L E N G T H	1 angstrom (Å)	10-10 m
	1 nanometer (nm)	10-9 m
	1 micron (µm)	10-6 m
	1 centimeter (cm)	0.01 m
	1 meter (m)	100 cm
	1 kilometer (km)	1000 m = 105 cm
	Earth Radius (R)	6378 km
	Solar Radius (R)	6.96 x 108 m
	1 astronomical unit (A.U.)	1.496 x 1011 m
	1 light year (ly)	9.46 x 1015 m = 63,200 A.U.
	1 parsec (pc)	3.09 x 1016 m = 3.26 ly
	1 kiloparsec (kpc)	1000 pc
	1 megaparsec (Mpc)	1000 kpc
M A S S	1 gram (g)
	1 kilogram (kg)	1000 g
	Earth Mass (M)	5.98 x 1024 kg
	Solar Mass (M)	1.99 x 1016 m
T I M E	1 second (s)
	1 hour (h)	3600 s
	1 day (d)	86,400 s
	1 year (yr)	3.16x107 s

C O N V E R S I O N	1 inch = 2.54 centimeters (cm)
	1 foot (ft) = 0.3048 meters (m)
	1 mile = 1.609 kilometers (km)
	1 pound (lb) = 453.6 grams (g) or 0.4536 kilograms (kg) on Earth)

R O U N D E D O F F C O N S T A N T S	astronomical unit	1 A.U. = 1.5 x 108 km
	light year	1 ly = 1013 km; 6 trillion miles
	parsec	1 pc = 3.3 ly
	speed of light	c = 3 x 105 km/s
	Stefan-Boltzmann constant	[Greek Sigma] = 5.67 x 10-8 W/m2·K4
	Planck's constant	h = 6.63 x 10-34 Js
	gravitational constant	G = 6.67 x 10-34 Js
	mass of the Earth	M = 6 x 1024 kg about 6000 billion billion tons
	radius of the Earth	R = 6500 km
	mass of the Sun	M = 2 x 1030 kg
	radius of the Sun	R = 7 x 105 km
	luminosity of the Sun	L = 4 x 1026 W
	effective temperature of the Sun	T = 5800 K
	Huble constant	H0 = 65 km/s/Mpc
	mass of the electron	me = 9.11 x 10-31 kg
	mass of the proton	mp = 1.67 x 10-27 kg