how does the blue moon happen

A blue moon happens when there are two full moons in a single calendar month. This occurs because the lunar cycle is about 29.5 days, slightly shorter than the average month, allowing for a second full moon to appear if the first one happens early in the month. This phenomenon happens roughly every 2 to 3 years. There is also a type of blue moon called a seasonal blue moon, which occurs when there are four full moons in a single season instead of the usual three. Despite the name, the moon itself does not actually turn blue in this event; the term is just used to describe the timing of the moons. Occasionally, the moon can appear blue due to atmospheric conditions like smoke or dust particles that scatter red light, but this is a separate and rare phenomenon from the calendar-based blue moon definition.