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Home / Science / Definition of the kilogram set to be changed

Definition of the kilogram set to be changed



  Copu of Master Kilogram

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SPL

Caption

The original kilogram sealed in a jar and kept in a safe in Paris no longer weighs like this "exact" one. Copy ̵
1; what researchers say is "not scientifically acceptable"

Scientists will change the definition of the kilogram.

Currently it is defined by the weight of a platinum-based bar called "Le Grand K", which is trapped in a safe in Paris.

Researchers are expected to choose to define one kilogram in terms of electrical current.

The decision is to be taken at the General Conference for Dimensions and Measures in Paris.

But some scientists, such as Purdey Williams of the National Physical Laboratory, have mixed feelings about change.

I've been on this project for too long, but I feel a strange bond to the kilogram, "he said.

" I think it's such an exciting thing and that's a really big moment. That's why I'm a bit sad about the change. But it's an important step forward and the new system will work much better. It's also a really exciting time. And I can not wait for it to happen.

Why kill the kilogram?

Le Grand K was at the forefront of the international system of measuring weights since 1889. There are also several replicas.

But the days of the kilogram are numbered The kilogram, like the Pope, is infallible so other weights need to be adjusted accordingly.

In a world where accurate measurements are now critical in many areas, such as drug development in nanotechnology and in precision mechanics, those responsible are responsible for the system plan to lift the increasingly flawed rule of Le Grand K.

How wrong is Le Grand K?

The turnover is about 50 parts of a billion, less than the weight of a single eyelash, even though it is tiny, the change can have important consequences: an electrical measurement that, according to Dr. St Davidson, head of mass spectrometry at NPL, is more stable, accurate, and more egalitarian.

"We know from a comparison of the kilogram in Paris with all the copies of the kilogram Around the world there are discrepancies between them and Le Grand K itself," he said.

"This is unacceptable from a scientific point of view, and although Le Grand K is currently fit for purpose, it will not be in 100 years."

How does the new system work?

Electromagnets generate a force. They use junkyard cranes to lift and move large metal objects like cars. The pull of the electromagnet, the force it exerts, is directly related to the amount of electrical current flowing through its coils. So there is a direct relationship between electricity and weight.

Scientists can thus, in principle, define one kilogram or other weight in terms of the amount of electricity required to counteract its force.

Here's the tricky part

There's one size that relates weight to electric current, called Planck's constant – named after the German physicist Max Planck and labeled with the symbol h ,

But h is an incredibly small number, and to measure that, the researcher Dr. Bryan Kibble a very accurate scale. The so-called Kibble scale has an electromagnet that pulls down on one side of the scale, on the other side a weight – about one kilogram -.

The electric current flowing through the electromagnet is increased until the two sides are perfectly balanced.

By measuring the current flowing through the electromagnet with incredible precision, researchers h were able to calculate a result accuracy of 0.000001%.

With this breakthrough, Le Grand K could be dropped from "Die Kleine h ".

What are the advantages of the new system?

Every In a few decades, all replica kilograms in the world must be matched against Le Grand K. When the new system is introduced, anyone with a kibble balance can control their weight anytime, anywhere, Dr. Ian Robinson of NPL.

"It feels really good to be at this point, I think it's the right decision, and once we've done that, it'll be stable for the foreseeable future," he said.

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