Tuesday , December 1 2020

Definition of kilograms to be changed



Copu of Master KilogramImage copyright
SPL

Image Caption

The masterpiece, sealed in a jar and stored in a safe in Paris, no longer weighs the same as this "exact" copy – as scientists say is "not scientifically acceptable"

Researchers are set to change how kilograms are defined.

Currently, it is defined by the importance of a platinum-based pier called "Le Grand K", which is locked in a safe in Paris.

Researchers are expected to vote to get rid of it to define a kilo for an electric current.

The decision is made at the General Conference on Weights and Actions in Paris.

However, some researchers like Purdey Williams at the National Physical Laboratory have mixed feelings about the change.

"I have not been involved in this project for a long time, but I feel strange at the kilogram," he said.

"I think it's so exciting and this is a really big moment. I'm a little sorry for the change. But it's an important step forward and the new system will work much better So it's also a really exciting time , and I can not wait for it to happen. "

Why kill the kilogram?

Le Grand K has been at the forefront of the international weight measurement system since 1889. There are also several close replicas.

But the days of the championship are numbered. Its weight has changed over the years because it has deteriorated. The kilogram, like the pope, is impossible, so other weights need to be adjusted accordingly.

In a world where accurate measurement is now critical in many areas, such as drug development, nanotechnology and precision engineering, they are responsible for maintaining the system plan to prevent Le Grand K's increasingly wrong rule.

How wrong is Le Grand K?

Fluctuation is about 50 parts in billion, less than the weight of a single eyelash. But even if it's small, the change can have important consequences. Coming in is an electrical measurement that Dr. Stuart Davidson, NPL's mass spectrometry manager, says is more stable, more accurate, and more even.

"We know from comparing the kilogram in Paris with all the copies of kilograms around the world that there are differences between them and Le Grand K himself," he said.

"This is not acceptable from a scientific point of view. So even if Le Grand K is fit for purpose at the moment, it will not be 100 years."

How does the new system work?

Electromagnets generate power. Screwdrivers use them on cranes to lift and move large metal objects, such as cars. The traction of the electromagnet, the force it exerts, is directly related to the amount of electrical current passing through its coils. There is therefore a direct relationship between electricity and weight.

So, in principle, researchers can define a kilo or other weight in terms of the amount of electricity needed to counteract their power.

Here is the tricky part

There is a quantity related to electric current, called Planck's constant – called after the German physicist Max Planck and denoted the symbol hrs.

But hrs is an incredibly small number, and to measure it, scientist Dr. Bryan Kibble built a super-corrected set of scales. The Kibble balance, as it has become known, has an electromagnet pulling down on one side of the scales and a weight – say a kilo – on the other hand.

The electric current passing through the electromagnet increases until the two sides are perfectly balanced.

By measuring the current flowing through the electromagnet to incredible precision, researchers could figure out hrs to an accuracy of 0.000001%.

This breakthrough has paved the way for Le Grand K to be deposited by Die Kleine hrs".

What are the benefits of the new system?

For a few decades, all of the world's replica kings must be checked against Le Grand K. The new system, assumed, will allow anyone with a Kibble balance to control their weights at any time and anywhere, according to NPL's Ian Robinson .

"It feels very good at this time. I think it's the right decision. Once we've done it, it will be stable in the foreseeable future," he said.

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