scholarly journals The fundamental constants of physics and the International System of Units

2021 ◽  
Author(s):  
Diederik Sybolt Wiersma ◽  
Giovanni Mana
Keyword(s):  
New York ◽  
International System ◽  
New York Times ◽  
Fundamental Constants ◽  
Decimal System ◽  
The Earth ◽  
System Of Units ◽  
Unit Of Measurement ◽  
Passenger Aircraft ◽  
Base Units

AbstractAir Canada managed to have a passenger aircraft run out of fuel in mid-air due to confusion about metric units (Stephenson in Mars climate orbiter mishap investigation board phase I report, NASA, 1999), and NASA lost an entire spacecraft due to a misunderstanding amongst engineers about the units used in the propulsion system design (Witkin in Jet’s fuel ran out after metric conversion errors, The New York Times, 1983). Measurements only make sense if the units are correct and well-defined. A unit of measurement is a definite magnitude of a quantity, defined by convention or law. Any other quantity of that kind can then be expressed as a multiple or submultiple of the unit of measurement. The Egyptians used the Farao as definite magnitude, while many years later, the french revolutionists introduced the earth as a reference and laid the foundations for the modern decimal system. Since recently, we have a truly universal and stable system that uses physics’s natural constants and laws to define the base units of measurement. This paper explains how this new concept works and how it is implemented in practice.

scholarly journals The kelvin redefinition and its mise en pratique

2016 ◽  
Vol 374 (2064) ◽  
pp. 20150037 ◽  
Author(s):  
B. Fellmuth ◽  
J. Fischer ◽  
G. Machin ◽  
S. Picard ◽  
P. P. M. Steur ◽  
...  
Keyword(s):  
International System ◽  
Thermodynamic Temperature ◽  
Fundamental Constants ◽  
Primary Thermometry ◽  
A Value ◽  
System Of Units ◽  
Mise En Pratique ◽  
Explicit Constant ◽  
Definition Of ◽  
Base Units

In 2018, it is expected that there will be a major revision of the International System of Units (SI) which will result in all of the seven base units being defined by fixing the values of certain atomic or fundamental constants. As part of this revision, the kelvin, unit of thermodynamic temperature, will be redefined by assigning a value to the Boltzmann constant k . This explicit-constant definition will define the kelvin in terms of the SI derived unit of energy, the joule. It is sufficiently wide to encompass any form of thermometry. The planned redefinition has motivated the creation of an extended mise en pratique (‘practical realization’) of the definition of the kelvin ( MeP -K), which describes how the new definition can be put into practice. The MeP -K incorporates both of the defined International Temperature Scales (ITS-90 and PLTS-2000) in current use and approved primary-thermometry methods for determining thermodynamic temperature values. The MeP -K is a guide that provides or makes reference to the information needed to perform measurements of temperature in accord with the SI at the highest level. In this article, the background and the content of the extended second version of the MeP -K are presented.

scholarly journals Quantity Calculus, Fundamental Constants, and SI Units

2018 ◽  
Vol 123 ◽  
Author(s):  
Barry N. Taylor
Keyword(s):  
International System ◽  
Fundamental Constants ◽  
Weights And Measures ◽  
International System Of Units ◽  
Si Units ◽  
System Of Units ◽  
Revised Si ◽  
Base Units ◽  
New Si

A revised International System of Units (SI) is expected to be established by the 26th General Conference on Weights and Measures when it convenes in November 2018 and to be put into practice starting on 20 May 2019, World Metrology Day. In consequence, the article published in this journal in 2011, “The Current SI Seen from the Perspective of the Proposed New SI,” is updated in this paper, which provides an opportunity to again demonstrate the usefulness of the quantity calculus in dealing with quantities and units. The quantity calculus and the seven defining constants of the current and revised SI are reviewed, and expressions for the seven current and revised SI base units are given. Relationships between the magnitudes of revised and current SI units and expressions for the numerical values of current SI defining constants expressed in revised SI units are also obtained using the quantity calculus.

scholarly journals SI-2019 and prospects for improving the accuracy of electrical measurements

2021 ◽  
pp. 35-39
Author(s):  
Iurii Pavlenko ◽  
Alexander Kolbasin ◽  
Olena Vаsileva
Keyword(s):  
International System ◽  
Fundamental Constants ◽  
Electrical Measurements ◽  
International System Of Units ◽  
Si Units ◽  
Accuracy Of Measurements ◽  
System Of Units ◽  
Measurement Units ◽  
Physical Laws ◽  
Base Units

Increasing requirements for the accuracy of measurements have led to the need to revise the existing International System of Units (SI). The important element of the SI-2019 reform is “the establishment of the SI base units through seven defining constants, the numerical values of which are fixed”. The approach to the establishment of the measurement units has fundamentally changed. If earlier a definition was given of how the unit is realized, now only the exact numerical values of the fundamental constants are fixed, and their values are expressed in the corresponding SI units. Measurement units are determined on the basis of known physical laws, which include certain fundamental constants. The article analyzes the changes in SI-2019 related to electrical measurements, and also discusses the prospects for the development of accurate electrical measurements.

scholarly journals On the five base quantities of nature and SI (The International System of Units)

2011 ◽  
Vol 47 (2) ◽  
pp. 241-246
Author(s):  
G. Kaptay
Keyword(s):  
International System ◽  
Fundamental Constant ◽  
Fundamental Constants ◽  
Planck Constant ◽  
Amount Of Substance ◽  
Substance Mole ◽  
System Of Units ◽  
Elementary Charge ◽  
Base Units ◽  
Constants Of Nature

It is shown here that five base quantities (and the corresponding five base units) of nature are sufficient to define all derived quantities (and their units) and to describe all natural phenomena. The base quantities (and their base units) are: length (m), mass (kg), time (s), temperature (K) and electric charge (C). The amount of substance (mole) is not taken as a base quantity of nature and the Avogadro constant is not considered as a fundamental constant of nature, as they are both based on an arbitrary definition (due to the arbitrary value of 0.012 kg for the mass of 1 mole of C-12 isotope). Therefore, the amount of substance (mole) is moved from the list of base quantities to the category of the supplementary units (to be re-created after its abrogation in 1995). Based on its definition, the luminous intensity (cd) is not a base quantity (unit), therefore it is moved to the list of derived quantities (units). The ampere and coulomb are exchanged by places in the list of base and derived units, as ampere is a speed of coulombs (but SI defines meter, not its speed as a base unit). The five base quantities are re-defined in this paper by connecting them to five fundamental constants of nature (the most accurately known frequency of the hydrogen atom, the speed of light, the Planck constant, the Boltzmann constant and the elementary charge) with their numerical values fixed in accordance with their CODATA 2006 values (to be improved by further experiments).

Quantum Metrology of Electrical Quantities and Mass

2021 ◽  
Vol 30 (3) ◽  
pp. 17-25
Author(s):  
Mun-Seog KIM ◽  
Dong-Hun CHAE ◽  
Kwang-Cheol LEE
Keyword(s):  
Quantum Physics ◽  
Josephson Effect ◽  
International System ◽  
Quantum Hall ◽  
Fundamental Constants ◽  
Planck Constant ◽  
System Of Units ◽  
Elementary Charge ◽  
Base Units ◽  
New Si

The new International System of Units (SI) became effective on 20 May 2019. In the new SI, the complete system of units can be traced to seven fixed values of the fundamental constants, not to seven base units as in the old system. Electrical metrology has two important quantum mechanical foundations. Here, we introduce the basics and the metrological applications of the Josephson effect and the quantum Hall effect, which play key roles in linking electrical quantities to the fundamental constants, including the Planck constant h, the elementary charge e, and the transition frequency of cesium 133 ΔνCs. Finally, we discuss the redefinition of the kilogram as one of the important examples of electrical metrology based on quantum physics.

scholarly journals Adapting the International System of Units to the twenty-first century

2011 ◽  
Vol 369 (1953) ◽  
pp. 3907-3924 ◽  
Author(s):  
Ian M. Mills ◽  
Peter J. Mohr ◽  
Terry J. Quinn ◽  
Barry N. Taylor ◽  
Edwin R. Williams
Keyword(s):  
International System ◽  
International Committee ◽  
First Century ◽  
Weights And Measures ◽  
International System Of Units ◽  
System Of Units ◽  
Elementary Charge ◽  
Magnetic Constant ◽  
Base Units ◽  
New Si

We review the proposal of the International Committee for Weights and Measures (Comité International des Poids et Mesures, CIPM), currently being considered by the General Conference on Weights and Measures (Conférences Générales des Poids et Mesures, CGPM), to revise the International System of Units (Le Système International d'Unitès, SI). The proposal includes new definitions for four of the seven base units of the SI, and a new form of words to present the definitions of all the units. The objective of the proposed changes is to adopt definitions referenced to constants of nature, taken in the widest sense, so that the definitions may be based on what are believed to be true invariants. In particular, whereas in the current SI the kilogram, ampere, kelvin and mole are linked to exact numerical values of the mass of the international prototype of the kilogram, the magnetic constant (permeability of vacuum), the triple-point temperature of water and the molar mass of carbon-12, respectively, in the new SI these units are linked to exact numerical values of the Planck constant, the elementary charge, the Boltzmann constant and the Avogadro constant, respectively. The new wording used expresses the definitions in a simple and unambiguous manner without the need for the distinction between base and derived units. The importance of relations among the fundamental constants to the definitions, and the importance of establishing a mise en pratique for the realization of each definition, are also discussed.

scholarly journals Definition of the mole (IUPAC Recommendation 2017)

2018 ◽  
Vol 90 (1) ◽  
pp. 175-180 ◽  
Author(s):  
Roberto Marquardt ◽  
Juris Meija ◽  
Zoltán Mester ◽  
Marcy Towns ◽  
Ron Weir ◽  
...  
Keyword(s):  
International System ◽  
International Committee ◽  
Fundamental Physical Constants ◽  
Weights And Measures ◽  
Technical Report ◽  
System Of Units ◽  
Iupac Recommendation ◽  
Definition Of ◽  
Base Units ◽  
Fundamental Physical

AbstractIn 2011 the General Conference on Weights and Measures (CGPM) noted the intention of the International Committee for Weights and Measures (CIPM) to revise the entire International System of Units (SI) by linking all seven base units to seven fundamental physical constants. Of particular interest to chemists, new definitions for the kilogram and the mole have been proposed. A recent IUPAC Technical Report discussed these new definitions in relation to immediate consequences for the chemical community. This IUPAC Recommendation on the preferred definition of the mole follows from this Technical Report. It supports a definition of the mole based on a specified number of elementary entities, in contrast to the present 1971 definition.

RESEARCH ON STABILITY ANALYSIS OF INTERNATIONAL PROTOTYPE KILOGRAM

2013 ◽  
Vol 24 ◽  
pp. 1360004
Author(s):  
XIAOPING REN ◽  
YUE ZHANG ◽  
JIAN WANG ◽  
QINGXIONG REN ◽  
QINGMAO REN
Keyword(s):  
Stability Analysis ◽  
International System ◽  
Calibration Data ◽  
Surface Stability ◽  
Standard Methods ◽  
System Of Units ◽  
Modern Mass ◽  
Base Units ◽  
Adjustment Of Parameters ◽  
Measured Mass

Today, the kilogram is the last of the seven base units of the International System of Units (SI) which is based on a physical artifact. The demands of modern mass metrology have led to an increasing focus on the surface stability and analysis of mass standard. Methods for evaluating the correlation between the measured mass values of the prototypes of the kilogram includes: collection of historical calibration data for kilogram prototypes, setting up a model for deterministic and random changes in the mass of a kilogram prototype (relative to the IPK), adjustment of parameters in a model using historical calibration data, and prediction of future mass values of a kilogram prototype using model and adjusted parameters.

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