User: cott Date: 2012/12/29 06:57 AM

Added: /trunk/doc/ units.py

Log: * add a python script that computes cgs->M_sun=c=G=1 units conversion factors (and their inverses) based on NIST data

File Changes:

Directory: /trunk/doc/ ======================

File [added]: units.py Delta lines: +53 -0 =================================================================== --- trunk/doc/units.py (rev 0) +++ trunk/doc/units.py 2012-12-29 12:57:38 UTC (rev 71) @@ -0,0 +1,53 @@ +# Copyright Christian D. Ott, Dec 29, 2012 +# cott@tapir.caltech.edu +# +# python script that takes fundamental constants and spits out +# conversion factors between c = G = M_Sun = 1 and cgs + +# constants from NIST table, 2010 data +# solar mass from http://asa.usno.navy.mil/SecK/2013/Astronomical_Constants_2013.pdf + +ggrav = 6.6738480e-8 #cgs +clite = 2.99792458e10 #cgs +msun = 1.9884e33 #cgs + +print "Using the following constants:" +print "G: 6.6738480e-8 cm**3 / g / s**2" +print "c: 2.99792458e10 cm / s" +print "M_sun: 1.9884e33 g" + +print " mass_gf=%22.14E" % (1.0/msun) +print " inv_mass_gf=%22.14E" % msun + +# length +length_gf = 1.0/(ggrav/clite**2 * msun) +inv_length_gf = 1.0/length_gf + +print " length_gf=%22.14E" % length_gf +print "inv_length_gf=%22.14E" % inv_length_gf + +# density +rho_gf = 1.0/msun * 1.0/length_gf**3 +inv_rho_gf = 1.0/rho_gf + +print " rho_gf=%22.14E" % rho_gf +print " inv_rho_gf=%22.14E" % inv_rho_gf + +# time +time_gf = clite * length_gf +inv_time_gf = 1.0/time_gf +print " time_gf=%22.14E" % time_gf +print " inv_time_gf=%22.14E" % inv_time_gf + +# specific internal energy erg / gram +eps_gf = 1.0/clite**2 +inv_eps_gf = clite**2 +print " eps_gf=%22.14E" % eps_gf +print " inv_eps_gf=%22.14E" % inv_eps_gf + +# pressure +press_gf = 1.0/msun * inv_time_gf**2 * inv_length_gf +inv_press_gf = 1.0/press_gf +print " press_gf=%22.14E" % press_gf +print " inv_press_gf=%22.14E" % inv_press_gf +