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Researchers Weigh Benefits of a New Kilogram Standard

質(zhì)量標(biāo)準(zhǔn)，不標(biāo)準(zhǔn)

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.

巴黎城外的一個(gè)玻璃罩里存放著一個(gè)鉑銥合金圓柱體，這個(gè)圓柱體就是全世界測(cè)量物體質(zhì)量的參照標(biāo)準(zhǔn)。1889年某項(xiàng)國際協(xié)議中規(guī)定，該鉑銥合金圓柱體的質(zhì)量為1千克。

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.

但這個(gè)標(biāo)準(zhǔn)即將成為過去。千克是目前唯一一個(gè)以人工制品為參照標(biāo)準(zhǔn)的計(jì)量單位。比如說，秒就是根據(jù)銫原子內(nèi)部的電子躍遷時(shí)間來的下定義，而米的定義則和光速有關(guān)。這些計(jì)量標(biāo)準(zhǔn)普遍通用、亙古不變，而千克的參照標(biāo)準(zhǔn)則不然。歷經(jīng)多年，質(zhì)量標(biāo)準(zhǔn)參照物——鉑銥合金圓柱體的質(zhì)量已略有減輕。你倒不至于把浴室秤給扔掉，但計(jì)量學(xué)家就有得操心了。

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.

部分計(jì)量學(xué)家將于1月24日在英國皇家學(xué)會(huì)舉行會(huì)議探討計(jì)量標(biāo)準(zhǔn)的改善問題，計(jì)劃最終將千克這個(gè)計(jì)量單位與普朗克常數(shù)聯(lián)系起來。然而，要完成這項(xiàng)工作，技術(shù)問題仍有待解決。因此，在此之前，那小小的合金圓柱體還得繼續(xù)扮演“重量”級(jí)的角色，當(dāng)然，是在質(zhì)量測(cè)量方面的重量級(jí)角色。

--John Matson

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