What causes solar and lunar eclipses?

Solar and lunar eclipses are caused by the alignment of the Earth, Moon, and Sun.

A solar eclipse occurs when the Moon moves between the Earth and the Sun, blocking the Sun's light and casting a shadow on Earth. This can only happen during a new moon phase, when the Moon is directly between the Earth and the Sun. There are three types of solar eclipses: total, partial, and annular. In a total solar eclipse, the Moon completely covers the Sun. During a partial solar eclipse, the Moon only partially covers the Sun. An annular solar eclipse happens when the Moon is farthest from Earth. It doesn't block the entire view of the Sun, creating a ring of sunlight around the Moon.

On the other hand, a lunar eclipse happens when the Earth moves between the Sun and the Moon, blocking the Sun's light from reaching the Moon. This can only occur during a full moon phase, when the Earth is directly between the Sun and the Moon. There are also three types of lunar eclipses: total, partial, and penumbral. In a total lunar eclipse, the Earth's shadow completely covers the Moon. During a partial lunar eclipse, only a portion of the Moon enters Earth's shadow. In a penumbral lunar eclipse, the Moon passes through an outer part of Earth's shadow, causing a subtle darkening of the Moon's surface.

The occurrence of solar and lunar eclipses is not random but is governed by the orbits of the Earth and Moon. The tilt of the Moon's orbit means that it usually passes above or below the Earth's shadow, so lunar eclipses do not occur every month. Similarly, the Moon's shadow usually misses the Earth, so solar eclipses are also not a monthly event. The precise alignment required for an eclipse to occur is known as syzygy, a term derived from the Greek word for "yoked together".