[RadioKid]

Though it is not sensitive subject (to enjoy the discussion), I would like to point out 陽 is basically used with 陰 like as 陰陽(minus and plus side of things). 陰陽 also means shadow side and lighten side. This leads 陽 for sun-light.

As for the comparison of "陽が落ちる" and "日が落ちる", it might be caused by the Japanese IME(Input Method Editor). As most Japanese does not care of the difference of 陽 and 日, "ひがおちる" would be converted to "日が落ちる" by default. Considering this default conversion, unexpectedly many people choice "陽が落ちる" consciously.

>IMHO, 陽 simply means 太陽.
By the way, what do youmean by IMHO?