There are blue moons, an extra unfamiliar moon in one month, and there is a blue hunter moon – which is quite rare.

In most years, we only see one moon a month. In the case of the blue moon, one month passes by two full moons, bringing the total to thirteen years. The term traces its origins from Maine Farmer Calendar, A guide containing meteorological and astronomical signals to help farmers keep track of the season.

The book states that a blue moon is actually the third moon in a season with four full moons, instead of three in each quarter. Provides a correction in estimating season length and hence planting schedules.

Unfortunately, a misunderstanding in an article published in March 1946 simplifies the rule, incorrectly, as the second moon of the month.

A blue hunter moon for the whole world

Blue moons occur at least once every two or three years. However, astronomers are following the 19-year cycle of the Moon’s movement around the Earth. Known as the Metonic cycle, this period predicts the frequency of the moon’s position on each day of the year. The Greek and Hebrew calendars follow the cycle in calculating the date of Easter, as the Babylonians followed a similar 19-year cycle since the sixth century BC.

Now that a blue moon is expected to appear on Halloween, October 31, the Metonic cycle suggests that it should happen once every nineteen years. This full moon that will happen to Halloween is also called the Hunter’s Moon – the moonlight in autumn that guides hunters in finding stocks of food to keep them going throughout the winter.

Related: This year’s harvest moon is due to rise in October

Unfortunately, the Metonic cycle is not completely synchronized with the Gregorian calendar we use today. Strictly speaking, the Metonic cycle stops by 1 hour 27 minutes 33 seconds – requiring a once-leap day in all 219 years. In comparison, the Gregorian calendar requires a correction in the form of a leap day every four years.

Although the hunter’s blue moon was visible in some parts of the Earth nineteen years ago, 2001, the last full moon of this type appeared in most parts of the world was actually in 1944 – 76 years old, or four Metonic cycles before. Unfortunately, regions of the South Pacific such as parts of Australia and New Zealand will not be part of this event. However, they will have their blue moon after another 19 years – in 2039!

Actual blue moon

It is important to note that the term “blue moon” simply refers to the second full moon in the month, and it is not necessarily the color of the moon that we will see. However, with the right weather conditions – mostly particles in the air – they made the moon appear blue several times throughout recorded history.

The eruption of the Krakatoa volcano in 1883 was one of the earliest and most significant events leading to the creation of a literally blue moon. The giant volcano erupted in what was among the most deadly and destructive events in history. The entire island of Krakatoa, as well as its neighboring islands, was wiped off the face of the earth – leaving a large caldera in its place. Aside from the shock waves that were felt all over the world, the explosion threw materials into the atmosphere Around a blue moon For nearly two years after the event.

Related: Krakatoa volcano erupting with three others in Indonesia; Local residents are starting to sleep because they are still fighting against Coronavirus