Historic Kilogram Measure to Be Replaced

 

For nearly 130 years, the world’s scientists have used a singular small, metal cylinder¹ to define the exact weight of a kilogram. But that is about to change.

The cylinder was made in 1889 of platinum² and iridium metals. It is called the Grand K. The International Bureau of Weights and Measures, or BIPM, keeps the object at its headquarters near Paris. Many safeguards protect the Grand K. In fact, it takes three specially³ chosen people to open the container that holds the cylinder. They must each release separate locks at exactly the same time to do so.

The Grand K has served as the official world measurement tool for weight in kilograms. All modern mass measurements have been based on the Grand K.

There are seven main units of official measure. These include the meter for length, and the second for time. Other units measure things like electrical current or amounts of a substance.

Currently, the kilogram is the only measure based on a physical object. The meter used to be represented by a singular metal stick. In 1983, scientists decided⁴ that a meter would be defined by the speed of light. Light speed is constant. Light always takes the same amount of time to travel one meter.

The Grand K was only rarely – and always extremely carefully – removed so that other kilos sent from around the world could be compared to it.

But even such rare contact does not fully⁵ protect the Grand K and its mass. It is still affected⁶ by its environment. This can be a problem when using it as the single exact weight measurement tool.

Ian Robinson is an engineering specialist at Britain’s National Physical Laboratory. He told Reuters that pollutants⁷ in the atmosphere can easily add weight to the historic measuring tool.

“When you just get it out of the vault⁸, it’s slightly dirty,” Robinson said. “But the whole process of cleaning or handling or using the mass can change its mass.”

Now, officials at the BIPM believe the time is right to change the kilogram standard, to make it fit better in today’s technology-driven world. So on November 16, scientists from around the world will gather in Paris to approve replacing the Grand K with a new standard.

BIPM’s director, Martin Milton, told the Associated Press he does not see the event as a sad development, but as “a moment of celebration.” He says this is because it will be the last world measurement standard to “finally be replaced by new innovation.”

The Grand K is to be replaced by a new definition based on a complex physics formula called “Planck’s constant.” This process can measure the mass of an object using electromagnetic force. The method will permit scientists to correctly measure an exact kilogram without comparing it directly with the weight of a physical object.

Milton says changes in drug and chemical production now require new ways to measure much smaller amounts of material. He says a kilo is fine for weighing things like potatoes, where extreme exactness is not necessary.

“But it's not the right weight for many applications in demanding science and industry,” he said.

Scientists have spent years developing the new definition to make sure the change goes smoothly⁹.

Although the time has finally come to change the Grand K, Milton says the system has served humanity well and proved man’s ability to unite for science. “It’s been called a great work of peace, actually, because it’s one of the areas where all of the states of the world come together with absolutely the same objective.”

I’m Bryan Lynn.

Words in This Story

cylinder – n. a circular object

lock – n. device used to close a door that requires a key to open

unit – n. measure used to express an amount or quantity

constant – adj. happening a lot or all the time

vault – n. a special room where valuable objects are kept

innovation – n. new idea or method that is being tried for the first time, or the use of such ideas or methods

formula – n. a set of letters, numbers, or symbols used to express a mathematical or scientific rule

accuracy – n. how correct or exact something is

application – n. the way in which something can be used for a particular purpose

scalable – adj. able to grow or be made larger

absolutely – adj. completely, without question

1 cylinder   

n.圆筒，柱(面)，汽缸

参考例句：

• What's the volume of this cylinder?这个圆筒的体积有多少？
• The cylinder is getting too much gas and not enough air.汽缸里汽油太多而空气不足。

2 platinum   

n.白金

参考例句：

• I'll give her a platinum ring.我打算送给她一枚白金戒指。
• Platinum exceeds gold in value.白金的价值高于黄金。

3 specially   

adv.特定地；特殊地；明确地

参考例句：

• They are specially packaged so that they stack easily.它们经过特别包装以便于堆放。
• The machine was designed specially for demolishing old buildings.这种机器是专为拆毁旧楼房而设计的。

4 decided   

adj.决定了的，坚决的；明显的，明确的

参考例句：

• This gave them a decided advantage over their opponents.这使他们比对手具有明显的优势。
• There is a decided difference between British and Chinese way of greeting.英国人和中国人打招呼的方式有很明显的区别。

5 fully   

adv.完全地，全部地，彻底地；充分地

参考例句：

• The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气，然后全部呼出。
• They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。

6 affected   

adj.不自然的，假装的

参考例句：

• She showed an affected interest in our subject.她假装对我们的课题感到兴趣。
• His manners are affected.他的态度不自然。

7 pollutants   

污染物质（尤指工业废物）( pollutant的名词复数 )

参考例句：

• Pollutants are constantly being released into the atmosphere. 污染物质正在不断地被排放到大气中去。
• The 1987 Amendments limit 301(g) discharges to a few well-studied nonconventional pollutants. 1987年的修正案把第301条（g）的普通排放限制施加在一些认真研究过的几种非常规污染物上。 来自英汉非文学 - 环境法 - 环境法

8 vault   

n.拱形圆顶，地窖，地下室

参考例句：

• The vault of this cathedral is very high.这座天主教堂的拱顶非常高。
• The old patrician was buried in the family vault.这位老贵族埋在家族的墓地里。

9 smoothly   

adv.平滑地，顺利地，流利地，流畅地

参考例句：

• The workmen are very cooperative,so the work goes on smoothly.工人们十分合作，所以工作进展顺利。
• Just change one or two words and the sentence will read smoothly.这句话只要动一两个字就顺了。