When I first heard about it a few weeks ago, I actually thought that the moon will appear blue on that night because of some extraordinary space event. My excitement was short-lived; it was crashed by the Google within a few hours.
The 'blue moon' is actually a phenomenon in which the full moon appears for the second time within a month's duration. This is because the moon usually completes an orbit around the Earth in 29.5 days, but a month is usually 30 or 31 days except for the month of February. So, full moon appears twice a month every two and a half years on average according to NASA.
A picture of the moon taken using blue filter Source: http://www.nasa.gov/vision/universe/watchtheskies/07jul_bluemoon.html |