Constants

Physical and mathematical constants and units taken from SciPy.

pi, twopi, halfpi	Pi and multiples
c	speed of light in vacuum
G	Newtonian constant of gravitation
g0	Standard acceleration of gravity
degree	degree in radians
arcmin	arc minute in radians
arcsec	arc second in radians
miliarcsec	milliarcsecond in radians
minute	one minute in seconds
hour	one hour in seconds
day	one day in seconds
year	one year (365 days) in seconds
julian_year	one Julian year (365.25 days) in seconds
au	one astronomical unit in meters
light_year	one light year in meters
parsec	one parsec in meters
km	kilometers in meters
kmh	kilometers per hour in meters per second