Here's why:
* Lunar eclipses require specific alignment: A lunar eclipse happens when the Earth passes directly between the Sun and the Moon, casting its shadow on the Moon. This alignment doesn't happen every year, let alone every 4 years.
* Frequency of lunar eclipses: Lunar eclipses occur a few times a year, but not every time the Moon is full. The exact frequency varies depending on the orbital positions of the Earth, Moon, and Sun.
Here's a more accurate explanation:
* Total lunar eclipses: Occur approximately every 2.5 years.
* Partial lunar eclipses: Occur more frequently, several times a year.
So, while lunar eclipses aren't uncommon, they don't occur on a strict 4-year cycle.
