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New Kilogram definition
New Kilogram definition
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Old 20th May 2019, 03:51 PM   #11
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
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I was reading the difference is 1e-9 and that it will affect Ampere, Kelvin and many other definitions.
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Old 20th May 2019, 04:28 PM   #12
korpberget is offline korpberget  Norway
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Old 20th May 2019, 05:02 PM   #13
mondogenerator is offline mondogenerator  England
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Isn't the metre also due a new definition?

I guess these things, even when made from dimensionally stable materials, aren't as constant as they may need to be for centuries to come.

What intrigues me slightly is how scientists can be sure there relative measures and the equipment that measures them is orders of magnitude more precise.

Its like calibration. How do you accurately make a master standard (or a grand master standard?)

The few experiences I've had of calibration of instruments, the master standard for the standard was in many cases, a century old. It's still used, because it was just so accurate, there is nothing that can replace it.

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Old 20th May 2019, 05:17 PM   #14
Galu is offline Galu  Scotland
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Old 20th May 2019, 05:54 PM   #15
Galu is offline Galu  Scotland
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Vive la différence!

Since the International Prototype of the kilogram was introduced in 1889, measurements have shown that masses of the various National Prototypes are diverging.

The last comparisons showed that the spread had grown to 50 μg – about the same mass as a fly’s wing.

Although this may seem very little to the layperson, it's a huge amount for science. In the field of medicine, for example, 50 μg is a daily dose of vitamin D for a newborn baby.

Unit of the month – the kilogram - NPL
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Old 20th May 2019, 07:25 PM   #16
Dave R is offline Dave R  United States
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I guess in the future, we'll have to rely on someone from the scientific community to create a calibration sample. What would it be made from? Platinum-iridium alloy perhaps?
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Old 20th May 2019, 08:21 PM   #17
Galu is offline Galu  Scotland
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The National Prototype kilograms gradually put on 'weight' due to carbon-based and mercury contamination. Although the cylinders were stored in filtered laboratory air, small quantities of car exhaust fumes and mercury vapour from broken laboratory thermometers remained present.

To clean them, the cylinders were rubbed with chamois leather dipped in alcohol. But because every country cleans their kilograms differently and at different times, each prototype kilogram in the world is off by a different amount.

There can be little doubt that the new definition of the kilogram is absolutely essential to ensure a consistent and standard way of measuring mass with high precision.

The Kilogram Has Gained Weight
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Old 20th May 2019, 08:37 PM   #18
jo-briggs is offline jo-briggs  United Kingdom
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Quote:
Originally Posted by Galu View Post
Since the new definition relates the kilogram to the equivalent mass of the energy of a photon, there is a chance that the kilogram is now a little light!
I'll get your coat...
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Old 20th May 2019, 09:14 PM   #19
Galu is offline Galu  Scotland
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Originally Posted by jo-briggs View Post
I'll get your coat...
At least you got the joke! My puns don't always translate well - at home or abroad!
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Old 21st May 2019, 07:05 AM   #20
KaffiMann is online now KaffiMann  Norway
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New Kilogram definition
Quote:
Originally Posted by DF96 View Post
One really bad thing about these changes is that the permeability of vacuum is no longer exactly 4 pi 10^(-7). Exam questions which were exact will now only be approximate.
And not only exam answers, but the various Sciences would be better off if they resorted to several sets of algorithms for condition variables. Since you cannot guarantee to an infinitesimal that the value of a specific point in space (or vacuum container) is the same right now as it was a couple minutes ago. It would depend on a huge amount of data from monitoring sensors not practically applicable in each and every scenario. Vacuum is not Vacuum, the same as: a Watt is not a Watt.
Using a combination of algorithms would allow you to input a lot of different governing values for a large variation in conditions for each and every simulated experiment, because: Since the most common practice now seems to be fixed values as basis for computing, it can be hard to know exactly under which conditions a given experiment is more likely to succeed or fail.
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