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**Physics, Astronomy & Cosmology / Re: Is mass a number?**

« **on:**02/05/2022 18:59:59 »

Hi all,

OK varsigma,

If I understand your request correctly regarding is mass a number rather than a physical thing.

Its based on empirically proven physical constants, to allow precise replication.

So the unit of mass is the Kg Kilogram in the system of international units, which was originally simply the mass of a litre of water, which is actually accurate to 30 parts per million.

However in 1799, it was replaced by an all-platinum kilogram prototype that was fabricated with the objective that it would equal, as close as was scientifically feasible for the day, the mass of one cubic decimetre of water at 4 °C. It was called the Kilogramme des Archives as it was stored in the Archives Nationales in Paris.

This remained the SI standard till 2019.

https://en.wikipedia.org/wiki/International_System_of_Units

The kilogram was the last of the SI units to be defined by a physical artifact, although precision kilogram masses remain in use as secondary standards for ordinary purposes.

https://en.wikipedia.org/wiki/Kilogram#Redefinition_based_on_fundamental_constants

The requirement to produce replicas caused the mass of these to vary by amounts approximately 50 micro grams.

Therefore,

The International Committee for Weights and Measures (CIPM) approved a redefinition of the SI base units in November 2018 that defines the kilogram by defining the Planck constant to be exactly 6.62607015×10−34 kg⋅m2⋅s−1, effectively defining the kilogram in terms of the SI base units "second" and the "metre".

Therefore, dimensions of energy times time, (mass × length^2 / time) together with other physical constants

This was done so that the standard can be independently reproduced in different laboratories by following a written specification, from empirically proven physical constants.

And the units were coherent to mass length and time.

https://en.wikipedia.org/wiki/Kilogram#Acceptance_of_the_Giorgi_system,_leading_to_the_MKSA_system_and_the_SI

It would appear the Kibble balance is the dominate apparatus in this regard.

https://en.wikipedia.org/wiki/Kibble_balance

which hopefully the design/engineering explains to you how mass is not just a number but a based on combination of physical constants allows a very accurate replication of fixed amount of Mass.

A conducting wire of length

weight = mg = BLI

https://en.wikipedia.org/wiki/Lorentz_force

OK varsigma,

If I understand your request correctly regarding is mass a number rather than a physical thing.

Its based on empirically proven physical constants, to allow precise replication.

So the unit of mass is the Kg Kilogram in the system of international units, which was originally simply the mass of a litre of water, which is actually accurate to 30 parts per million.

However in 1799, it was replaced by an all-platinum kilogram prototype that was fabricated with the objective that it would equal, as close as was scientifically feasible for the day, the mass of one cubic decimetre of water at 4 °C. It was called the Kilogramme des Archives as it was stored in the Archives Nationales in Paris.

This remained the SI standard till 2019.

https://en.wikipedia.org/wiki/International_System_of_Units

The kilogram was the last of the SI units to be defined by a physical artifact, although precision kilogram masses remain in use as secondary standards for ordinary purposes.

https://en.wikipedia.org/wiki/Kilogram#Redefinition_based_on_fundamental_constants

The requirement to produce replicas caused the mass of these to vary by amounts approximately 50 micro grams.

Therefore,

The International Committee for Weights and Measures (CIPM) approved a redefinition of the SI base units in November 2018 that defines the kilogram by defining the Planck constant to be exactly 6.62607015×10−34 kg⋅m2⋅s−1, effectively defining the kilogram in terms of the SI base units "second" and the "metre".

Therefore, dimensions of energy times time, (mass × length^2 / time) together with other physical constants

This was done so that the standard can be independently reproduced in different laboratories by following a written specification, from empirically proven physical constants.

And the units were coherent to mass length and time.

https://en.wikipedia.org/wiki/Kilogram#Acceptance_of_the_Giorgi_system,_leading_to_the_MKSA_system_and_the_SI

Quote

To summarize, the ultimate reason that the kilogram was chosen over the gram as the base unit of mass was, in one word, the volt-ampere. Namely, the combination of the meter and the kilogram was the only choice of base units of length and mass such that 1. the volt-ampere—which is also called the watt and which is the unit of power in the practical system of electrical units—is coherent, 2. the base units of length and mass are decimal multiples or submultiples of the meter and the gram, and 3. the base units of length and mass have convenient sizes.

It would appear the Kibble balance is the dominate apparatus in this regard.

https://en.wikipedia.org/wiki/Kibble_balance

which hopefully the design/engineering explains to you how mass is not just a number but a based on combination of physical constants allows a very accurate replication of fixed amount of Mass.

A conducting wire of length

**L**that carries an electric current**I**perpendicular to a magnetic field of strength**B**experiences a Lorentz force equal to the product of these variables. In the Kibble balance, the current is varied so that this force counteracts the weight w of a mass m to be measured. This principle is derived from the ampere balance.**w**is given by the mass**m**multiplied by the local gravitational acceleration**g**weight = mg = BLI

https://en.wikipedia.org/wiki/Lorentz_force