This August we will have two full moons! The second one that is called “Blue Moon” falls on the last night of summer.
Blue moon is a second full moon that takes place within one month. This year it will happen in August: the first fool moon will be on August, 2 and the second and more “rare” one – on August, 31.
It is not a very common phenomenon when two full moons are observed within one month, especially when it comes to the August moon. The second full moon in the month is called “blue”, not only because it is rare and unusual but because once it really used to be blue. And not for just one night, but for years.
In 1883 the great eruption of Krakatoa volcano occured in Indonesia. Being 600 km away, people heard the explosion as a cannon shot. The explosion was equivalent to the effect of 100 megaton bomb. Dust and ashes ejected in the upper layers of the atmosphere. Then the refraction of moonlight in the smog particles from volcanic eruptions gave the moon a blue color.
“It was so weird and rare that since then people started saying “once in a blue moon” as an expression with a meaning of “almost never“ says director of the Eugenides Foundation Planetarium.
“With this meaning we also use the phrase “blue moon” to describe the appearance of two full moons within one month. However, the second full moon in the month that is called “blue” is not such a rare phenomenon that occurs every 2,7 years” adds the director.