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Physical Constants
This chapter describes macros for the values of physical constants, such as the speed of light, c, and gravitational constant, G. The
values are available in different unit systems, including the standard MKSA system (meters, kilograms, seconds, amperes) and the CGSM
system (centimeters, grams, seconds, gauss), which is commonly used in Astronomy.
##References and Further Reading
The authoritative sources for physical constants are the 2006 CODATA recommended values, published in the article below. Further
information on the values of physical constants is also available from the NIST website.
P.J. Mohr, B.N. Taylor, D.B. Newell, “CODATA Recommended Values of the Fundamental Physical Constants: 2006”, Reviews of Modern Physics,
80(2), pp. 633–730 (2008).
http://www.physics.nist.gov/cuu/Constants/index.html
http://physics.nist.gov/Pubs/SP811/appenB9.html
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The length of 1 angstrom. m
The length of 1 astronomical unit (mean earth-sun distance), au. m
The pressure of 1 bar. kg / m s^2
The Bohr Magneton, \mu_B. A m^2
The Boltzmann constant, k. kg m^2 / K s^2
The energy of 1 British Thermal Unit, btu. kg m^2 / s^2
The energy of 1 calorie. kg m^2 / s^2
The volume of 1 Canadian gallon. m^3
The activity of 1 curie. 1 / s
The number of seconds in 1 day. s
The electric dipole moment of 1 Debye, D. A s^2 / m^2
The force of 1 Dyne = 10^-5 Newton. kg m / s^2
The charge of the electron, e. A s
The absolute value of the magnetic moment of the electron, \mu_e. The physical magnetic moment
of the electron is negative. A m^2
The energy of 1 electron volt, eV. kg m^2 / s^2
The energy 1 erg = 10^-7 Joule. kg m^2 / s^2
The molar charge of 1 Faraday. A s / mol
The length of 1 fathom. m
The illuminance of 1 footcandle. cd sr / m^2
The luminance of 1 footlambert. cd sr / m^2
The magnetic field of 1 Gauss. kg / A s^2
The force of 1 gram weight. kg m / s^2
The gravitational constant, G. m^3 / kg s^2
The standard gravitational acceleration on Earth, g. m / s^2
The area of 1 hectare. m^2
The power of 1 horsepower. kg m^2 / s^3
The number of seconds in 1 hour. s
The pressure of 1 inch of mercury. kg / m s^2
The pressure of 1 inch of water. kg / m s^2
The SI unit of energy, 1 Joule. kg m^2 / s^2
The speed of 1 kilometer per hour. m / s
The force of 1 kilopound weight. kg m / s^2
The speed of 1 knot. m / s
The luminance of 1 lambert. cd sr / m^2
The distance of 1 light-year, ly. m
The volume of 1 liter. m^3
The luminous flux of 1 lumen. cd sr
The illuminance of 1 lux. cd sr / m^2
The mass of the electron, m_e. kg
The mass of the muon, m_\mu. kg
The mass of the neutron, m_n. kg
The mass of the proton, m_p. kg
The pressure of 1 meter of mercury. kg / m s^2
The mass of 1 metric ton (1000 kg). kg
The length of 1 micron. m
The length of 1 mil (1/1000th of an inch). m
The speed of 1 mile per hour. m / s
The number of seconds in 1 minute. s
The molar gas constant, R_0. kg m^2 / K mol s^2
The length of 1 nautical mile. m
The SI unit of force, 1 Newton. kg m / s^2
The Nuclear Magneton, \mu_N. A m^2
The distance of 1 parsec, pc. m
The illuminance of 1 phot. cd sr / m^2
The volume of 1 pint. m^3
Planck’s constant, h. kg m^2 / s
Planck’s constant divided by 2\pi, \hbar. kg m^2 / s
The length of 1 printer’s point (1/72 inch). m
The dynamic viscosity of 1 poise. kg m^-1 s^-1
The force of 1 poundal. kg m / s^2
The force of 1 pound weight. kg m / s^2
The magnetic moment of the proton, \mu_p. A m^2
The pressure of 1 pound per square inch. kg / m s^2
The volume of 1 quart. m^3
The absorbed dose of 1 rad. m^2 / s^2
The exposure of 1 roentgen. A s / kg
The Rydberg constant, Ry, in units of energy. This is related to the Rydberg inverse
wavelength R_\infty by Ry = h c R_\infty. kg m^2 / s^2
The speed of light in vacuum, c. m / s
The standard gas volume, V_0. m^3 / mol
The pressure of 1 standard atmosphere. kg / m s^2
The Stefan-Boltzmann radiation constant, \sigma. kg / K^4 s^3
The luminance of 1 stilb. cd / m^2
The kinematic viscosity of 1 stokes. m^2 / s
The length of 1 TeX point (1/72.27 inch). m
The energy of 1 Therm. kg m^2 / s^2
The Thomson cross section, \sigma_T. m^2
The pressure of 1 torr. kg / m s^2
The mass of 1 troy ounce. kg
The volume of 1 UK gallon. m^3
The unified atomic mass, amu. kg
The volume of 1 US gallon. m^3
The permeability of free space, \mu_0. This constant is defined in the MKSA system only.
kg m / A^2 s^2
The permittivity of free space, \epsilon_0. This constant is defined in the MKSA system only.
A^2 s^4 / kg m^3
The number of seconds in 1 week. s
Avogadro’s number, N_a. 1 / mol
The electromagnetic fine structure constant \alpha. 1