I think this has been done before and I checked Primo Nation's Duplicate Thread, but I don't know where I can put my theory, so I hope its ok if I make my own thread.
In the Siege of the North, Zuko said "You rise with the moon (to Katara). I rise with the sun." Waterbenders get their power from the moon and firebenders get their power from the Sun. Here's the site where I came up with my theory: http://www.skyviewzone.com/sunsign.htm
Fire: Sun, Mars, Jupiter
Earth: Venus, Mercury, Saturn
Air: Mercury, Venus, Uranus
Water: Moon, Pluto, Neptune
I know some elements belong to??the same??planets, but I noticed Water belongs to the moon and Fire belongs to the Sun.??Is it possible that benders get their??powers from the planets? What do you think???