Constants

This module provides a collection of physical constants in the MKSA system.

The constants are defined in the module files themselves, and are not imported by default.

Usage

import vsl.consts

println(consts.mksa_speed_of_light)

Fundamental Constants

consts.mksa_speed_of_light

The speed of light in vacuum.

consts.mksa_vacuum_permeability

The permeability of free space, μ_0. This constant is defined in the MKSA system only.

consts.mksa_vacuum_permittivity

The permittivity of free space, \epsilon_0. This constant is defined in the MKSA system only.

consts.mksa_plancks_constant_h

Planck's constant, h.

consts.mksa_plancks_constant_hbar

Planck's constant divided by 2\pi, \hbar.

consts.num_avogadro

Avogadro's number, N_a.

consts.mksa_faraday

The molar charge of 1 Faraday.

consts.mksa_boltzmann

The Boltzmann constant, k.

consts.mksa_molar_gas

The molar gas constant, R_0.

consts.mksa_standard_gas_volume

The standard gas volume, V_0.

consts.mksa_stefan_boltzmann_constant

The Stefan-Boltzmann radiation constant, \sigma.

consts.mksa_gauss

The magnetic field of 1 Gauss.

Astronomy and Astrophysics

consts.mksa_astronomical_unit

The length of 1 astronomical unit (mean earth-sun distance), au.

consts.mksa_gravitational_constant

The gravitational constant, G.

consts.mksa_light_year

The distance of 1 light-year, ly.

consts.mksa_parsec

The distance of 1 parsec, pc.

consts.mksa_grav_accel

The standard gravitational acceleration on Earth, g.

consts.mksa_solar_mass

The mass of the Sun.

Atomic and Nuclear Physics

consts.mksa_electron_charge

The charge of the electron, e.

consts.mksa_electron_volt

The energy of 1 electron volt, eV.

consts.mksa_unified_atomic_mass

The unified atomic mass, amu.

consts.mksa_mass_electron

The mass of the electron, m_e.

consts.mksa_mass_muon

The mass of the muon, m_μ.

consts.mksa_mass_proton

The mass of the proton, m_p.

consts.mksa_mass_neutron

The mass of the neutron, m_n.

consts.num_fine_structure

The electromagnetic fine structure constant \alpha.

consts.mksa_rydberg

The Rydberg constant, Ry, in units of energy. This is related to the Rydberg inverse wavelength R_\infty by Ry = h c R_\infty.

consts.mksa_bohr_radius

The Bohr radius, a_0.

consts.mksa_angstrom

The length of 1 angstrom.

consts.mksa_barn

The area of 1 barn.

consts.mksa_bohr_magneton

The Bohr Magneton, μ_B.

consts.mksa_nuclear_magneton

The Nuclear Magneton, μ_N.

consts.mksa_electron_magnetic_moment

The absolute value of the magnetic moment of the electron, μ_e. The physical magnetic moment of the electron is negative.

consts.mksa_proton_magnetic_moment

The magnetic moment of the proton, μ_p.

consts.mksa_thomson_cross_section

The Thomson cross section, \sigma_T.

consts.mksa_debye

The electric dipole moment of 1 Debye, D.

Measurement of Time

consts.mksa_minute

The number of seconds in 1 minute.

consts.mksa_hour

The number of seconds in 1 hour.

consts.mksa_day

The number of seconds in 1 day.

consts.mksa_week

The number of seconds in 1 week.

Imperial Units

consts.mksa_inch

The length of 1 inch.

consts.mksa_foot

The length of 1 foot.

consts.mksa_yard

The length of 1 yard.

consts.mksa_mile

The length of 1 mile.

consts.mksa_mil

The length of 1 mil (1/1000th of an inch).

Speed and Nautical Units

consts.mksa_kilometers_per_hour

The speed of 1 kilometer per hour.

consts.mksa_miles_per_hour

The speed of 1 mile per hour.

consts.mksa_nautical_mile

The length of 1 nautical mile.

consts.mksa_fathom

The length of 1 fathom.

consts.mksa_knot

The speed of 1 knot.

Printers Units

consts.mksa_point

The length of 1 printer's point (1/72 inch).

consts.mksa_texpoint

The length of 1 TeX point (1/72.27 inch).

Volume, Area and Length

consts.mksa_micron

The length of 1 micron.

consts.mksa_hectare

The area of 1 hectare.

consts.mksa_acre

The area of 1 acre.

consts.mksa_liter

The volume of 1 liter.

consts.mksa_us_gallon

The volume of 1 US gallon.

consts.mksa_canadian_gallon

The volume of 1 Canadian gallon.

consts.mksa_uk_gallon

The volume of 1 UK gallon.

consts.mksa_quart

The volume of 1 quart.

consts.mksa_pint

The volume of 1 pint.

Mass and Weight

consts.mksa_pound_mass

The mass of 1 pound.

consts.mksa_ounce_mass

The mass of 1 ounce.

consts.mksa_ton

The mass of 1 ton.

consts.mksa_metric_ton

The mass of 1 metric ton (1000 kg).

consts.mksa_uk_ton

The mass of 1 UK ton.

consts.mksa_troy_ounce

The mass of 1 troy ounce.

consts.mksa_carat

The mass of 1 carat.

consts.mksa_gram_force

The force of 1 gram weight.

consts.mksa_pound_force

The force of 1 pound weight.

consts.mksa_kilopound_force

The force of 1 kilopound weight.

consts.mksa_poundal

The force of 1 poundal.

Thermal Energy and Power

consts.mksa_calorie

The energy of 1 calorie.

consts.mksa_btu

The energy of 1 British Thermal Unit, btu.

consts.mksa_therm

The energy of 1 Therm.

consts.mksa_horsepower

The power of 1 horsepower.

Pressure

consts.mksa_bar

The pressure of 1 bar.

consts.mksa_std_atmosphere

The pressure of 1 standard atmosphere.

consts.mksa_torr

The pressure of 1 torr.

consts.mksa_meter_of_mercury

The pressure of 1 meter of mercury.

consts.mksa_inch_of_mercury

The pressure of 1 inch of mercury.

consts.mksa_inch_of_water

The pressure of 1 inch of water.

consts.mksa_psi

The pressure of 1 pound per square inch.

Viscosity

consts.mksa_poise

The dynamic viscosity of 1 poise.

consts.mksa_stokes

The kinematic viscosity of 1 stokes.

Light and Illumination

consts.mksa_stilb

The luminance of 1 stilb.

consts.mksa_lumen

The luminous flux of 1 lumen.

consts.mksa_lux

The illuminance of 1 lux.

consts.mksa_phot

The illuminance of 1 phot.

consts.mksa_footcandle

The illuminance of 1 footcandle.

consts.mksa_lambert

The luminance of 1 lambert.

consts.mksa_footlambert

The luminance of 1 footlambert.

Radioactivity

consts.mksa_curie

The activity of 1 curie.

consts.mksa_roentgen

The exposure of 1 roentgen.

consts.mksa_rad

The absorbed dose of 1 rad.

Force and Energy

consts.mksa_newton

The SI unit of force, 1 Newton.

consts.mksa_dyne

The force of 1 Dyne = 10^{-5} Newton.

consts.mksa_joule

The SI unit of energy, 1 Joule.

consts.mksa_erg

The energy 1 erg = 10^{-7} Joule.

Prefixes

These constants are dimensionless scaling factors.

consts.num_yotta

10^{24}

consts.num_zetta

10^{21}

consts.num_exa

10^{18}

consts.num_peta

10^{15}

consts.num_tera

10^{12}

consts.num_giga

10^9

consts.num_mega

10^6

consts.num_kilo

10^3

consts.num_milli

10^{-3}

consts.num_micro

10^{-6}

consts.num_vsl_nano

10^{-9}

consts.num_pico

10^{-12}

consts.num_femto

10^{-15}

consts.num_atto

10^{-18}

consts.num_zepto

10^{-21}

consts.num_yocto

10^{-24}

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.

module main

import vsl.consts

c := consts.mksa_speed_of_light
au := consts.mksa_astronomical_unit
minutes := consts.mksa_minute // distance stored in meters
r_earth := 1.0 * au
r_mars := 1.52 * au
t_min := (r_mars - r_earth) / c
t_max := (r_mars + r_earth) / c
min := t_min / minutes
max := t_max / minutes
println('light travel time from Earth to Mars:')
println('minimum = ${min} minutes')
println('maximum = ${max} minutes')

will print

light travel time from Earth to Mars:
minimum = 4.3 minutes
maximum = 21.0 minutes

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).