Title: Physical Constants

The GSL physical constants are defined as Ruby constants under the modules

GSL::CONST::MKSA (MKSA unit)
GSL::CONST:CGSM (CGSM unit)
GSL::CONST:NUM (Dimension-less constants)

For example, the GSL C constant GSL_CONST_MKSA_SPEED_OF_LIGHT is represented by a Ruby constant,

GSL_CONST_MKSA_SPEED_OF_LIGHT  ---> GSL::CONST::MKSA::SPEED_OF_LIGHT

The following lists a part of the constants. Most of the constants are defined both in the modules GSL::CONST::MKSA and GSL::CONST::CGSM. See also the GSL reference

1 Fundamental Constants

GSL::CONST::MKSA::SPEED_OF_LIGHT: The speed of light in vacuum, c.
GSL::CONST::MKSA::VACUUM_PERMEABILITY: The permeability of free space, \mu (not defined in GSL::CONST::CGSM).
GSL::CONST::MKSA::VACUUM_PERMITTIVITY: The permittivity of free space, \epsilon_0 (not defined in GSL::CONST::CGSM).
GSL::CONST::MKSA::PLANCKS_CONSTANT_H: Planck's constant, h.
GSL::CONST::MKSA::PLANCKS_CONSTANT_HBAR: Planck's constant divided by 2\pi, \hbar.
GSL::CONST::NUM::AVOGADRO: Avogadro's number
GSL::CONST::MKSA::FARADAY: The molar charge of 1 Faraday.
GSL::CONST::MKSA::BOLTZMANN: The Boltzmann constant, k.
GSL::CONST::MKSA::STEFAN_BOLTZMANN_CONSTANT: The Stefan-Boltzmann constant, \sigma.
GSL::CONST::MKSA::MOLAR_GAS: The molar gas constant, R_0.
GSL::CONST::MKSA::STANDARD_GAS_VOLUME: The standard gas volume, V_0.
GSL::CONST::MKSA::GAUSS: The magnetic field of 1 Gauss.

2 Astronomy and Astrophysics

GSL::CONST::MKSA::ASTRONOMICAL_UNIT: The length of 1 astronomical unit (mean earth-sun distance), AU.
GSL::CONST::MKSA::GRAVITATIONAL_CONSTANT: The gravitational constant, G.
GSL::CONST::MKSA::LIGHT_YEAR: The distance of 1 light-year, ly.
GSL::CONST::MKSA::PARSEC: The distance of 1 parsec, pc.
GSL::CONST::MKSA::GRAV_ACCEL: The standard gravitational acceleration on Earth, g.
GSL::CONST::MKSA::SOLAR_MASS: The mass of the Sun.

3 Atomic and Nuclear Physics

GSL::CONST::MKSA::ELECTRON_CHARGE: The charge of the electron, e.
GSL::CONST::CGSM::ELECTRON_CHARGE_ESU: The charge of the electron, e, in esu unit (not defined in GSL::CONST::MKSA).
GSL::CONST::MKSA::ELECTRON_VOLT: The energy of 1 electron volt, eV.
GSL::CONST::MKSA::UNIFIED_ATOMIC_MASS: The unified atomic mass, amu.
GSL::CONST::MKSA::MASS_ELECTRON: The mass of the electron, m_e.
GSL::CONST::MKSA::MASS_MUON: The mass of the muon, m_\mu.
GSL::CONST::MKSA::MASS_PROTON: The mass of the proton, m_p.
GSL::CONST::MKSA::MASS_NEUTRON: The mass of the proton, m_n.
GSL::CONST::NUM::FINE_STRUCTURE: The electromagnetic fine structure constant alpha.
GSL::CONST::MKSA::RYDBERG: The Rydberg constant, Ry, in units of energy. This is related to the Rydberg inverse wavelength R by Ry = h c R.
GSL::CONST::MKSA::THOMSON_CROSS_SECTION: The Thomson cross section of photon scattering by electrons.
GSL::CONST::MKSA::BOHR_RADIUS: The Bohr radius, a_0.
GSL::CONST::MKSA::ANGSTROM: The length of 1 angstrom.
GSL::CONST::MKSA::BARN: The area of 1 barn.
GSL::CONST::MKSA::BOHR_MAGNETON: The Bohr Magneton, mu_B.
GSL::CONST::MKSA::NUCLEAR_MAGNETON: The Nuclear Magneton, mu_N.
GSL::CONST::MKSA::ELECTRON_MAGNETIC_MOMENT: The absolute value of the magnetic moment of the electron, mu_e. The physical magnetic moment of the electron is negative.
GSL::CONST::MKSA::PROTON_MAGNETIC_MOMENT: The magnetic moment of the proton, mu_p.

4 Measurement of Time

GSL::CONST::MKSA::MINUTE: The number of seconds in 1 minute.
GSL::CONST::MKSA::HOUR: The number of seconds in 1 hour.
GSL::CONST::MKSA::DAY: The number of seconds in 1 day.
GSL::CONST::MKSA::WEEK: The number of seconds in 1 week.

5 Imperial Units

GSL::CONST::MKSA::INCH: The length of 1 inch.
GSL::CONST::MKSA::FOOT: The length of 1 foot.
GSL::CONST::MKSA::YARD: The length of 1 yard.
GSL::CONST::MKSA::MILE: The length of 1 mile.
GSL::CONST::MKSA::MIL: The length of 1 mil (1/1000th of an inch).

6 Nautical Units

GSL::CONST::MKSA::NAUTICAL_MILE: The length of 1 nautical mile.
GSL::CONST::MKSA::FATHOM: The length of 1 fathom.
GSL::CONST::MKSA::KNOT: The speed of 1 knot.

7 Printers Units

GSL::CONST::MKSA::POINT: The length of 1 printer's point (1/72 inch).
GSL::CONST::MKSA::TEXPOINT: The length of 1 TeX point (1/72.27 inch).

8 Volume

GSL::CONST::MKSA::ACRE: The area of 1 acre.
GSL::CONST::MKSA::LITER: The volume of 1 liter.
GSL::CONST::MKSA::US_GALLON: The volume of 1 US gallon.
GSL::CONST::MKSA::CANADIAN_GALLON: The volume of 1 Canadian gallon.
GSL::CONST::MKSA::UK_GALLON: The volume of 1 UK gallon.
GSL::CONST::MKSA::QUART: The volume of 1 quart.
GSL::CONST::MKSA::PINT: The volume of 1 pint.

9 Mass and Weigth

GSL::CONST::MKSA::POUND_MASS: The mass of 1 pound.
GSL::CONST::MKSA::OUNCE_MASS: The mass of 1 ounce.
GSL::CONST::MKSA::TON: The mass of 1 ton.
GSL::CONST::MKSA::METRIC_TON: The mass of 1 metric ton (1000 kg).
GSL::CONST::MKSA::UK_TON: The mass of 1 UK ton.
GSL::CONST::MKSA::TROY_OUNCE: The mass of 1 troy ounce.
GSL::CONST::MKSA::CARAT: The mass of 1 carat.
GSL::CONST::MKSA::GRAM_FORCE: The force of 1 gram weight.
GSL::CONST::MKSA::POUND_FORCE: The force of 1 pound weight.
GSL::CONST::MKSA::KILOPOUND_FORCE: The force of 1 kilopound weight.
GSL::CONST::MKSA::POUNDAL: The force of 1 poundal.

10 Thermal Energy and Power

GSL::CONST::MKSA::CALORIE: The energy of 1 calorie.
GSL::CONST::MKSA::BTU: The energy of 1 British Thermal Unit, btu.
GSL::CONST::MKSA::THERM: The energy of 1 Therm.
GSL::CONST::MKSA::HORSEPOWER: The power of 1 horsepower.

11 Pressure

GSL::CONST::MKSA::BAR: The pressure of 1 bar.
GSL::CONST::MKSA::STD_ATMOSPHERE: The pressure of 1 standard atmosphere.
GSL::CONST::MKSA::TORR: The pressure of 1 torr.
GSL::CONST::MKSA::METER_OF_MERCURY: The pressure of 1 meter of mercury.
GSL::CONST::MKSA::INCH_OF_MERCURY: The pressure of 1 inch of mercury.
GSL::CONST::MKSA::INCH_OF_WATER: The pressure of 1 inch of water.
GSL::CONST::MKSA::PSI: The pressure of 1 pound per square inch.

12 Viscosity

GSL::CONST::MKSA::POISE: The dynamic viscosity of 1 poise.
GSL::CONST::MKSA::STOKES: The kinematic viscosity of 1 stokes.

13 Light and Illumination

GSL::CONST::MKSA::STILB: The luminance of 1 stilb.
GSL::CONST::MKSA::LUMEN: The luminous flux of 1 lumen.
GSL::CONST::MKSA::LUX: The illuminance of 1 lux.
GSL::CONST::MKSA::PHOT: The illuminance of 1 phot.
GSL::CONST::MKSA::FOOTCANDLE: The illuminance of 1 footcandle.
GSL::CONST::MKSA::LAMBERT: The luminance of 1 lambert.
GSL::CONST::MKSA::FOOTLAMBERT: The luminance of 1 footlambert.

14 Radioactivity

GSL::CONST::MKSA::CURIE: The activity of 1 curie.
GSL::CONST::MKSA::ROENTGEN: The exposure of 1 roentgen.
GSL::CONST::MKSA::RAD: The absorbed dose of 1 rad.

15 Force and Energy

GSL::CONST::MKSA::NEWTON: The SI unit of force, 1 Newton.
GSL::CONST::MKSA::DYNE: he force of 1 Dyne = 10^-5 Newton.
GSL::CONST::MKSA::JOULE: The SI unit of energy, 1 Joule.
GSL::CONST::MKSA::ERG: The energy 1 erg = 10^-7 Joule.

16 Prefixes

GSL::CONST::NUM::YOTTA: 10^24
GSL::CONST::NUM::ZETTA: 10^21
GSL::CONST::NUM::EXA: 10^18
GSL::CONST::NUM::PETA: 10^15
GSL::CONST::NUM::TERA: 10^12
GSL::CONST::NUM::GIGA: 10^9
GSL::CONST::NUM::MEGA: 10^6
GSL::CONST::NUM::KILO: 10^3
GSL::CONST::NUM::MILLI: 10^-3
GSL::CONST::NUM::MICRO: 10^-6
GSL::CONST::NUM::NANO: 10^-9
GSL::CONST::NUM::PICO: 10^-12
GSL::CONST::NUM::FEMTO: 10^-15
GSL::CONST::NUM::ATTO: 10^-18
GSL::CONST::NUM::ZEPTO: 10^-21
GSL::CONST::NUM::YOCTO: 10^-24

16.1 Example

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.

require("gsl")
include GSL::CONST::MKSA

puts("In MKSA unit")

c  = SPEED_OF_LIGHT;
au = ASTRONOMICAL_UNIT;
minutes = MINUTE;

# distance stored in meters 
r_earth = 1.00 * au;  
r_mars  = 1.52 * au;

t_min = (r_mars - r_earth) / c;
t_max = (r_mars + r_earth) / c;

printf("light travel time from Earth to Mars:\n");
printf("c = %e [m/s]\n", c)
printf("AU = %e [m]\n", au)
printf("minutes = %e [s]\n", minutes)
printf("minimum = %.1f minutes\n", t_min / minutes);
printf("maximum = %.1f minutes\n\n", t_max / minutes);

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