What Is a Lunar Eclipse?
A lunar eclipse is an astronomical event that occurs when the Moon passes directly behind Earth and into its shadow. This can only happen when the Sun, Earth, and Moon are exactly or very closely aligned, with Earth positioned in the middle. This alignment is known as syzygy and only occurs during a full moon.
Section 2: The Role of Earth's Shadow
Earth's shadow has two distinct parts: the umbra and the penumbra. The umbra is the darker, central part of the shadow where the Sun is completely blocked by Earth. The penumbra is the fainter, outer part where the Sun is only partially blocked. The type of lunar eclipse depends on which part of the shadow the Moon passes through.
Section 3: Types of Lunar Eclipses
There are three main types. A **total lunar eclipse** occurs when the entire Moon passes through Earth's umbra, often appearing reddish. A **partial lunar eclipse** happens when only part of the Moon enters the umbra. A **penumbral lunar eclipse** is when the Moon passes only through the faint penumbra, causing a subtle dimming that can be difficult to notice.
Section 4: Why Don't We Have One Every Full Moon?
A lunar eclipse doesn't happen during every full moon because the Moon's orbit around Earth is tilted by about 5 degrees relative to Earth's orbit around the Sun. Due to this tilt, the Moon usually passes above or below Earth's shadow. An eclipse only occurs when the full moon's path crosses the plane of Earth's orbit.