2015职称英语理工类考试阅读理解文章及练习Snowflakes：文章
<p> <span word="Snowflakes">Snowflakes</span></p><p> <span word="Youve">Youve</span> <span word="probably">probably</span> <span word="heard">heard</span> <span word="that">that</span> <span word="no">no</span> <span word="two">two</span> <span word="snowflakes">snowflakes</span> <span word="are">are</span> <span word="alike">alike</span>.<span word="Of">Of</span> <span word="course">course</span>,<span word="nobody">nobody</span> <span word="has">has</span> <span word="ever">ever</span> <span word="confirmed">confirmed</span> <span word="that">that</span> <span word="statement">statement</span> <span word="by">by</span> <span word="examining">examining</span> <span word="every">every</span> <span word="one">one</span> <span word="of">of</span> <span word="the">the</span> <span word="estimated">estimated</span> <span word="one">one</span> <span word="septillion">septillion</span> <span word="snowflakes">snowflakes</span> <span word="that">that</span> <span word="drift">drift</span> <span word="to">to</span> <span word="Earth">Earth</span> <span word="each">each</span> <span word="year">year</span>.<span word="still">still</span>,<span word="Kenneth">Kenneth</span> <span word="Libbrecht">Libbrecht</span>,<span word="a">a</span> <span word="professor">professor</span> <span word="at">at</span> <span word="the">the</span> <span word="California">California</span> <span word="Institute">Institute</span> <span word="of">of</span> <span word="Technology">Technology</span>,<span word="is">is</span> <span word="confident">confident</span> <span word="that">that</span> <span word="the">the</span> <span word="statement">statement</span> <span word="is">is</span> <span word="true">true</span>.</p><p> <span word="Snowflakes">Snowflakes</span> arent flaky,says Libbrecht.At their basic level,theyre crystalline.The lattice of every snowflake is six-sided in shape.The simplest snow crystals are six-sided flat plates and six-sided columns.Such crystals are common in places where the air is extremely cold and dry.Snow crystals acquire their special beauty when their simple six-sided symmetry blossoms.Under the right conditions,each of the six corners of a crystal sprouts what is called an arm.In a matter of minutes,the arms can become highly ornate and give the crystal a star like appearance.</p><p> <span word="Several">Several</span> <span word="factors">factors</span> <span word="in">in</span> <span word="the">the</span> <span word="environment">environment</span> <span word="affect">affect</span> <span word="the">the</span> <span word="shape">shape</span> <span word="and">and</span> <span word="growth">growth</span> <span word="rate">rate</span> <span word="of">of</span> <span word="a">a</span> <span word="snow">snow</span> <span word="crystal">crystal</span>.<span word="One">One</span> <span word="factor">factor</span> <span word="is">is</span> <span word="humidity">humidity</span>.<span word="Crystals">Crystals</span> <span word="grow">grow</span> <span word="faster">faster</span> <span word="and">and</span> <span word="in">in</span> <span word="more">more</span> <span word="intricate">intricate</span> <span word="shape">shape</span> <span word="as">as</span> <span word="humidity">humidity</span> <span word="increases">increases</span>.<span word="A">A</span> <span word="second">second</span> <span word="factor">factor</span> <span word="is">is</span> <span word="air">air</span> <span word="temperature">temperature</span>.<span word="A">A</span> <span word="snowflake">snowflake</span> <span word="is">is</span> <span word="born">born</span> <span word="when">when</span> <span word="several">several</span> <span word="molecules">molecules</span> <span word="of">of</span> <span word="water">water</span> <span word="vapor">vapor</span> <span word="in">in</span> <span word="a">a</span> <span word="could">could</span> <span word="land">land</span> <span word="on">on</span> <span word="a">a</span> <span word="speck">speck</span> <span word="of">of</span> <span word="dust">dust</span> <span word="and">and</span> <span word="freeze">freeze</span> <span word="to">to</span> <span word="form">form</span> <span word="a">a</span> <span word="simple">simple</span> <span word="crystal">crystal</span>.<span word="As">As</span> <span word="the">the</span> <span word="young">young</span> <span word="crystal">crystal</span> <span word="bops">bops</span> <span word="around">around</span> <span word="in">in</span> <span word="the">the</span> <span word="cloud">cloud</span>,<span word="it">it</span> <span word="passes">passes</span> <span word="through">through</span> <span word="air">air</span> <span word="pockets">pockets</span> <span word="of">of</span> <span word="varying">varying</span> <span word="temperatures">temperatures</span>.<span word="If">If</span> <span word="the">the</span> <span word="crystal">crystal</span> <span word="passes">passes</span> <span word="through">through</span> <span word="a">a</span> <span word="pocket">pocket</span> <span word="of">of</span> <span word="air">air</span> <span word="that">that</span> <span word="is">is</span>,<span word="says">says</span>,15 <span word="degrees">degrees</span> <span word="Celsius">Celsius</span>,<span word="it">it</span> <span word="will">will</span> <span word="grow">grow</span> <span word="quickly">quickly</span> <span word="and">and</span> <span word="sprout">sprout</span> <span word="six">six</span> <span word="arms">arms</span>,<span word="says">says</span> <span word="Libbrecht">Libbrecht</span>.<span word="If">If</span> <span word="the">the</span> <span word="crystal">crystal</span> <span word="is">is</span> <span word="then">then</span> <span word="tossed">tossed</span> <span word="into">into</span> <span word="a">a</span> <span word="warmer">warmer</span> <span word="pocket">pocket</span>,<span word="one">one</span> <span word="about">about</span>-10℃,<span word="the">the</span> <span word="arms">arms</span> <span word="tips">tips</span> <span word="will">will</span> <span word="stop">stop</span> <span word="growing">growing</span> <span word="quickly">quickly</span> <span word="and">and</span> <span word="form">form</span> <span word="six">six</span>-<span word="side">side</span> <span word="plates">plates</span>.<span word="If">If</span> <span word="the">the</span> <span word="crystal">crystal</span> <span word="then">then</span> <span word="drifts">drifts</span> <span word="into">into</span> <span word="an">an</span> <span word="even">even</span> <span word="warmer">warmer</span> <span word="pocket">pocket</span> <span word="of">of</span> <span word="about">about</span> -℃,<span word="its">its</span> <span word="top">top</span> <span word="and">and</span> <span word="bottom">bottom</span> <span word="will">will</span> <span word="grow">grow</span> <span word="more">more</span> <span word="quickly">quickly</span> <span word="than">than</span> <span word="its">its</span> <span word="sides">sides</span> <span word="and">and</span> <span word="become">become</span> <span word="more">more</span> <span word="column">column</span> <span word="like">like</span> <span word="in">in</span> <span word="shape">shape</span>.</p>
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