Related papers: A Better Definition of the Kilogram
With the redefinition of the international system of units, the value of the Planck constant was fixed, similarly to the values of the unperturbed ground state hyperfine transition frequency of the $^{133}$Cs atom, speed of light in vacuum.…
The Avogadro constant links the atomic and the macroscopic properties of matter. Since the molar Planck constant is well known via the measurement of the Rydberg constant, it is also closely related to the Planck constant. In addition, its…
An exact value for Avodagro's number, namely NA* = (84446888)^3, is proposed. The number 84446888 represents the side length of a cube of atoms whose volume is closest, among all integral side lengths, to the current official NIST value of…
This article reviews several recent proposed redefinitions of the kilogram, and compares them with respect to practical realizations, uncertainties (estimated standard deviations), and educational aspects.
The new International System of Units may let us select an integer value for Avogadro's number. Some might prefer an integer that's divisible by 12, so that an integer number of $^{12}C$ atoms may be associated (to first order) with a…
We consider a recent proposal [1] to redefine the kilogram in terms of natural constants. In our opinion, the main objective of the redefinition should be to build such a version of the SI system in which the electric measurements are…
We discuss the role of fundamental constants and measurement data for the Planck, Avogadro and Boltzmann constants and the elementary electric charge in connection with the planned transition to new definitions of four base SI units (the…
New results are reported from an ongoing international research effort to accurately determine the Avogadro constant by counting the atoms in an isotopically enriched silicon crystal. The surfaces of two 28Si-enriched spheres were…
The electron mass in atomic mass units has been determined with a relative uncertainty of $2.8\cdot 10^{-11}$, which represents a 13-fold improvement of the 2010 CODATA value. The underlying measurement principle combines a high-precision…
We discuss different sets of defining constants, fixed values of which are considered in connection with the transition to new definitions of four SI units (the kilogram, the mole, the ampere, and the kelvin). The notion of constant's order…
Measuring the effect of gravity on antimatter is a longstanding problem in physics that has significant implications for our understanding of the fundamental nature of the universe. Here, we present a technique to measure the gravitational…
Advantages and disadvantages of fixation of fundamental physical constants' values for definition of SI units are considered. The case with a new definition of the mass unit on the base of a fixed value of the Avogadro constant is studied…
The revised International System of Units (SI), expected to be approved late in 2018, has implications for physics pedagogy; the ampere definition which dates from 1948 will be replaced by a definition that fixes the numerical value of the…
The quest for the value of the electron's atomic mass has been subject of continuing efforts over the last decades. Among the seemingly fundamental constants which parameterize the Standard Model (SM) of physics and which are thus…
A global effort to redefine our International System of Units (SI) is underway and the change to the new system is expected to occur in 2018. Within the newly redefined SI, the present base units will still exist but be derived from fixed…
Recent proposals to re-define some of the base units of the SI make use of definitions that refer to fixed numerical values of certain constants. We review these proposals in the context of the latest results of the least-squares adjustment…
The four SI base units are proposed to be redefined in two stages: first, the kilogram, mole and ampere should be defined, and then the kelvin. To realize the redefinition of a base unit of the SI in terms of fundamental physical constant…
To base the kilogram definition on the atomic mass of the silicon 28 atom, the present relative uncertainty of the silicon 28 lattice parameter must lowered to 3E-9. To achieve this goal, a new experimental apparatus capable of a centimetre…
We report on the precise measurement of the atomic mass of a single proton with a purpose-built Penning-trap system. With a precision of 32 parts-per-trillion our result not only improves on the current CODATA literature value by a factor…
A drawback of the new SI is that by fixing the value of the elementary charge $e$, the vacuum magnetic permeability $\mu_\circ$ and impedance $Z_\circ=\mu_\circ c$ are no longer fixed, but get written proportionately to $\alpha$. All…