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Kilogram to lose MASS appeal

The universal standard is about to change.

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Speedy Builder528/07/2017 14:21:21
1985 forum posts
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The block of metal that is the international standard by which mass is defined has been carefully stored in Paris for more than a century. But that could be about to change

The end of a scientific era is nigh, after experts discovered an accurate universal way to measure weight that means they can do away with 'Le Grand K' - the official standard by which all other metric weights are measured.

The Grand K is a cylinder made of a platinum-iridium alloy that is stored in three locked bell jars in environmentally monitored safe, which itself is kept in a vault in the International Bureau of Weights and Measures Pavillon de Breteuil, Saint-Cloud in the western suburbs of Paris.

It was manufactured in 1879. A decade later, it became the official global standard weight of one kilogramme.

The weight has been removed from storage only four times since it was created so that official replicas can be measured against it. The problem is, despite all efforts to keep the weight constant, tests prove that it is not the same mass as it was in 1889, and it is different to its replicas.

The differences are not enough to worry consumers in their everyday lives, but they can affect scientific calculations.

The Grand K is the last of the official units of measurement to rely on a physical standard, rather than a system of calculation that can be replicated anywhere.

Scientists now believe they can work out the mass using a calculation taking in Einstein's theory of relativity and Planck's constant - a vital component in the field of quantum mechanics.

The maths has been understood for some time, but experts now believe they have calculated Planck's constant accurately enough to improve on the weight standard set in 1889.

If these calculations, which were submitted by multiple teams earlier this month, are approved, the Grand K could be relegated to history by 2020, where it will join the metre bar - also made of the platinum-iridium alloy - which from 1791 until 1960 was the physical official definition of the length of a metre.

That measure is now defined as the distance travelled by a particle of light in 1/299,792,458 of a second.

Howard Lewis28/07/2017 15:00:27
3148 forum posts
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Ah well, Nothing lasts for ever!

But being a fully paid up Luddite, the Kilogramme never did have mass appeal to me.

Howard

Watford28/07/2017 16:24:07
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Posted by Speedy Builder5 on 28/07/2017 14:21:21:

... the metre bar - also made of the platinum-iridium alloy - which from 1791 until 1960 was the physical official definition of the length of a metre.

How did they do that in 1791? Is there any literature on this - would be interesting.

Mike

Richard S228/07/2017 16:43:08
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177 forum posts
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Posted by Speedy Builder5 on 28/07/2017 14:21:21:

If these calculations, which were submitted by multiple teams earlier this month, are approved, the Grand K could be relegated to history by 2020, where it will join the metre bar - also made of the platinum-iridium alloy - which from 1791 until 1960 was the physical official definition of the length of a metre.

They must have made it from what they believe to be Platinum originally (1791), as Iridium wasn't discovered until about 1803 I believe,.... by an Englishman?.

Also being of Luddite tendency, It won't bother me in the slightest either really.

 

Edited By Richard S2 on 28/07/2017 16:44:07

larry Phelan28/07/2017 18:11:57
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544 forum posts
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Never let the truth stand in the way of a good story !

not done it yet28/07/2017 18:42:25
4503 forum posts
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SB5 started correctly, refering to it as a mass, but sadly regressed to calling it a 'weight' further into his post. Weight is mg where m is the mass (which should not change) and g refers to the gravitational field which most certainly changes, dependent on location and a few other small but important factors (of which us mere mortals need not bother about).

Neil Wyatt28/07/2017 18:57:37
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Posted by Watford on 28/07/2017 16:24:07:
Posted by Speedy Builder5 on 28/07/2017 14:21:21:

... the metre bar - also made of the platinum-iridium alloy - which from 1791 until 1960 was the physical official definition of the length of a metre.

How did they do that in 1791? Is there any literature on this - would be interesting.

Mike

Making it wasn't hard, it's the measuring bit that's the challenge

duncan webster28/07/2017 19:31:06
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2543 forum posts
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Posted by Neil Wyatt on 28/07/2017 18:57:37:
Posted by Watford on 28/07/2017 16:24:07:
Posted by Speedy Builder5 on 28/07/2017 14:21:21:

... the metre bar - also made of the platinum-iridium alloy - which from 1791 until 1960 was the physical official definition of the length of a metre.

 

 

How did they do that in 1791? Is there any literature on this - would be interesting.

 

Mike

Making it wasn't hard, it's the measuring bit that's the challenge

The first one is easy, being French they made it and said 'that is exactly one metre because we say so'. Making exact copies is the difficult bit.

Edited By duncan webster on 28/07/2017 19:31:19

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