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 @cindex physical constants
 @cindex constants, physical
 @cindex conversion of units
 @cindex units, conversion of
 This chapter describes macros for the values of physical constants, such
 as the speed of light, @math{c}, and gravitational constant, @math{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.

 The definitions of constants in the MKSA system are available in the file
 @file{gsl_const_mksa.h}.  The constants in the CGSM system are defined in
 @file{gsl_const_cgsm.h}.  Dimensionless constants, such as the fine
 structure constant, which are pure numbers are defined in
 @file{gsl_const_num.h}.

 @menu
 * Fundamental Constants::
 * Astronomy and Astrophysics::
 * Atomic and Nuclear Physics::
 * Measurement of Time::
 * Imperial Units ::
 * Speed and Nautical Units::
 * Printers Units::
 * Volume Area and Length::
 * Mass and Weight ::
 * Thermal Energy and Power::
 * Pressure::
 * Viscosity::
 * Light and Illumination::
 * Radioactivity::
 * Force and Energy::
 * Prefixes::
 * Physical Constant Examples::
 * Physical Constant References and Further Reading::
 @end menu

 The full list of constants is described briefly below.  Consult the
 header files themselves for the values of the constants used in the
 library.

 @node Fundamental Constants
 @section Fundamental Constants
 @cindex fundamental constants
 @cindex constants, fundamental
 @table @code
 @item GSL_CONST_MKSA_SPEED_OF_LIGHT
 The speed of light in vacuum, @math{c}.

 @item GSL_CONST_MKSA_VACUUM_PERMEABILITY
 The permeability of free space, @math{\mu_0}. This constant is defined
 in the MKSA system only.

 @item GSL_CONST_MKSA_VACUUM_PERMITTIVITY
 The permittivity of free space, @math{\epsilon_0}.  This constant is
 defined in the MKSA system only.

 @item GSL_CONST_MKSA_PLANCKS_CONSTANT_H
 Planck's constant, @math{h}.

 @item GSL_CONST_MKSA_PLANCKS_CONSTANT_HBAR
 Planck's constant divided by @math{2\pi}, @math{\hbar}.

 @item GSL_CONST_NUM_AVOGADRO
 Avogadro's number, @math{N_a}.

 @item GSL_CONST_MKSA_FARADAY
 The molar charge of 1 Faraday.

 @item GSL_CONST_MKSA_BOLTZMANN
 The Boltzmann constant, @math{k}.

 @item GSL_CONST_MKSA_MOLAR_GAS
 The molar gas constant, @math{R_0}.

 @item GSL_CONST_MKSA_STANDARD_GAS_VOLUME
 The standard gas volume, @math{V_0}.

 @item GSL_CONST_MKSA_STEFAN_BOLTZMANN_CONSTANT
 The Stefan-Boltzmann radiation constant, @math{\sigma}.

 @item GSL_CONST_MKSA_GAUSS
 The magnetic field of 1 Gauss.
 @end table

 @node Astronomy and Astrophysics
 @section Astronomy and Astrophysics
 @cindex astronomical constants
 @table @code
 @item GSL_CONST_MKSA_ASTRONOMICAL_UNIT
 The length of 1 astronomical unit (mean earth-sun distance), @math{au}.

 @item GSL_CONST_MKSA_GRAVITATIONAL_CONSTANT
 The gravitational constant, @math{G}.

 @item GSL_CONST_MKSA_LIGHT_YEAR
 The distance of 1 light-year, @math{ly}.

 @item GSL_CONST_MKSA_PARSEC
 The distance of 1 parsec, @math{pc}.

 @item GSL_CONST_MKSA_GRAV_ACCEL
 The standard gravitational acceleration on Earth, @math{g}.

 @item GSL_CONST_MKSA_SOLAR_MASS
 The mass of the Sun.
 @end table

 @node Atomic and Nuclear Physics
 @section Atomic and Nuclear Physics
 @cindex atomic physics, constants
 @cindex nuclear physics, constants
 @table @code
 @item GSL_CONST_MKSA_ELECTRON_CHARGE
 The charge of the electron, @math{e}.

 @item GSL_CONST_MKSA_ELECTRON_VOLT
 The energy of 1 electron volt, @math{eV}.

 @item GSL_CONST_MKSA_UNIFIED_ATOMIC_MASS
 The unified atomic mass, @math{amu}.

 @item GSL_CONST_MKSA_MASS_ELECTRON
 The mass of the electron, @math{m_e}.

 @item GSL_CONST_MKSA_MASS_MUON
 The mass of the muon, @math{m_\mu}.

 @item GSL_CONST_MKSA_MASS_PROTON
 The mass of the proton, @math{m_p}.

 @item GSL_CONST_MKSA_MASS_NEUTRON
 The mass of the neutron, @math{m_n}.

 @item GSL_CONST_NUM_FINE_STRUCTURE
 The electromagnetic fine structure constant @math{\alpha}.

 @item GSL_CONST_MKSA_RYDBERG
 The Rydberg constant, @math{Ry}, in units of energy.  This is related to
 the Rydberg inverse wavelength @math{R} by @math{Ry = h c R}.

 @item GSL_CONST_MKSA_BOHR_RADIUS
 The Bohr radius, @math{a_0}.

 @item GSL_CONST_MKSA_ANGSTROM
 The length of 1 angstrom.

 @item GSL_CONST_MKSA_BARN
 The area of 1 barn.

 @item GSL_CONST_MKSA_BOHR_MAGNETON
 The Bohr Magneton, @math{\mu_B}.

 @item GSL_CONST_MKSA_NUCLEAR_MAGNETON
 The Nuclear Magneton, @math{\mu_N}.

 @item GSL_CONST_MKSA_ELECTRON_MAGNETIC_MOMENT
 The absolute value of the magnetic moment of the electron, @math{\mu_e}.
 The physical magnetic moment of the electron is negative.

 @item GSL_CONST_MKSA_PROTON_MAGNETIC_MOMENT
 The magnetic moment of the proton, @math{\mu_p}.

 @item GSL_CONST_MKSA_THOMSON_CROSS_SECTION
 The Thomson cross section, @math{\sigma_T}.

 @item GSL_CONST_MKSA_DEBYE
 The electric dipole moment of 1 Debye, @math{D}.
 @end table


 @node Measurement of Time
 @section Measurement of Time
 @cindex time units
 @table @code
 @item GSL_CONST_MKSA_MINUTE
 The number of seconds in 1 minute.

 @item GSL_CONST_MKSA_HOUR
 The number of seconds in 1 hour.

 @item GSL_CONST_MKSA_DAY
 The number of seconds in 1 day.

 @item GSL_CONST_MKSA_WEEK
 The number of seconds in 1 week.
 @end table


 @node Imperial Units
 @section Imperial Units
 @cindex imperial units
 @cindex units, imperial
 @table @code
 @item GSL_CONST_MKSA_INCH
 The length of 1 inch.

 @item GSL_CONST_MKSA_FOOT
 The length of 1 foot.

 @item GSL_CONST_MKSA_YARD
 The length of 1 yard.

 @item GSL_CONST_MKSA_MILE
 The length of 1 mile.

 @item GSL_CONST_MKSA_MIL
 The length of 1 mil (1/1000th of an inch).
 @end table


 @node Speed and Nautical Units
 @section Speed and Nautical Units
 @cindex nautical units

 @table @code
 @item GSL_CONST_MKSA_KILOMETERS_PER_HOUR
 The speed of 1 kilometer per hour.

 @item GSL_CONST_MKSA_MILES_PER_HOUR
 The speed of 1 mile per hour.

 @item GSL_CONST_MKSA_NAUTICAL_MILE
 The length of 1 nautical mile.

 @item GSL_CONST_MKSA_FATHOM
 The length of 1 fathom.

 @item GSL_CONST_MKSA_KNOT
 The speed of 1 knot.
 @end table


 @node Printers Units
 @section Printers Units
 @cindex printers units

 @table @code
 @item GSL_CONST_MKSA_POINT
 The length of 1 printer's point (1/72 inch).

 @item GSL_CONST_MKSA_TEXPOINT
 The length of 1 TeX point (1/72.27 inch).
 @end table


 @node Volume Area and Length
 @section Volume, Area and Length
 @cindex volume units

 @table @code
 @item GSL_CONST_MKSA_MICRON
 The length of 1 micron.

 @item GSL_CONST_MKSA_HECTARE
 The area of 1 hectare.

 @item GSL_CONST_MKSA_ACRE
 The area of 1 acre.

 @item GSL_CONST_MKSA_LITER
 The volume of 1 liter.

 @item GSL_CONST_MKSA_US_GALLON
 The volume of 1 US gallon.

 @item GSL_CONST_MKSA_CANADIAN_GALLON
 The volume of 1 Canadian gallon.

 @item GSL_CONST_MKSA_UK_GALLON
 The volume of 1 UK gallon.

 @item GSL_CONST_MKSA_QUART
 The volume of 1 quart.

 @item GSL_CONST_MKSA_PINT
 The volume of 1 pint.
 @end table


 @comment @node Cookery
 @comment @section Cookery
 @comment @commentindex cookery units

 @comment @table @commentode
 @comment @item GSL_CONST_MKSA_CUP
 @comment The volume of 1 cup.

 @comment @item GSL_CONST_MKSA_FLUID_OUNCE
 @comment The volume of 1 fluid ounce.

 @comment @item GSL_CONST_MKSA_TABLESPOON
 @comment The volume of 1 tablespoon.

 @comment @item GSL_CONST_MKSA_TEASPOON
 @comment The volume of 1 teaspoon.
 @comment @end table


 @node Mass and Weight
 @section Mass and Weight
 @cindex mass, units of
 @cindex weight, units of
 @table @code
 @item GSL_CONST_MKSA_POUND_MASS
 The mass of 1 pound.

 @item GSL_CONST_MKSA_OUNCE_MASS
 The mass of 1 ounce.

 @item GSL_CONST_MKSA_TON
 The mass of 1 ton.

 @item GSL_CONST_MKSA_METRIC_TON
 The mass of 1 metric ton (1000 kg).

 @item GSL_CONST_MKSA_UK_TON
 The mass of 1 UK ton.

 @item GSL_CONST_MKSA_TROY_OUNCE
 The mass of 1 troy ounce.

 @item GSL_CONST_MKSA_CARAT
 The mass of 1 carat.

 @item GSL_CONST_MKSA_GRAM_FORCE
 The force of 1 gram weight.

 @item GSL_CONST_MKSA_POUND_FORCE
 The force of 1 pound weight.

 @item GSL_CONST_MKSA_KILOPOUND_FORCE
 The force of 1 kilopound weight.

 @item GSL_CONST_MKSA_POUNDAL
 The force of 1 poundal.
 @end table


 @node Thermal Energy and Power
 @section Thermal Energy and Power
 @cindex energy, units of
 @cindex power, units of
 @cindex thermal energy, units of
 @table @code
 @item GSL_CONST_MKSA_CALORIE
 The energy of 1 calorie.

 @item GSL_CONST_MKSA_BTU
 The energy of 1 British Thermal Unit, @math{btu}.

 @item GSL_CONST_MKSA_THERM
 The energy of 1 Therm.

 @item GSL_CONST_MKSA_HORSEPOWER
 The power of 1 horsepower.
 @end table


 @node Pressure
 @section Pressure
 @cindex pressure, units of
 @table @code
 @item GSL_CONST_MKSA_BAR
 The pressure of 1 bar.

 @item GSL_CONST_MKSA_STD_ATMOSPHERE
 The pressure of 1 standard atmosphere.

 @item GSL_CONST_MKSA_TORR
 The pressure of 1 torr.

 @item GSL_CONST_MKSA_METER_OF_MERCURY
 The pressure of 1 meter of mercury.

 @item GSL_CONST_MKSA_INCH_OF_MERCURY
 The pressure of 1 inch of mercury.

 @item GSL_CONST_MKSA_INCH_OF_WATER
 The pressure of 1 inch of water.

 @item GSL_CONST_MKSA_PSI
 The pressure of 1 pound per square inch.
 @end table

 @node Viscosity
 @section Viscosity
 @cindex viscosity, units of
 @table @code
 @item GSL_CONST_MKSA_POISE
 The dynamic viscosity of 1 poise.

 @item GSL_CONST_MKSA_STOKES
 The kinematic viscosity of 1 stokes.
 @end table


 @node Light and Illumination
 @section Light and Illumination
 @cindex light, units of
 @cindex illumination, units of

 @table @code
 @item GSL_CONST_MKSA_STILB
 The luminance of 1 stilb.

 @item GSL_CONST_MKSA_LUMEN
 The luminous flux of 1 lumen.

 @item GSL_CONST_MKSA_LUX
 The illuminance of 1 lux.

 @item GSL_CONST_MKSA_PHOT
 The illuminance of 1 phot.

 @item GSL_CONST_MKSA_FOOTCANDLE
 The illuminance of 1 footcandle.

 @item GSL_CONST_MKSA_LAMBERT
 The luminance of 1 lambert.

 @item GSL_CONST_MKSA_FOOTLAMBERT
 The luminance of 1 footlambert.
 @end table


 @node Radioactivity
 @section Radioactivity
 @cindex radioactivity, units of
 @table @code
 @item GSL_CONST_MKSA_CURIE
 The activity of 1 curie.

 @item GSL_CONST_MKSA_ROENTGEN
 The exposure of 1 roentgen.

 @item GSL_CONST_MKSA_RAD
 The absorbed dose of 1 rad.
 @end table


 @node Force and Energy
 @section Force and Energy
 @cindex force and energy, units of
 @table @code
 @item GSL_CONST_MKSA_NEWTON
 The SI unit of force, 1 Newton.

 @item GSL_CONST_MKSA_DYNE
 The force of 1 Dyne = @c{$10^{-5}$}
 @math{10^-5} Newton.

 @item GSL_CONST_MKSA_JOULE
 The SI unit of energy, 1 Joule.

 @item GSL_CONST_MKSA_ERG
 The energy 1 erg = @c{$10^{-7}$}
 @math{10^-7} Joule.
 @end table


 @node Prefixes
 @section Prefixes
 @cindex prefixes
 @cindex constants, prefixes

 These constants are dimensionless scaling factors.

 @table @code
 @item GSL_CONST_NUM_YOTTA
 @c{$10^{24}$}
 @math{10^24}

 @item GSL_CONST_NUM_ZETTA
 @c{$10^{21}$}
 @math{10^21}

 @item GSL_CONST_NUM_EXA
 @c{$10^{18}$}
 @math{10^18}

 @item GSL_CONST_NUM_PETA
 @c{$10^{15}$}
 @math{10^15}

 @item GSL_CONST_NUM_TERA
 @c{$10^{12}$}
 @math{10^12}

 @item GSL_CONST_NUM_GIGA
 @math{10^9}

 @item GSL_CONST_NUM_MEGA
 @math{10^6}

 @item GSL_CONST_NUM_KILO
 @math{10^3}

 @item GSL_CONST_NUM_MILLI
 @c{$10^{-3}$}
 @math{10^-3}

 @item GSL_CONST_NUM_MICRO
 @c{$10^{-6}$}
 @math{10^-6}

 @item GSL_CONST_NUM_NANO
 @c{$10^{-9}$}
 @math{10^-9}

 @item GSL_CONST_NUM_PICO
 @c{$10^{-12}$}
 @math{10^-12}

 @item GSL_CONST_NUM_FEMTO
 @c{$10^{-15}$}
 @math{10^-15}

 @item GSL_CONST_NUM_ATTO
 @c{$10^{-18}$}
 @math{10^-18}

 @item GSL_CONST_NUM_ZEPTO
 @c{$10^{-21}$}
 @math{10^-21}

 @item GSL_CONST_NUM_YOCTO
 @c{$10^{-24}$}
 @math{10^-24}
 @end table

 @node Physical Constant Examples
 @section Examples

 The following program demonstrates the use of the physical constants in
 a calculation.  In this case, the goal is to calculate the range of
 light-travel times from Earth to Mars.

 The required data is the average distance of each planet from the Sun in
 astronomical units (the eccentricities and inclinations of the orbits
 will be neglected for the purposes of this calculation).  The average
 radius of the orbit of Mars is 1.52 astronomical units, and for the
 orbit of Earth it is 1 astronomical unit (by definition).  These values
 are combined with the MKSA values of the constants for the speed of
 light and the length of an astronomical unit to produce a result for the
 shortest and longest light-travel times in seconds.  The figures are
 converted into minutes before being displayed.

 @example
 @verbatiminclude examples/const.c
 @end example

 @noindent
 Here is the output from the program,

 @example
 @verbatiminclude examples/const.out
 @end example

 @node Physical Constant References and Further Reading
 @section References and Further Reading

 The authoritative sources for physical constants are the 2002 CODATA
 recommended values, published in the articles below. Further information
 on the values of physical constants is also available from the cited
 articles and the NIST website.

 @itemize @asis
 @item Journal of Physical and Chemical Reference Data, 28(6), 1713-1852, 1999
 @item Reviews of Modern Physics, 72(2), 351-495, 2000
 @item @uref{http://www.physics.nist.gov/cuu/Constants/index.html}
 @item @uref{http://physics.nist.gov/Pubs/SP811/appenB9.html}
 @end itemize
	@cindex physical constants
	@cindex constants, physical
	@cindex conversion of units
	@cindex units, conversion of
	This chapter describes macros for the values of physical constants, such
	as the speed of light, @math{c}, and gravitational constant, @math{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.

	The definitions of constants in the MKSA system are available in the file
	@file{gsl_const_mksa.h}. The constants in the CGSM system are defined in
	@file{gsl_const_cgsm.h}. Dimensionless constants, such as the fine
	structure constant, which are pure numbers are defined in
	@file{gsl_const_num.h}.

	@menu
	* Fundamental Constants::
	* Astronomy and Astrophysics::
	* Atomic and Nuclear Physics::
	* Measurement of Time::
	* Imperial Units ::
	* Speed and Nautical Units::
	* Printers Units::
	* Volume Area and Length::
	* Mass and Weight ::
	* Thermal Energy and Power::
	* Pressure::
	* Viscosity::
	* Light and Illumination::
	* Radioactivity::
	* Force and Energy::
	* Prefixes::
	* Physical Constant Examples::
	* Physical Constant References and Further Reading::
	@end menu

	The full list of constants is described briefly below. Consult the
	header files themselves for the values of the constants used in the
	library.

	@node Fundamental Constants
	@section Fundamental Constants
	@cindex fundamental constants
	@cindex constants, fundamental
	@table @code
	@item GSL_CONST_MKSA_SPEED_OF_LIGHT
	The speed of light in vacuum, @math{c}.

	@item GSL_CONST_MKSA_VACUUM_PERMEABILITY
	The permeability of free space, @math{\mu_0}. This constant is defined
	in the MKSA system only.

	@item GSL_CONST_MKSA_VACUUM_PERMITTIVITY
	The permittivity of free space, @math{\epsilon_0}. This constant is
	defined in the MKSA system only.

	@item GSL_CONST_MKSA_PLANCKS_CONSTANT_H
	Planck's constant, @math{h}.

	@item GSL_CONST_MKSA_PLANCKS_CONSTANT_HBAR
	Planck's constant divided by @math{2\pi}, @math{\hbar}.

	@item GSL_CONST_NUM_AVOGADRO
	Avogadro's number, @math{N_a}.

	@item GSL_CONST_MKSA_FARADAY
	The molar charge of 1 Faraday.

	@item GSL_CONST_MKSA_BOLTZMANN
	The Boltzmann constant, @math{k}.

	@item GSL_CONST_MKSA_MOLAR_GAS
	The molar gas constant, @math{R_0}.

	@item GSL_CONST_MKSA_STANDARD_GAS_VOLUME
	The standard gas volume, @math{V_0}.

	@item GSL_CONST_MKSA_STEFAN_BOLTZMANN_CONSTANT
	The Stefan-Boltzmann radiation constant, @math{\sigma}.

	@item GSL_CONST_MKSA_GAUSS
	The magnetic field of 1 Gauss.
	@end table

	@node Astronomy and Astrophysics
	@section Astronomy and Astrophysics
	@cindex astronomical constants
	@table @code
	@item GSL_CONST_MKSA_ASTRONOMICAL_UNIT
	The length of 1 astronomical unit (mean earth-sun distance), @math{au}.

	@item GSL_CONST_MKSA_GRAVITATIONAL_CONSTANT
	The gravitational constant, @math{G}.

	@item GSL_CONST_MKSA_LIGHT_YEAR
	The distance of 1 light-year, @math{ly}.

	@item GSL_CONST_MKSA_PARSEC
	The distance of 1 parsec, @math{pc}.

	@item GSL_CONST_MKSA_GRAV_ACCEL
	The standard gravitational acceleration on Earth, @math{g}.

	@item GSL_CONST_MKSA_SOLAR_MASS
	The mass of the Sun.
	@end table

	@node Atomic and Nuclear Physics
	@section Atomic and Nuclear Physics
	@cindex atomic physics, constants
	@cindex nuclear physics, constants
	@table @code
	@item GSL_CONST_MKSA_ELECTRON_CHARGE
	The charge of the electron, @math{e}.

	@item GSL_CONST_MKSA_ELECTRON_VOLT
	The energy of 1 electron volt, @math{eV}.

	@item GSL_CONST_MKSA_UNIFIED_ATOMIC_MASS
	The unified atomic mass, @math{amu}.

	@item GSL_CONST_MKSA_MASS_ELECTRON
	The mass of the electron, @math{m_e}.

	@item GSL_CONST_MKSA_MASS_MUON
	The mass of the muon, @math{m_\mu}.

	@item GSL_CONST_MKSA_MASS_PROTON
	The mass of the proton, @math{m_p}.

	@item GSL_CONST_MKSA_MASS_NEUTRON
	The mass of the neutron, @math{m_n}.

	@item GSL_CONST_NUM_FINE_STRUCTURE
	The electromagnetic fine structure constant @math{\alpha}.

	@item GSL_CONST_MKSA_RYDBERG
	The Rydberg constant, @math{Ry}, in units of energy. This is related to
	the Rydberg inverse wavelength @math{R} by @math{Ry = h c R}.

	@item GSL_CONST_MKSA_BOHR_RADIUS
	The Bohr radius, @math{a_0}.

	@item GSL_CONST_MKSA_ANGSTROM
	The length of 1 angstrom.

	@item GSL_CONST_MKSA_BARN
	The area of 1 barn.

	@item GSL_CONST_MKSA_BOHR_MAGNETON
	The Bohr Magneton, @math{\mu_B}.

	@item GSL_CONST_MKSA_NUCLEAR_MAGNETON
	The Nuclear Magneton, @math{\mu_N}.

	@item GSL_CONST_MKSA_ELECTRON_MAGNETIC_MOMENT
	The absolute value of the magnetic moment of the electron, @math{\mu_e}.
	The physical magnetic moment of the electron is negative.

	@item GSL_CONST_MKSA_PROTON_MAGNETIC_MOMENT
	The magnetic moment of the proton, @math{\mu_p}.

	@item GSL_CONST_MKSA_THOMSON_CROSS_SECTION
	The Thomson cross section, @math{\sigma_T}.

	@item GSL_CONST_MKSA_DEBYE
	The electric dipole moment of 1 Debye, @math{D}.
	@end table


	@node Measurement of Time
	@section Measurement of Time
	@cindex time units
	@table @code
	@item GSL_CONST_MKSA_MINUTE
	The number of seconds in 1 minute.

	@item GSL_CONST_MKSA_HOUR
	The number of seconds in 1 hour.

	@item GSL_CONST_MKSA_DAY
	The number of seconds in 1 day.

	@item GSL_CONST_MKSA_WEEK
	The number of seconds in 1 week.
	@end table


	@node Imperial Units
	@section Imperial Units
	@cindex imperial units
	@cindex units, imperial
	@table @code
	@item GSL_CONST_MKSA_INCH
	The length of 1 inch.

	@item GSL_CONST_MKSA_FOOT
	The length of 1 foot.

	@item GSL_CONST_MKSA_YARD
	The length of 1 yard.

	@item GSL_CONST_MKSA_MILE
	The length of 1 mile.

	@item GSL_CONST_MKSA_MIL
	The length of 1 mil (1/1000th of an inch).
	@end table


	@node Speed and Nautical Units
	@section Speed and Nautical Units
	@cindex nautical units

	@table @code
	@item GSL_CONST_MKSA_KILOMETERS_PER_HOUR
	The speed of 1 kilometer per hour.

	@item GSL_CONST_MKSA_MILES_PER_HOUR
	The speed of 1 mile per hour.

	@item GSL_CONST_MKSA_NAUTICAL_MILE
	The length of 1 nautical mile.

	@item GSL_CONST_MKSA_FATHOM
	The length of 1 fathom.

	@item GSL_CONST_MKSA_KNOT
	The speed of 1 knot.
	@end table


	@node Printers Units
	@section Printers Units
	@cindex printers units

	@table @code
	@item GSL_CONST_MKSA_POINT
	The length of 1 printer's point (1/72 inch).

	@item GSL_CONST_MKSA_TEXPOINT
	The length of 1 TeX point (1/72.27 inch).
	@end table


	@node Volume Area and Length
	@section Volume, Area and Length
	@cindex volume units

	@table @code
	@item GSL_CONST_MKSA_MICRON
	The length of 1 micron.

	@item GSL_CONST_MKSA_HECTARE
	The area of 1 hectare.

	@item GSL_CONST_MKSA_ACRE
	The area of 1 acre.

	@item GSL_CONST_MKSA_LITER
	The volume of 1 liter.

	@item GSL_CONST_MKSA_US_GALLON
	The volume of 1 US gallon.

	@item GSL_CONST_MKSA_CANADIAN_GALLON
	The volume of 1 Canadian gallon.

	@item GSL_CONST_MKSA_UK_GALLON
	The volume of 1 UK gallon.

	@item GSL_CONST_MKSA_QUART
	The volume of 1 quart.

	@item GSL_CONST_MKSA_PINT
	The volume of 1 pint.
	@end table


	@comment @node Cookery
	@comment @section Cookery
	@comment @commentindex cookery units

	@comment @table @commentode
	@comment @item GSL_CONST_MKSA_CUP
	@comment The volume of 1 cup.

	@comment @item GSL_CONST_MKSA_FLUID_OUNCE
	@comment The volume of 1 fluid ounce.

	@comment @item GSL_CONST_MKSA_TABLESPOON
	@comment The volume of 1 tablespoon.

	@comment @item GSL_CONST_MKSA_TEASPOON
	@comment The volume of 1 teaspoon.
	@comment @end table


	@node Mass and Weight
	@section Mass and Weight
	@cindex mass, units of
	@cindex weight, units of
	@table @code
	@item GSL_CONST_MKSA_POUND_MASS
	The mass of 1 pound.

	@item GSL_CONST_MKSA_OUNCE_MASS
	The mass of 1 ounce.

	@item GSL_CONST_MKSA_TON
	The mass of 1 ton.

	@item GSL_CONST_MKSA_METRIC_TON
	The mass of 1 metric ton (1000 kg).

	@item GSL_CONST_MKSA_UK_TON
	The mass of 1 UK ton.

	@item GSL_CONST_MKSA_TROY_OUNCE
	The mass of 1 troy ounce.

	@item GSL_CONST_MKSA_CARAT
	The mass of 1 carat.

	@item GSL_CONST_MKSA_GRAM_FORCE
	The force of 1 gram weight.

	@item GSL_CONST_MKSA_POUND_FORCE
	The force of 1 pound weight.

	@item GSL_CONST_MKSA_KILOPOUND_FORCE
	The force of 1 kilopound weight.

	@item GSL_CONST_MKSA_POUNDAL
	The force of 1 poundal.
	@end table


	@node Thermal Energy and Power
	@section Thermal Energy and Power
	@cindex energy, units of
	@cindex power, units of
	@cindex thermal energy, units of
	@table @code
	@item GSL_CONST_MKSA_CALORIE
	The energy of 1 calorie.

	@item GSL_CONST_MKSA_BTU
	The energy of 1 British Thermal Unit, @math{btu}.

	@item GSL_CONST_MKSA_THERM
	The energy of 1 Therm.

	@item GSL_CONST_MKSA_HORSEPOWER
	The power of 1 horsepower.
	@end table


	@node Pressure
	@section Pressure
	@cindex pressure, units of
	@table @code
	@item GSL_CONST_MKSA_BAR
	The pressure of 1 bar.

	@item GSL_CONST_MKSA_STD_ATMOSPHERE
	The pressure of 1 standard atmosphere.

	@item GSL_CONST_MKSA_TORR
	The pressure of 1 torr.

	@item GSL_CONST_MKSA_METER_OF_MERCURY
	The pressure of 1 meter of mercury.

	@item GSL_CONST_MKSA_INCH_OF_MERCURY
	The pressure of 1 inch of mercury.

	@item GSL_CONST_MKSA_INCH_OF_WATER
	The pressure of 1 inch of water.

	@item GSL_CONST_MKSA_PSI
	The pressure of 1 pound per square inch.
	@end table

	@node Viscosity
	@section Viscosity
	@cindex viscosity, units of
	@table @code
	@item GSL_CONST_MKSA_POISE
	The dynamic viscosity of 1 poise.

	@item GSL_CONST_MKSA_STOKES
	The kinematic viscosity of 1 stokes.
	@end table


	@node Light and Illumination
	@section Light and Illumination
	@cindex light, units of
	@cindex illumination, units of

	@table @code
	@item GSL_CONST_MKSA_STILB
	The luminance of 1 stilb.

	@item GSL_CONST_MKSA_LUMEN
	The luminous flux of 1 lumen.

	@item GSL_CONST_MKSA_LUX
	The illuminance of 1 lux.

	@item GSL_CONST_MKSA_PHOT
	The illuminance of 1 phot.

	@item GSL_CONST_MKSA_FOOTCANDLE
	The illuminance of 1 footcandle.

	@item GSL_CONST_MKSA_LAMBERT
	The luminance of 1 lambert.

	@item GSL_CONST_MKSA_FOOTLAMBERT
	The luminance of 1 footlambert.
	@end table


	@node Radioactivity
	@section Radioactivity
	@cindex radioactivity, units of
	@table @code
	@item GSL_CONST_MKSA_CURIE
	The activity of 1 curie.

	@item GSL_CONST_MKSA_ROENTGEN
	The exposure of 1 roentgen.

	@item GSL_CONST_MKSA_RAD
	The absorbed dose of 1 rad.
	@end table


	@node Force and Energy
	@section Force and Energy
	@cindex force and energy, units of
	@table @code
	@item GSL_CONST_MKSA_NEWTON
	The SI unit of force, 1 Newton.

	@item GSL_CONST_MKSA_DYNE
	The force of 1 Dyne = @c{$10^{-5}$}
	@math{10^-5} Newton.

	@item GSL_CONST_MKSA_JOULE
	The SI unit of energy, 1 Joule.

	@item GSL_CONST_MKSA_ERG
	The energy 1 erg = @c{$10^{-7}$}
	@math{10^-7} Joule.
	@end table


	@node Prefixes
	@section Prefixes
	@cindex prefixes
	@cindex constants, prefixes

	These constants are dimensionless scaling factors.

	@table @code
	@item GSL_CONST_NUM_YOTTA
	@c{$10^{24}$}
	@math{10^24}

	@item GSL_CONST_NUM_ZETTA
	@c{$10^{21}$}
	@math{10^21}

	@item GSL_CONST_NUM_EXA
	@c{$10^{18}$}
	@math{10^18}

	@item GSL_CONST_NUM_PETA
	@c{$10^{15}$}
	@math{10^15}

	@item GSL_CONST_NUM_TERA
	@c{$10^{12}$}
	@math{10^12}

	@item GSL_CONST_NUM_GIGA
	@math{10^9}

	@item GSL_CONST_NUM_MEGA
	@math{10^6}

	@item GSL_CONST_NUM_KILO
	@math{10^3}

	@item GSL_CONST_NUM_MILLI
	@c{$10^{-3}$}
	@math{10^-3}

	@item GSL_CONST_NUM_MICRO
	@c{$10^{-6}$}
	@math{10^-6}

	@item GSL_CONST_NUM_NANO
	@c{$10^{-9}$}
	@math{10^-9}

	@item GSL_CONST_NUM_PICO
	@c{$10^{-12}$}
	@math{10^-12}

	@item GSL_CONST_NUM_FEMTO
	@c{$10^{-15}$}
	@math{10^-15}

	@item GSL_CONST_NUM_ATTO
	@c{$10^{-18}$}
	@math{10^-18}

	@item GSL_CONST_NUM_ZEPTO
	@c{$10^{-21}$}
	@math{10^-21}

	@item GSL_CONST_NUM_YOCTO
	@c{$10^{-24}$}
	@math{10^-24}
	@end table

	@node Physical Constant Examples
	@section Examples

	The following program demonstrates the use of the physical constants in
	a calculation. In this case, the goal is to calculate the range of
	light-travel times from Earth to Mars.

	The required data is the average distance of each planet from the Sun in
	astronomical units (the eccentricities and inclinations of the orbits
	will be neglected for the purposes of this calculation). The average
	radius of the orbit of Mars is 1.52 astronomical units, and for the
	orbit of Earth it is 1 astronomical unit (by definition). These values
	are combined with the MKSA values of the constants for the speed of
	light and the length of an astronomical unit to produce a result for the
	shortest and longest light-travel times in seconds. The figures are
	converted into minutes before being displayed.

	@example
	@verbatiminclude examples/const.c
	@end example

	@noindent
	Here is the output from the program,

	@example
	@verbatiminclude examples/const.out
	@end example

	@node Physical Constant References and Further Reading
	@section References and Further Reading

	The authoritative sources for physical constants are the 2002 CODATA
	recommended values, published in the articles below. Further information
	on the values of physical constants is also available from the cited
	articles and the NIST website.

	@itemize @asis
	@item Journal of Physical and Chemical Reference Data, 28(6), 1713-1852, 1999
	@item Reviews of Modern Physics, 72(2), 351-495, 2000
	@item @uref{http://www.physics.nist.gov/cuu/Constants/index.html}
	@item @uref{http://physics.nist.gov/Pubs/SP811/appenB9.html}
	@end itemize