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SSS 2009-08-12

时间:2010-05-18 06:11来源:互联网 提供网友:mark@li   字体: [ ]
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You’ve given some thought to oxygen, carbon, uranium. But you’ve probably never mused1 about the element ytterbium, symbol Yb. A new study by scientists at the National Institute of Standards and Technology, or NIST, says that ytterbium could find a role in super-accurate atomic clocks. The report is in the journal Physical Review Letters.

 

The gold standard, if you will, for atomic clocks, is the element cesium, symbol Cs. Official civilian2 time is kept by the cesium NIST-F1 fountain clock, accurate to within one second every 100 million years. And the international definition of the second is based on exactly how many vibrations3 happen when a cesium atom’s electron changes energy levels. How many? 9,192,631,770. Exactly.

 

Anyway, your watch is fine for getting to work about on time, but if you want your GPS to work fine, you need these atomic clocks on Earth and on satellites. And an ytterbium clock has the potential to be even more accurate and stable than the cesium chronometer4. Wow, I gotta go, look at the time.

 


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1 mused 0affe9d5c3a243690cca6d4248d41a85     
v.沉思,冥想( muse的过去式和过去分词 );沉思自语说(某事)
参考例句:
  • \"I wonder if I shall ever see them again, \"he mused. “我不知道是否还可以再见到他们,”他沉思自问。 来自《简明英汉词典》
  • \"Where are we going from here?\" mused one of Rutherford's guests. 卢瑟福的一位客人忍不住说道:‘我们这是在干什么?” 来自英汉非文学 - 科学史
2 civilian uqbzl     
adj.平民的,民用的,民众的
参考例句:
  • There is no reliable information about civilian casualties.关于平民的伤亡还没有确凿的信息。
  • He resigned his commission to take up a civilian job.他辞去军职而从事平民工作。
3 vibrations d94a4ca3e6fa6302ae79121ffdf03b40     
n.摆动( vibration的名词复数 );震动;感受;(偏离平衡位置的)一次性往复振动
参考例句:
  • We could feel the vibrations from the trucks passing outside. 我们可以感到外面卡车经过时的颤动。
  • I am drawn to that girl; I get good vibrations from her. 我被那女孩吸引住了,她使我产生良好的感觉。 来自《简明英汉词典》
4 chronometer CVWyh     
n.精密的计时器
参考例句:
  • Murchison followed with his eye the hand of his chronometer.莫奇生的眼睛追随着他的时计的秒针。
  • My watch is more expensive because it's a chronometer.我的手表是精密型的,所以要比你的贵。
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