Lunar Eclipse 101 | National Geographic

What is a Lunar Eclipse?00:00:03

A lunar eclipse occurs when the Earth blocks some or all of the sun's direct light from reaching the moon. This event only happens during a full moon, which is every 29 and a half days, but not every month due to the moon's tilted orbit relative to the Earth.

Earth's Shadows and Types of Eclipses00:00:38

When the Earth eclipses the sun, it casts two types of shadows on the moon: the larger penumbra and the smaller, darker umbra. There are three types of lunar eclipses: total, partial, and penumbral.

Total Lunar Eclipse & The Red Moon00:00:56

A total lunar eclipse happens when the sun, moon, and earth are perfectly aligned, and the moon falls within the Earth's umbral shadow. These are the most striking because the moon turns a sunset red. This happens because Earth's atmosphere scatters shorter blue wavelengths of light while refracting longer red wavelengths inward towards the moon. The brightness of the red glow depends on the amount of dust and clouds in Earth's atmosphere, with volcanic activity potentially making it darker.

Partial and Penumbral Lunar Eclipses00:01:41

A partial lunar eclipse occurs when the alignment is not perfect, and only part of the moon passes into Earth's umbra, making Earth's shadow appear dark on that section of the moon. A penumbral lunar eclipse happens when the moon passes through Earth's penumbral shadow, making the moon appear only slightly darker than normal, often unnoticed by most.

Observing Lunar Eclipses and Future Implications00:02:15

Lunar eclipses can occur up to three times a year and are safe to observe with the naked eye from anywhere on the nighttime side of Earth. Total lunar eclipses are only possible due to the specific distances of the sun and moon from Earth. Billions of years from now, the moon will have inched far enough away from Earth that it will no longer fall completely within Earth's umbral shadow, ending total lunar eclipses.