#Original Function Location: /themis/lib/dav_lib/public_library/latest/constants.dvrc
/themis/lib/dav_lib/library/constants.dvrc
Source Code for Function: "unithelp()" in "constants.dvrc" (Public)
constants_version=1.06
# Convert values to single precision when not known to 7 significant figures?
# Add sources to help function outputs?
pi = 3.14159265358979; # Only single precision - double in con structure
ignore = -32768;
# NOTE: To bypass the intermediate float bug and ensure double precision for the constants, the values are entered through the function atod
# Constants (mathematical and physical)
# Physical constants use CODATA 2006 values, from http://physics.nist.gov/cuu/Constants/
# SI/mks units for all physical constants
# Last modified 11-30-2010 by S.Marshall
# e = e (base of natural logarithm), phi = golden ratio (positive number such that phi/1 = 1/(phi - 1)),
# AU = astronomical unit (m), b = Wien wavelength displacement law constant (m K), c = speed of light (m/s;
# exact by definition), eps0 = electric constant (permittivity of free space; F/m), eV = electron volt (J),
# F = Faraday constant (C/mol), G = Newtonian gravitation constant (m^3/kg/s^2), g = standard
# acceleration due to gravity (m/s^2; exact), h = Planck constant (J*s), hbar = h-bar (J*s),
# k = Boltzmann constant (J/K), kG = Gaussian gravitational constant (AU^1.5/day; defined exactly),
# me = electron mass (kg), mn = neutron mass (kg), mp = proton mass (kg), mu = atomic mass constant (kg),
# mu0 = magnetic constant (permeability of free space; N/A^2; exact), NA = Avogadro constant (mol^-1),
# qe = elementary charge (C), R = ideal/molar gas constant (J/mol/K), sigma = Stefan-Boltzmann constant (W/m^2/K^4)
con = { e = atod("2.71828182845904524"), phi = atod("1.61803398874989485"), pi = atod("3.14159265358979324"), AU = atod("1.49597870691e11"), b = atod("2.8977685e-3"), c = atod("299792458."), eps0 = atod("8.854187817e-12"), eV = atod("1.602176487e-19"), F = atod("96485.3399"), G = atod("6.67428e-11"), g = atod("9.80665"), h = atod("6.62606896e-34"), hbar = atod("1.054571628e-34"), k = atod("1.3806504e-23"), kG = atod("0.01720209895"), me = atod("9.10938215e-31"), mn = atod("1.674927211e-27"), mp = atod("1.672621637e-27"), mu = atod("1.660538782e-27"), mu0 = atod("12.566370614e-7"), NA = atod("6.02214179e23"), qe = atod("1.602176487e-19"), R = atod("8.314472"), sigma = atod("5.670400e-8") }
define conhelp(0) {
global(con)
if ($ARGC == 0) {
printf("\nconhelp() displays descriptions of all physical constants in structure con\n")
printf("S.Marshall 09-25-2009\n\n")
printf(" e = %.15f Base of natural logarithm\n", con.e)
printf(" phi = %.15f Golden ratio\n", con.phi)
printf(" pi = %.15f Pi\n\n", con.pi)
printf(" AU = %.11e m Astronomical unit\n\n", con.AU)
printf(" The following physical constants use the CODATA 2006 values,\n")
printf(" from http://physics.nist.gov/cuu/Constants\n")
printf(" and the JPL SSD values, from http://ssd.jpl.nasa.gov/?constants\n\n")
printf(" b = %.7e m*K Wien wavelength displacement law constant\n", con.b)
printf(" c = %d m/s Speed of light in a vacuum (exact)\n", con.c)
printf(" eps0 = %.9e F/m Electric constant (permittivity)\n", con.eps0)
printf(" eV = %.9e J Electron volt\n", con.eV)
printf(" F = %.4f C/mol Faraday constant\n", con.F)
printf(" G = %.5e m^3/kg/s^2 Newtonian gravitation constant\n", con.G)
printf(" g = %.5f m/s^2 Standard acceleration due to gravity (exact)\n", con.g)
printf(" h = %.8e J*s Planck constant\n", con.h)
printf(" hbar = %.9e J*s Reduced Planck constant (Dirac constant)\n", con.hbar)
printf(" k = %.7e J/K Boltzmann constant\n", con.k)
printf(" kG = %.11f AU^1.5/day Gaussian gravitational constant (NOT SI!)\n", con.kG)
printf(" me = %.8e kg Electron mass\n", con.me)
printf(" mn = %.9e kg Neutron mass\n", con.mn)
printf(" mp = %.9e kg Proton mass\n", con.mp)
printf(" mu = %.9e kg Atomic mass constant\n", con.mu)
printf(" mu0 = %.10e N/A^2 Magnetic constant (permeability)\n", con.mu0)
printf(" NA = %.8e mol^-1 Avogadro's number\n", con.NA)
printf(" qe = %.9e C Elementary charge\n", con.qe)
printf(" R = %.6f J/mol/K Ideal/molar gas constant\n", con.R)
printf(" sigma = %.6e W/m^2/K^4 Stefan-Boltzmann constant\n\n", con.sigma)
}
return(null)
}
# Astronomical constants:
# Most values from JPL SSD, http://ssd.jpl.nasa.gov/?phys_data
# or from NASA planetary fact sheets, http://nssdc.gsfc.nasa.gov/planetary/planetfact.html
# Current length of Earth's day from http://tycho.usno.navy.mil/leapsec.html
# Length of Earth's days, and Mars' days and years, from http://www.giss.nasa.gov/tools/mars24/help/notes.html
# Length of Earth's sidereal year from http://www.nasa.gov/worldbook/earth_worldbook.html
# Length of Earth's tropical year from http://scienceworld.wolfram.com/astronomy/TropicalYear.html (now 365.242189 days)
# Uncompressed densities here are a weighted average (to three significant figures) of values from three sources:
# http://geophysics.ou.edu/solid_earth/notes/planets.html,
# http://zebu.uoregon.edu/~imamura/121/lecture-4/density.html, and Phil's lectures
# GM values from http://ssd.jpl.nasa.gov/?phys_data, except Earth's from
# http://cddis.nasa.gov/926/egm96/doc/S11.HTML and Mars' from http://grctechlib.grc.nasa.gov/public/Digital/sg/MarsScout/Langley_trajectory_MRO.pdf
# SI/mks units unless noted otherwise
# Sun: GM = gravitational parameter (m^3/s^2); M = mass (kg), R = volumetric mean radius (m),
# rho = mean density (kg/m^3), kI = moment of inertia coefficient (I/MR^2, unitless),
# MV = absolute visual magnitude, L = luminosity (W), srp = sidereal rotation period at 16 deg latitude (s),
# T = effective surface temperature (K)
Sun = { GM = atod("1.32712440018e20"), M = atod("1.98842e30"), R = atod("696000000."), rho = atod("1408."), kI = atod("0.059"), MV = atod("4.83"), L = atod("3.846e26"), srp = atod("2.19283e6"), T = atod("5778.") }
# Planets/moons: GM = gravitational parameter (m^3/s^2); M = mass (kg); R = volumetric mean radius (m); Re = equatorial radius (m);
# Rp = polar radius (m); rho = mean density (kg/m^3); rhou = mean uncompressed density (kg/m^3); g = surface gravity (m/s^2);
# aB = Bond albedo (unitless); aV = visual geometric albedo (unitless); H = absolute visual magnitude; tr = topographic range (m);
# kI = moment of inertia coefficient (I/MR^2, unitless); a = semimajor axis (m); sdyr = sidereal year (orbital period, s);
# yr = tropical year (time for repetition of seasons, s); e = orbital eccentricity (unitless); srp = sidereal rotation period (s);
# day = length of day (s); eps = axial tilt (degrees - NOT SI!); P = surface air pressure (Pa); rhoa = surface air density (kg/m^3);
# T = average surface temperature (K); mua = mean molecular weight of atmospheric air (g/mol - NOT SI!)
# Atmospheric data omitted for moons with no substantial atmosphere
Earth = { GM = atod("3.986004418e14"), M = atod("5.97219e24"), R = atod("6.37100e6"), Re = atod("6378137.0"), Rp = atod(" 6356752.314"), rho = atod("5513.4"), rhou = atod("4020."), g = atod("9.80"), aB = atod("0.306"), aV = atod("0.367"), H = atod("-3.86"), tr = atod("2.0e4"), kI = atod("0.3308"), a = atod("1.4960e11"), sdyr = atod("31558149.54"), e = atod("0.0167"), srp = atod("86164.0905"), yr = atod("31556925.1"), day = atod("86400.002"), eps = atod("23.45"), P = atod("1.014e5"), rhoa = atod("1.217"), T = atod("288."), mua = atod("28.97") }
Moon = { GM = atod("4.902801e12"), M = atod("7.34581e22"), R = atod("1.7375e6"), Re = atod("1.7381e6"), Rp = atod("1.7360e6"), rho = atod("3344."), rhou = atod("3340."), g = atod("1.62"), aB = atod("0.11"), aV = atod("0.12"), H = atod("0.21"), tr = atod("1.6e4"), kI = atod("0.394"), a = atod("3.844e8"), sdyr = atod("2.36060e6"), e = atod("0.0549"), srp = atod("2.36062e6"), day = atod("2.551e6"), eps = atod("6.68") }
Mars = { GM = atod("4.28283762120e13"), M = atod("6.41693e23"), R = atod("3.3895e6"), Re = atod("3.3962e6"), Rp = atod("3.3762e6"), rho = atod("3934.0"), rhou = atod("3710."), g = atod("3.70"), aB = atod("0.250"), aV = atod("0.150"), H = atod("-1.52"), tr = atod("3.0e4"), kI = atod("0.366"), a = atod("2.2792e11"), sdyr = atod("5.935505e7"), e = atod("0.0935"), srp = atod("88642.663"), yr = atod("59354430."), day = atod("88775.244"), sol = atod("88775.244"), eps = atod("25.19"), P = atod("636."), rhoa = atod("0.020"), T = atod("210."), mua = atod("43.34") }
Phobos = { GM = atod("711200."), M = atod("1.0656e16"), R = atod("1.11e4"), rho = atod("1872."), aV = atod("0.071"), H = atod("11.8"), a = atod("9.378e6"), sdyr = atod("27553.8"), e = atod("0.0151"), srp = atod("27553.8") }
Deimos = { GM = atod("98500."), M = atod("1.476e15"), R = atod("6.2e3"), rho = atod("1471."), aV = atod("0.068"), H = atod("12.89"), a = atod("2.3459e7"), sdyr = atod("109075."), e = atod("0.0005"), srp = atod("109075.") }
define solsys(0,1) {
if ($ARGC == 0) {
printf("\n")
printf("solsys returns descriptions of solar system planet structures\n")
printf("solsys(\"fieldname\") returns description of the input field\n")
printf(" e.g. solsys(\"M\") returns \"Mass (in kilograms)\"\n")
printf("solsys(\"structname\") prints a full description of the specified structure\n")
printf(" e.g. solsys(\"Mars\") explains every field in the Mars structure\n")
printf("Input must be a string\n")
printf("Values in SI/mks units, mostly from the JPL SSD values at\n")
printf(" at http://ssd.jpl.nasa.gov/?constants and NASA planetary fact sheets\n")
printf(" at http://nssdc.gsfc.nasa.gov/planetary/planetfact.html\n\n")
printf("S.Marshall 10-03-2009\n\n")
return(null)
}
# Inputs asking about parameters:
if ($1 == "a") {
return("Semimajor axis of orbit (in meters)")
}
if ($1 == "aB") {
return("Bond albedo (unitless)")
}
if ($1 == "aV") {
return("Visual geometric albedo (unitless)")
}
if ($1 == "day") {
return("Mean length of day (in seconds)")
}
if ($1 == "e") {
return("Eccentricity of orbit (unitless)")
}
if ($1 == "eps") {
return("Rotation axial tilt (in degrees - NOT SI)")
}
if ($1 == "g") {
return("Acceleration due to gravity at surface (in m/s^2)")
}
if ($1 == "GM") {
return("Gravitational parameter, G*M (in m^3/s^2)")
}
if ($1 == "H") {
return("Absolute visual magnitude (of a planet, moon, asteroid, or comet)")
}
if ($1 == "kI") {
return("Moment of inertia coefficient (I/(M*R^2))")
}
if ($1 == "L") {
return("Luminosity (of a star, in Watts)")
}
if ($1 == "M") {
return("Mass (in kilograms)")
}
if ($1 == "mua") {
return("Mean molecular weight/mass of atmospheric air (in grams per mole - NOT SI)")
}
if ($1 == "MV") {
return("Absolute visual magnitude (of a star)")
}
if ($1 == "P") {
return("Atmospheric pressure at surface (in Pascals)")
}
if ($1 == "R") {
return("Volumetric mean radius (in meters)")
}
if ($1 == "Re") {
return("Equatorial radius (for near-spherical objects), in meters)")
}
if ($1 == "Rp") {
return("Polar radius (for near-spherical objects), in meters)")
}
if ($1 == "rho") {
return("Mean mass density (in kilograms per cubic meter)")
}
if ($1 == "rhoa") {
return("Mass density of air at surface (in kilograms per cubic meter)")
}
if ($1 == "rhou") {
return("Uncompressed mass density (in kilograms per cubic meter)")
}
if ($1 == "sdyr") {
return("Sidereal year / orbital period (in seconds)")
}
if ($1 == "sol") {
return("Sol / mean length of Martian day (in seconds)")
}
if ($1 == "srp") {
return("Sidereal day / rotation period (in seconds;\n for the Sun, this is the rotation period at 16 degrees latitude)")
}
if ($1 == "T") {
return("Average/effective surface temperature (in Kelvin)")
}
if ($1 == "tr") {
return("Topographic range (in meters)")
}
if ($1 == "yr") {
return("Tropical year (time for repetition of seasons, in seconds)")
}
# Inputs asking about the structures:
if ($1 == "Sun") {
global(Sun)
printf("\n Sun\n\n")
printf(" GM = %.11e m^3/s^2 Gravitational parameter\n", Sun.GM)
printf(" M = %.4e kg Mass\n", Sun.M)
printf(" R = %.2e m Volumetric mean radius\n", Sun.R)
printf(" rho = %d kg/m^3 Mean mass density\n", Sun.rho)
printf(" kI = %.3f Moment of inertia coefficient (I/MR^2)\n", Sun.kI)
printf(" MV = %.2f Absolute visual magnitude\n", Sun.MV)
printf(" L = %.3e W Luminosity\n", Sun.L)
printf(" srp = %.4e s Sidereal rotation period (at 16 degrees latitude)\n", Sun.srp)
printf(" T = %d K Effective surface temperature\n\n", Sun.T)
}
if ($1 == "Earth") {
global(Earth)
printf("\n Earth\n\n")
printf(" GM = %.9e m^3/s^2 Gravitational parameter\n", Earth.GM)
printf(" M = %.4e kg Mass\n", Earth.M)
printf(" R = %.5e m Volumetric mean radius\n", Earth.R)
printf(" Re = %.5e m Equatorial radius\n", Earth.Re)
printf(" Rp = %.4e m Polar radius\n", Earth.Rp)
printf(" rho = %.1f kg/m^3 Mean mass density\n", Earth.rho)
printf(" rhou = %d kg/m^3 Uncompressed mass density\n", Earth.rhou)
printf(" g = %.2f m/s^2 Surface gravity\n", Earth.g)
printf(" aB = %.3f Bond albedo\n", Earth.aB)
printf(" aV = %.3f Visual geometric albedo\n", Earth.aV)
printf(" H = %.2f Absolute visual magnitude\n", Earth.H)
printf(" tr = %d m Topographic range\n", Earth.tr)
printf(" kI = %.4f Moment of inertia coefficient (I/MR^2)\n", Earth.kI)
printf(" a = %.4e m Semimajor axis of orbit\n", Earth.a)
printf(" sdyr = %.2f s Sidereal year (orbital period)\n", Earth.sdyr)
printf(" e = %.4f Orbital eccentricity\n", Earth.e)
printf(" srp = %.4f s Sidereal rotation period\n", Earth.srp)
printf(" yr = %.1f s Tropical year (season repetition period)\n", Earth.yr)
printf(" day = %.3f s Length of day\n", Earth.day)
printf(" eps = %.2f degrees Rotation axial tilt\n", Earth.eps)
printf(" P = %d Pa Atmospheric pressure at surface\n", Earth.P)
printf(" rhoa = %.3f kg/m^3 Density of air at surface\n", Earth.rhoa)
printf(" T = %d K Average surface temperature\n", Earth.T)
printf(" mua = %.2f g/mol Mean molecular weight of atmospheric air\n\n", Earth.mua)
}
if ($1 == "Moon") {
global(Moon)
printf("\n Earth's Moon\n\n")
printf(" GM = %.6e m^3/s^2 Gravitational parameter\n", Moon.GM)
printf(" M = %.4e kg Mass\n", Moon.M)
printf(" R = %.4e m Volumetric mean radius\n", Moon.R)
printf(" Re = %.4e m Equatorial radius\n", Moon.Re)
printf(" Rp = %.4e m Polar radius\n", Moon.Rp)
printf(" rho = %d kg/m^3 Mean mass density\n", Moon.rho)
printf(" rhou = %d kg/m^3 Uncompressed mass density\n", Moon.rhou)
printf(" g = %.2f m/s^2 Surface gravity\n", Moon.g)
printf(" aB = %.2f Bond albedo\n", Moon.aB)
printf(" aV = %.2f Visual geometric albedo\n", Moon.aV)
printf(" H = %.2f Absolute visual magnitude\n", Moon.H)
printf(" tr = %d m Topographic range\n", Moon.tr)
printf(" kI = %.3f Moment of inertia coefficient (I/MR^2)\n", Moon.kI)
printf(" a = %.3e m Semimajor axis of orbit\n", Moon.a)
printf(" sdyr = %.5e s Sidereal orbital period\n", Moon.sdyr)
printf(" e = %.4f Orbital eccentricity\n", Moon.e)
printf(" srp = %.5e s Sidereal rotation period\n", Moon.srp)
printf(" day = %.3e s Synodic period\n", Moon.day)
printf(" eps = %.2f degrees Rotation axial tilt\n\n", Moon.eps)
}
if ($1 == "Mars") {
global(Mars)
printf("\n Mars\n\n")
printf(" GM = %.9e m^3/s^2 Gravitational parameter\n", Mars.GM)
# Displaying nine digits after decimal, since I doubt GM is better known for Mars than for Earth
printf(" M = %.4e kg Mass\n", Mars.M)
printf(" R = %.4e m Volumetric mean radius\n", Mars.R)
printf(" Re = %.4e m Equatorial radius\n", Mars.Re)
printf(" Rp = %.4e m Polar radius\n", Mars.Rp)
printf(" rho = %d kg/m^3 Mean mass density\n", Mars.rho)
printf(" rhou = %d kg/m^3 Uncompressed mass density\n", Mars.rhou)
printf(" g = %.2f m/s^2 Surface gravity\n", Mars.g)
printf(" aB = %.3f Bond albedo\n", Mars.aB)
printf(" aV = %.3f Visual geometric albedo\n", Mars.aV)
printf(" H = %.2f Absolute visual magnitude\n", Mars.H)
printf(" tr = %d m Topographic range\n", Mars.tr)
printf(" kI = %.3f Moment of inertia coefficient (I/MR^2)\n", Mars.kI)
printf(" a = %.4e m Semimajor axis of orbit\n", Mars.a)
printf(" sdyr = %.6e s Sidereal year (orbital period)\n", Mars.sdyr)
printf(" e = %.4f Orbital eccentricity\n", Mars.e)
printf(" srp = %.3f s Sidereal rotation period\n", Mars.srp)
printf(" yr = %.6e s Tropical year (orbital period)\n", Mars.yr)
printf(" day = %.3f s Length of day (sol)\n", Mars.day)
printf(" sol = %.3f s Length of day (sol)\n", Mars.sol)
printf(" eps = %.2f degrees Rotation axial tilt\n", Mars.eps)
printf(" P = %d Pa Atmospheric pressure at surface\n", Mars.P)
printf(" rhoa = %.3f kg/m^3 Density of air at surface\n", Mars.rhoa)
printf(" T = %d K Average surface temperature\n", Mars.T)
printf(" mua = %.2f g/mol Mean molecular weight of atmospheric air\n\n", Mars.mua)
}
if ($1 == "Phobos") {
global(Phobos)
printf("\n Phobos\n\n")
printf(" GM = %d m^3/s^2 Gravitational parameter\n", Phobos.GM)
printf(" M = %.3e kg Mass\n", Phobos.M)
printf(" R = %d m Volumetric mean radius\n", Phobos.R)
printf(" rho = %d kg/m^3 Mean mass density\n", Phobos.rho)
printf(" aV = %.2f Visual geometric albedo\n", Phobos.aV)
printf(" H = %.1f Absolute visual magnitude\n", Phobos.H)
printf(" a = %.3e m Semimajor axis of orbit\n", Phobos.a)
printf(" sdyr = %.d s Sidereal orbital period\n", round(Phobos.sdyr))
printf(" e = %.4f Orbital eccentricity\n", Phobos.e)
printf(" srp = %.d s Sidereal rotation period\n\n", round(Phobos.srp))
}
if ($1 == "Deimos") {
global(Deimos)
printf("\n Deimos\n\n")
printf(" GM = %d m^3/s^2 Gravitational parameter\n", Deimos.GM)
printf(" M = %.2e kg Mass\n", Deimos.M)
printf(" R = %d m Volumetric mean radius\n", Deimos.R)
printf(" rho = %d kg/m^3 Mean mass density\n", Deimos.rho)
printf(" aV = %.3f Visual geometric albedo\n", Deimos.aV)
printf(" H = %.2f Absolute visual magnitude\n", Deimos.H)
printf(" a = %.4e m Semimajor axis of orbit\n", Deimos.a)
printf(" sdyr = %d s Sidereal orbital period\n", round(Deimos.sdyr))
printf(" e = %.4f Orbital eccentricity\n", Deimos.e)
printf(" srp = %d s Sidereal rotation period\n\n", round(Deimos.srp))
}
return(null)
}
# Unit conversion structure
# The values here are the ratio of the non-SI unit to the corresponding SI unit.
# For instance, un.ft = 0.3048 = (one foot)/(one meter), so (one foot) = un.ft*(one meter) = 0.3048 m
# Field names, units, and corresponding SI units: in = inch (m), ft = foot (m), mi = mile (m),
# ly = light-year (m), pc = parsec (m), oz = ounce mass (kg), lb = pound mass (kg),
# day = 24-hour (exactly) day (s), Jyr = Julian year, floz = fluid ounce (m^3), L = liter (m^3),
# gal = US gallon (m^3), mph = mile per hour (m/s), ozf = ounce force (N), lbf = pound force (N),
# cal = thermochemical calorie (J), tTNT = TNT equivalent tonne (J), hp = electric horsepower (W),
# mbar = millibar (Pa), torr = torr (Pa), psi = pound per square inch (Pa), bar = bar (Pa),
# atm = standard atmosphere (Pa), deg = degree (rad), arcmin = arcminute (rad), arcsec = arcsecond (rad)
un = { in = atod("0.0254"), ft = atod("0.3048"), mi = atod("1609.344"), AU = atod("149597870691."), ly = atod("9460730472580800."), pc = atod("30856775813057292."), oz = atod("0.028349523125"), lb = atod("0.45359237"), day = double(86400), Jyr = atod("3.15576e7"), floz = atod("2.95735295625e-5"), L = atod("0.001"), gal = atod("0.003785411784"), mph = atod("0.44704"), ozf = atod("4.4482216152605")/16, lbf = atod("4.4482216152605"), cal = atod("4.184"), tTNT = atod("4.184e9"), hp = double(746), mbar = double(100), torr = double(101325)/760, psi = atod("6894.75729316836"), bar = double(100000), atm = double(101325), deg = con.pi/180, arcmin = con.pi/10800, arcsec = con.pi/648000 }
# Values for the following were derived from other units' values:
# mi (5280 ft)
# pc (AU/arcsec, which uses the small-angle approximation)
# oz (1/16 lb)
# floz (1/128 gal)
# gal (231 in^3)
# mph (1 mile)/(3600 s)
# ozf (1/16 lbf)
# lbf (pound-mass times g)
# torr (1/760 of a standard atmosphere; equivalent to a millimeter of mercury)
# psi (1 lbf divided by 1 in^2)
# Varying definitions for: mile, pound, ounce, gallon, calorie, horsepower
# Units to consider for potential use: Nm (nautical mile), acre, Btu, Gauss
# Most values from http://www.nist.gov/pml/wmd/metric/upload/SP1038.pdf (via http://www.nist.gov/pml/wmd/metric/metric-pubs.cfm)
# Additional sources:
# http://ssd.jpl.nasa.gov/?constants (for AU)
# http://www.iau.org/public/measuring/ (for Julian year and light-year)
define unithelp(0) {
global(un)
if ($ARGC == 0) {
printf("\nunithelp() describes all unit conversion factors in structure un\n")
printf("S.Marshall 11-30-2010\n\n")
printf(" Most of these values are from\n")
printf(" http://www.nist.gov/pml/wmd/metric/upload/SP1038.pdf\n")
printf(" via http://www.nist.gov/pml/wmd/metric/metric-pubs.cfm\n")
printf(" Additional sources: http://ssd.jpl.nasa.gov/?constants\n")
printf(" and http://www.iau.org/public/measuring/\n\n")
printf(" Note that definitions vary for mile, pound, ounce, gallon,\n")
printf(" calorie, and horsepower. Those used here are the most common.\n\n")
printf(" The values here are the ratio of the non-SI unit to the\n")
printf(" corresponding SI unit. For instance,\n")
printf(" un.ft = 0.3048 = (one foot)/(one meter), so\n")
printf(" (one foot) = (value of un.ft)*(one meter) = 0.3048 m\n\n")
printf(" in = %.4f m Inch\n", un.in)
printf(" ft = %.4f m Foot (12 inches)\n", un.ft)
printf(" mi = %.3f m Mile (5280 feet)\n", un.mi)
printf(" AU = %.11e m Astronomical unit\n", un.AU)
printf(" ly = %.13e m Light-year (c*Jyr)\n", un.ly)
printf(" pc = %.10e m Parsec\n\n", un.pc)
printf(" oz = %.12f kg Ounce mass (avoirdupois, 1/16 lb)\n", un.oz)
printf(" lb = %.8f kg Pound mass (avoirdupois)\n\n", un.lb)
printf(" day = %d s Day (24 hours)\n", un.day)
printf(" Jyr = %.5e s Julian year (365.25 days)\n\n", un.Jyr)
printf(" floz = %.11e m^3 Fluid ounce (1/128 gal)\n", un.floz)
printf(" L = %.3f m^3 Liter\n", un.L)
printf(" gal = %.12f m^3 US gallon (231 cubic inches)\n\n", un.gal)
printf(" mph = %.5f m/s Mile per hour\n\n", un.mph)
printf(" ozf = %.15f N Ounce force\n", un.ozf)
printf(" lbf = %.13f N Pound force\n\n", un.lbf)
printf(" cal = %.3f J Calorie (thermochemical)\n", un.cal)
printf(" tTNT = %.3e J TNT equivalent tonne\n\n", un.tTNT)
printf(" hp = %d W Horsepower (electric)\n\n", un.hp)
printf(" mbar = %d Pa Millibar\n", un.mbar)
printf(" torr = %.12f Pa Torr (1/760 atm)\n", un.torr)
printf(" psi = %.11f Pa Pound per square inch\n", un.psi)
printf(" bar = %d Pa Bar\n", un.bar)
printf(" atm = %d Pa Standard atmosphere\n\n", un.atm)
printf(" deg = %.16f rad Degree (pi/180 radians)\n", un.deg)
printf(" arcmin = %.15e rad Arcminute (1/60 degree)\n", un.arcmin)
printf(" arcsec = %.15e rad Arcsecond (1/60 arcminute)\n\n", un.arcsec)
printf(" All except AU and pc are exact (to double precision)\n\n")
}
return(null)
}