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由于现行米定义的复现精度已不能适应现代科学技术发展的需要,因而最近召开的国际计量委员会审议了由起草米定义的联合工作组所提出的报告,并且决定将更改米定义的具体建议提交1983年即将召开的国际计量大会批准实行。自从1889年通过“米的长度等于米原器两端刻线间的距离”这一定义以来,1960年曾作了第一次更改,当时把米定义更改为:“米的长度等于氪86原子的2P_(10)和5d_5能级之间跃迁所对应的辐射在真空中波长的1650763.73倍”。1983年即将实行的米定义改为:“米是光在真空中1/299792458秒时间间隔内所行进路程的长度”。米定义的第一次更改废除了米的实物基准(米原器);这一次的更改则不仅废除了米的自然基
Since the current precision of the definition of rice has been unable to meet the needs of the development of modern science and technology, the recently-convened International Metrology Committee reviewed the report submitted by the joint working group defined by the drafting of rice and decided to submit the specific proposal to change the definition of rice. The International Metrology Conference to be held in 1983 approved the implementation. Since the 1889 definition of “the length of rice equals the distance between the reticle lines at both ends of the original device”, the first change was made in 1960 when the definition of rice was changed to read: “The length of rice is equal to 氪86 atoms. The radiation corresponding to the transition between the 2P_(10) and 5d_5 levels is 1,650,763.93 times the wavelength in the vacuum.“ The definition of rice to be implemented in 1983 was changed to: ”Rice is the length of light travelled in a vacuum in a time interval of 1/299792458 seconds." The first change in the definition of rice abolished the physical basis of rice (the original rice); this change not only abolished the natural basis of rice.