It's the second full moon of August, 2012 - the last one was in March 2010. The next one won't be until July 2015. This is a good time to explain what a blue moon really is, since most people misunderstand it to mean the second full moon in a month. Technically, it's the the third full moon in a season with four full moons. Sky & Telescope thoroughly and clearly explains the science behind this lunar occurrence. Today it is commonly thought of as the second full moon in one month. So, it's the perfect time to listen to Ella Fitzgerald softly singing Rodgers and Hart's classic "Blue Moon," one of their most plaintive ballads.