科学技术

　　Measurement

　　测量

　　Mass effect

　　质量效应

　　A better way to clean the world's one true kilogram

　　清洁世界上真正一千克的更好方法

　　IN SEVRES, on the outskirts of Paris, sealed beneath a triplet of bell jars in the laboratories of the Bureau International des Poids et Mesures, sits a small cylinder of platinum-iridium alloy.

　　在位于巴黎郊区的塞夫勒市，国际计量局实验室里，一个三层的钟形器皿里密封着一个铂铱合金制成的小圆柱。

　　Put it on a scale, and it would weigh 1 kilogram—which is appropriate, since this lump of metal is not just a kilogram but The Kilogram, the ultimate reference standard for the way the Systeme internationale d'unites measures mass.

　　给这个小圆筒称重，你会发现它重1千克，这个重量刚刚好，因为这个金属块不只代表1千克，而代表着千克单位，是国际单位体系中测重的最终参考标准。

　　Scientists like the metric system partly for its simplicity—everything is based on powers of ten, which makes calculation easy—and partly for the elegance of its foundations.

　　科学家亲睐公制的部分原因在于其简洁性，即任何物品以十为进制进行测量，方便运算；还有部分原因在于其成立基础很好。

　　Of its seven fundamental units, six are defined with reference to unvarying constants of nature: the ampere, the candela, the second, the metre, the kelvin and the mole.

　　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-made stuff.

　　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, does not 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 way that 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?

　　擦干净了没？

　　The cleaning that attempts to keep the kilogram constant is done by a member of staff at the bureau, using a combination of steam and a chamois-leather cloth soaked in ethanol and ether.

　　试图保持金属块重量恒定的清洁任务由国际计量局员工来做，用蒸汽和浸泡过含乙醇溶液的油鞣革布来进行清洁。

　　But given the sensitivity of modern instruments, which can detect gains or losses of the order of billionths of a kilogram, it must be done properly.

　　但鉴于现代工具测量十分精细，物体重量增减十亿分之一千克都可以测出来，这项清洁工作必须谨慎执行。

　　Too gentle a rubdown leaves contaminants on the surface. Too vigorous a scrubbing erodes the metal itself.

　　擦拭太过温柔，其表面会留有污染物；用力过猛，又会擦掉金属本身的表面成分。

　　Worse, the IRK is not the only such cylinder in the world.

　　更糟的是，国际千克原器并不是这个世界上唯一的此类圆柱体。

　　Dozens of replicas exist in official laboratories in many countries.

　　还有几十个类似的复制品存放在许多其他国家的官方实验室里。

　　Each must be cleaned to the same exacting standards if it is to remain a true copy of the French original.

　　如果每个都要和法国原件那个如假包换的话，那么每个圆柱体都要被清洁得和现有法国标准一样重。

　　In practice, that has often meant shipping the whole lot back to France so that the same person can scrub them all down.

　　那样实际做起来就是要把别国圆柱体运到法国去，由同样的人来做擦拭工作。

　　Now, though, Peter Cumpson and Naoko Sano, a pair of researchers at the University of Newcastle, in England, reckon they have come up with a better way.

　　然而现在，英国纽卡斯尔大学的皮特·坎普森和 佐野直之认为他们想出了更好的清洁方法。

　　In a paper just published in Metrologia, they describe the results of a method that combines traditional washing with a technique adapted from the chip-manufacturing business, which employs a combination of ultraviolet light and the ozone that such light synthesises from the air to strip pollutants away.

　　前不久他们在《计量学》上发表论文说，传统清洁方法加上紫外线和臭氧这种合成光可以清洁掉金属表面的污染物。

　　The idea of using ultraviolet light was first proposed back in the 1990s, says Dr Cumpson, but has yet to be adopted.

　　采用紫外线这个主意在上世纪九十年代就首次被提出来了，坎普森博士说，但是一直没被采纳。

　　This latest paper, which reports the results of using the method on strips of platinum-iridium alloy, shows that the method does a good job of removing the carbon-based gunk that settles onto the weights from the air.

　　根据这篇最新论文，在铂铱合金条块上进行的实验显示这种方法能够很好地去除增加条块重量的空气碳黏质物。

　　Importantly, says Dr Cumpson, unlike a manual rubdown, his procedure can easily be standardised, and the kit necessary to perform it is cheap and widely available, allowing laboratories around the world to keep their own kilogram replicas clean.

　　重要的是，坎普森博士说，他们的清洁方法是可以标准化的，不像人工擦拭，而且这种方法所涉及的东西既便宜又唾手可得，可以清洁世界上所有实验室的重量单位复制品。

　　It is not, however, perfect.

　　然而这种方法也算不上完美。

　　Besides atmospheric muck, researchers reckon that other things are altering the masses of the world's kilograms.

　　研究人员发现除了空气中积攒下来的脏东西，其他东西也在影响着国际标准千克的重量。

　　One significant effect, says Dr Cumpson, is contamination with mercury.

　　坎普森博士说其中一个关键的影响因素就是水银污染，

　　The likely source is not atmospheric pollutants, but lab accidents.

　　其污染源不是空气污染物，而属于实验室偶然事件。

　　Say you drop a thermometer and it shatters, he says.

　　比如你把一个温度计丢掉地面上，里面的水银散开了，坎普森博士说，

　　A couple of blobs of mercury fall through the floorboards and evaporate slowly over the years. Some of that mercury is then deposited.

　　几滴水银落在地板上，随着时间，慢慢蒸发在空气中，其中一些会沉积。

　　Unlike the atmospheric junk, which simply encrusts the surface, mercury seeps into microscopic flaws in the cylinders' surfaces created by the polishing process.

　　和仅仅落在圆柱表面的空气污染物不同，水银会渗进圆柱体在擦磨过程中表面留下的微小缺陷里。

　　Once it gets in, it's in there for good. You can't remove it, says Dr Cumpson.

　　只要水银渗进去了，它就会永远留在圆柱体里了。你根本无法去除，坎普森博士说。

　　The missing Planck

　　被人遗忘的普朗克

　　It is problems like this—and the fact that the world's kilograms are changing in mass at different rates—that are behind a push to bring the kilogram into line with the rest of the SI, and to define it purely with reference to natural constants.

　　问题就在于此，再加上世界各国的千克标准重量正在以不同速率变化着，这些都敦促千克单位和SI体系下其他单位一样恒定，要在纯粹参考自然界恒量的基础上定义千克。

　　Next year, the International Committee on Weights and Measures will discuss whether to tie it to something called Planck's constant, a number in quantum mechanics that relates the energy level of a photon to its wavelength.

　　明年，国际重量与测量委员会将会讨论是否要将千克和普朗克恒量联系起来，普朗克恒量是指量子力学中联系光子能及其波长的数字。

　　A supersensitive electromechanical scale called a watt balance could then be used to define the kilo with reference to Planck's constant, finally liberating the SI from its reliance on fallible artefacts.

　　测量极其精准的机电天平—瓦特天平可以在参考普朗克恒量的基础上定义千克重量，这就使得SI再不用依赖不精确的人工制品了。

　　That is the theory, at least.

　　以上至少在理论上是成立的。

　　But watt balances are fiendishly complicated bits of kit.

　　但是瓦特天平极其复杂。

　　There are only a handful in the world, a situation that is unlikely to change for the foreseeable future.

　　世界上瓦特天平也为数不多，在可预见的未来，其数量也不会有增减。

　　This means that, although the kilo will in theory be defined by an abstract constant, in practice so-called transfer standards will still be needed for the many countries without the nous or the cash to run a watt balance of their own.

　　这就意味着即使在理论上可以用抽象恒量来定义千克重量，许多国家在实际操作中还是要用到所谓的可变标准，因为他们本身即没能力也无资金来动用一台瓦特天平。

　　Translated into English, the upshot is that outside the most advanced countries, lumps of metal will continue to be used to define the kilo—although they will probably be made of gold, rather than platinum and iridium.

　　简单讲，就是发达国家以外的国家和地区会继续用金属块来定义千克重量，尽管金属块可能用金制成，而非铂铱合金。

　　These will be susceptible to exactly the same sorts of contamination that plague the current generations of kilogram.

　　但金属块重量仍会受到同样的污染。

　　Luckily, Dr Cumpson's method ought to work on them, too.

　　所幸的是，坎普森博士的方法对它们也同样奏效。

　　1.base on 基础上

　　Lance cpl. baker at shir ghazay patrol base on jan. 30.

　　兰斯科普尔贝克在西尔嘎泽巡逻基地。

　　Ms. na said a military base on the island was on fire.

　　na女士说，岛上的一处军事基地着火。

　　2.define with 定义

　　They define those with an income of over$ 50 per day-just 2% of latin americans-as rich.

　　他们将那些日收入达50美元的人只占拉美2%的人口定义为富人。

　　Define decisions with a rationale, then document and communicate those decisions.

　　用基本原理定义决策，并文档化和传达这些决策。

　　3.lead to 领到；通向；导致

　　That can lead to serious consequences.

　　这会导致严重的后果。

　　All these ideologies lead to repression.

　　所有这些思想最终都导致镇压。

　　4.in fact 实际上，其实；实则；事实上

　　Many japanese solar firms are in fact expanding.

　　实际上许多日本太阳能公司正在逐步壮大。

　　In fact there are other models to consider.

　　实际上我们还可以考虑其他一些模式。