July ended with what is called, by some, a “blue moon” – but this does not have a simple explanation. For many it was called a “blue moon” because it infrequently happens that we have two full moons in a single month, and normally we only have one full moon each month.
July, you will recall, is one of the long months with 31 days, and months (a word derived from moon) vary in length (four months have 30 days, seven have 31), and in particular February has an extra day (29) in a Leap Year like 2016.
The problem is simple. Man’s “months” do not exactly match up with planetary movements and months. Some months therefore occasionally have two full moons instead of one and sometimes a month has no full moon at all. Some seasons (lasting three months) sometimes may also have four full moons instead of three.
However you may see a moon that actually looks “blue” occasionally if volcanic eruptions or large fires (like the current bush fires in California) leave lots of particles in the atmosphere affecting what you see. The 1883 Krakatoa eruption made the moon look blue for two years. However forest fires can sometimes make the moon seem to be coloured red.
A blue moon therefore refers to a fairly rare event when lunar cycles do not match up to our months. For more detail go to wikipedia but prepare to be confused.
Photo: Seana Lanigan