您现在的位置: 首页 > 英语听力 > 媒体资讯 > 60秒科学 > 正文

60秒科学:质量标准,不标准

时间:2011-01-26 10:17:22 来源:scientificamerican 编辑:sunny  每天三分钟英语轻松学

千克原器是测量质量的标准,它是一个铂铱合金的圆柱体砝码,但经年累月,这个砝码的质量轻了50微克,虽然对人们的日常生活几乎无影响,但对科学界来说却是个引人深思的问题。

In a laboratory vault outside Paris is a small cylinder of platinum–iridium alloy that serves as the standard for all mass measurements worldwide. By an 1889 international accord, the mass of this metal cylinder defines the kilogram.

But that may soon change. The kilogram is the only unit of measurement still based on a man-made artifact. A second of time, for instance, is now defined in terms of an electron transition of the cesium atom. And the meter is tied to the speed of light. Those standards are universal and unchanging—unlike the official kilogram. The reference cylinder's mass has drifted slightly through the years—not enough to throw off your bathroom scale, but enough to bother measurement scientists.

Some of them are meeting January 24th at the Royal Society in London to discuss future improvements to the measurement units. The plan is to eventually relate the kilogram to a universal number known as Planck's constant. But the technology needed to do that is not yet fully developed. So, for the time being, that little metal cylinder outside Paris will just have to keep pulling its weight. I mean, mass.

--John Matson

收藏

相关热词搜索: 60秒科学

上一篇:中美两国元首在白宫国宴上的致辞

下一篇:可可商务英语课堂 第2期:商业午餐

您可能还感兴趣的文章

60秒科学:安慰剂的"安慰"作用
听力练习给病人吃药,并告诉他这是安慰剂,这样的病患仍比未接受治疗的病患有较高程度的改善。They say medicine is as much an art as a science. But sometimes it see

时间:2010-12-27 编辑:sunny

60秒科学:太阳附近的另一个椭圆轨迹
听力练习地球绕太阳椭圆轨道公转和自转的说明。 Happy New Year! And don't feel bad about taking today off. After all, you've traveled far. And I'm not talking ab

时间:2011-01-05 编辑:sunny

60秒科学:Dogs Can't Smell a Liar
Dogs Can't Smell a LiarA study in the journal Behavioural Processes finds that dogs cannot reliably tell if someone is fibbing to them. Karen Hopkin reports Yo

时间:2009-10-31 编辑:alex

60秒科学:Artificial Muscle Brings Back Blink
Artificial Muscle Brings Back BlinkA study in the Archives of Facial Plastic Surgery reports the development of an artificial muscle system that could restore

时间:2010-01-20 编辑:echo

最新文章

无觅相关文章插件,快速提升流量