BASE UNITS 基本单位
The International System has base units from which all others in the system are derived. The standards for the base units, except for the kilogram, are defined by unchanging and reproducible physical occurrences. For example, the meter is defined as the distance traveled by light in a vacuum in 1/299,792,458 of a second. The standard for the kilogram is a platinum-iridium cylinder kept at the International Bureau of Weights and Standards in Sevres, France.
国际制度有基本单位，由此衍生出此制度中的其他单位。除千克以外，基本单位的标准以不变的且可再生的物理事件为解释。例如，公尺被解释为光在真空中以每1/299,792,458秒的速度所穿越的距离。千克的标准是指置于法国塞夫勒的国际度量及标准局的白金铱圆柱为准。
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