This Friday, there will be a once in a blue moon occurrence. If you step outside, you might find yourself gazing out at a brimming, full moon. Disappointingly, it won't actually be blue; the term is a misnomer. In fact, a blue moon isn't any different to any other full moon. 

In the past, a blue moon was used to mean "rare," but now the name is given to any full moon that is the second to appear in one calendar month. The lunar cycle is around 29 and a half days, and months of the year are between 28 and 31 days long. The probability of a full lunar cycle, from full moon to full moon, occurring precisely during this time window is therefore not very high.

The next blue moon, by this definition, is going to be on January 31, 2018 – around two and a half years from now. Ther ... Czytaj więcej »