在那七个基础单位中,有六个取决于自然界中的恒定物体:安培,坎德拉,秒,米,开氏度以及摩尔。
The kilogram is unique in that it is defined by reference to a lump of crude, man-madestuff.
唯独只有千克单位取决于未加工的人造金属块。
Besides aesthetic niggles, that fact leads to an important practical problem.
除了一些美学上的吹毛求疵,这一事实还引出了一个重要的实际问题。
The international prototype kilogram, the technical name for the cylinder in Sevres, doesnot in fact keep a constant mass.
事实上,国际千克原器的重量并不是恒定的。
Over the years pollutants from the air settle on its surface, causing its mass to rise.
这些年来,空气中的污染物落在这个金属块表面,增加了其重量。
Attempts to clean it then cause its mass to fall.
而试图清洁其表面又会减少其重量。
As a result, what science understands by a kilogram has varied, but has done so in a waythat is, by definition, unmeasurable.
结果导致千克单位的科学定义变了,根据这样的定义,千克是无法测量出来的。
A clean sweep?
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