彼得堡附近繁殖地时欧亚芦苇莺对候鸟们所使用的地图进行了调查。

　　They moved the birds 600 miles east, near Moscow. 他们将这些鸟类向东移动600英里,临近莫斯科。

　　And the birds just reoriented themselves to the northwest—correctly determining their new position. 结果这些候鸟正确地判定自己的新方位，重新将位置调整至西北方。

　　Now the same scientists have repeated that experiment—only this time, they didn't move the birds at all. 而现在同样的科学家们又重复进行了上述实验—只是这一次，他们没有移动候鸟的位置。

　　They just put them in cages that simulated the magnetic field of Moscow, while still allowing the birds to experience the sun, stars and smells of the Baltic. 他们只是将候鸟们关进模拟莫斯科磁场的笼子里，而在这样的环境下候鸟们仍可以感受到阳光、星星及波罗的海的气味。

　　Once again, the birds re-oriented themselves to the northwest 结果这些候鸟再一次重新将位置调整至西北方。

　　suggesting that the magnetic field alone—regardless of smells or other cues, is enough to alter the birds' mental map. 这表明忽略气味以及其它要素仅磁场本身就足以改变鸟类心中的地图。

　　The study is in the journal Current Biology. 这项研究已经在《现代生物学》杂志上发表。

　　And if you're envious of that sixth sense—keep in mind that since the Earth's magnetic field fluctuates, the researchers say magnetic route-finding is best for crude navigation. 如果你还在嫉妒别人的第六感—记住科学家们表示自地球磁场发生波动以来，磁导航最适合寻找原油勘探。

　　Meaning for door-to-door directions—you're still better off with your GPS. 如果希望准确定位，你最好还是带上GPS。

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