Constant physics

In Science, a constant physics is a quantity Physique whose numerical value is fixed. Contrary to a Constant mathematics, it implies a physically measurable size directly.

The values listed below are values which one noticed that they seemed constant and independent of all parameters used, and that the theory thus supposes really constant.

The constants without dimension , like the constant of fine structure , do not depend on the system on weights and measures used. The others would have obviously different values in different systems. Systems were proposed on the basis of fixing with 1 of the greatest possible number of constants, but were not great success for the moment.

List

Universal constants

Electromagnetism

Gravitation

Physicochemical constants

Atomic and nuclear constants

The number between brackets represents uncertainty on the last figures. For example: 6,673 (10) ×10^-11 mean 6,673×10^-11 ± 0,010×10^-11

Units of Planck

Exact values

With an aim of returning the calibration of the amp, basic unit of the international System (SI), more precise, the 18th General conference of the weights and measures (CGPM), adopted, in 1988, of the “exact” values of the constants of von Klitzing and Josephson:

R_K = h/e ² ≡ 2,5812807×10⁴ Ω (CIPM (1988) Recommendation 2, statement 56; 20)

K_J = 2e/h ≡ 4,835979×10¹⁴ Hz/V (CIPM (1988) Recommendation 1, statement 56; 19)

However, the Advisory committee of electricity (the CEC) stipulated that “Recommendations 1 (CI-1988) and 2 (CI-1988) do not constitute a redefinition of the units IF. The values of K_J and R_K, allowed by convention, cannot be used for the definition of the volt and the ohm, i.e. units of electromotive force and electrical resistance of the international System of units. If not the constant µ₀ would not have any more one exactly defined value, which would make null and void the definition of the amp, and the electric units would be incompatible with the definition of the kilogram and the units which derive from it. ”

Notwithstanding this, it is possible to redefine the kilogram, up to now the only basic unit of IF which is still defined by a physical standard (and is thus the only “degree of freedom” remaining in the system), starting from the exact values of the constants of von Klitzing and Josephson. If that is admitted, a whole series of constant physics acquire exact values consequently.

The definition of the kilogram would be then:

“ The mass which would be accelerated with exactly 2×10^-7 m/s ² if it were subjected to the force per meter between two parallel drivers, rectilinear, infinite length, circular section negligible and placed at a distance from 1 meter one of the other in the vacuum, and with through which circulates a constant electric current of exactly 6.241.509 629.152.650 000 elementary charges a second. ”

One from of deduced whereas the amp is worth exactly 6.241.509 629.152.650 000 elementary charges a second. The value of the Constante of Planck also rises from these exact values, like that of the Constante of fine structure.

See too

CODATA ~ international System of units ~ Measuring units in physics ~ Constant Conversion of the units ~ fundamental ~ Table of the astrophysical constants

External bonds

International office of the weights and measures
Values recommended CODATA 2002
CODATA (Committee one Dated for Science and Technology)
ICSU (International Council for Science)
to also see: Rev MOD Phy (flight 77, jan 2005): discuss the founded good of the values recommended, by the authors of the report/ratio (of which Barry NR Taylor, itself!)

Simple: Physical constant Zh-min-nan: Bu̍t-lí tiāⁿ-sò͘

Random links:

Veal escalopes Parmesan-almonds | PPM | The Carpenters | Edith Merry | François Aubrun