Blue Moon in San Ignacio

They also use this expression to designate something special, rare or strange that happens very punctual. It is very rare that a month has two full moon. Most months are between 30 and 31 days and the full moon is every 29 days, so it is possible that in a month two are adapted, but it is not normal.

However, it was really a time when the moon was blue. In 1883 the Krakatua volcano in Indonesia exploded. At 660 km they heard a drum like a cannon and the ashes reached the limit of the atmosphere.

Some of the particles of these ashes had a micron of diameter. The particles of this measure disperse the red light leaving the light of other colors. The white light emitted by the Moon became blue as it crossed the clouds of ashes and sometimes also green. That is why they saw the blue or green moon. The eruption also affected the Sun and at that time they could sometimes see a purple sun.