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During experiments at the Bimini Biological Research Station in the Bahamas, researchers Eric Stroud and Michael Hermann dropped a small magnet in the water beside a shark. The presence of the magnet elicited a distinct reaction from the fishthey darted away from it.
Why the intense reaction? The interaction of salt water and charged metals produces a weak electrical field(电场). When a shark comes close to that field, the field seems to disrupt the sharks‘ special sixth sense, electroreception(电感受). Many shark species have pores dotted around their snouts called ampullae of Lorenzini(洛仑兹壶腹，鲨鱼用它来感受电场信号)that detect minute changes of electricity in the seawater, up to one-billionth of a volt. These electrical impulses come from the tiniest muscle contractions of other aquatic life formsor peopleand are carried through the ions in the salt water.
What does salt water have to do with electricity? Salt water is an ionic solution, meaning it contains particles with unpaired electrons. Because of this quality, salt water can also act as an electrical conductor(导电体). When a charged magnet comes into contact with salt water, the ions flow through the metal to become stabilized, resulting in the electrical field. We know that sharks can sense shifts in the surrounding underwater electrical fields through their ampullae of Lorenzini. Running into these stronger electric fields...
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Recent discoveries in New World archaeology along with new scientific methods for analyzing data have led to new ideas regarding the origin of the first peoples of the Americas and their time of arrival.
The traditional theory held that the first Americans crossed the land bridge from Siberia to Alaska around 11,500 years ago and followed an "ice-free corridor" between two large Canadian ice sheets (the Laurentide and Cordilleran) to reach unglaciated lands to the south. These first inhabitants, whose archaeological sites are scattered across North and South America, were called the Clovis people, named after the town in New Mexico where their fluted spear points used for hunting mammoth were first found in 1932.
旧观点：11500年前越冰南下，这些第一批定居者散布在南北美洲，叫做Clovis人。
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