What Is A Lunar Eclipse?

    Published: 06-16-2009
    Views: 15,179
    Science expert Emerald Robinson explains what a lunar eclipse is and how it happens.

    Emerald Robinson: In this video we're going to take a closer look at an astronomical event called a Lunar Eclipse. To begin our investigation it's important to understand the natural phases of the moon as it revolves around the earth. These moon phases occur over the course of a month and are due to the moon's relative location to the sun with respect to earth.

    This monthly cycle is important as a Lunar Eclipse can only occur during a full moon when it is opposite the earth from the sun and fully eliminated. On rare occasions the full moon lines up precisely on the ecliptic plane, the plan on which the earth rotates around the sun. When this happens, the earth blocks sun or all of the sun's light and casts a shadow on the moon which we see as a Lunar Eclipse.

    During a Lunar Eclipse the earth shadow has two distinct parts. The Umbra is the inner cone-shaped part of the shadow is the part in which all the light has been blocked. The Penumbra is the outer part of the earth shadow, where sunlight is only partially blocked.

    Scientists recognize three types of lunar eclipses; Penumbral, Partial and Total. A Penumbral Eclipse occurs when only the Penumbral shadow is hitting the moon. A Penumbral Eclipse is very hard to see because of all the parts of the moon are still receiving some light from the sun.

    A Partial Lunar Eclipse happens when a portion of the moon enters earth's Umbra. While the rest of the moon remains in the thin light of the Penumbra. In a Total Lunar Eclipse the moon is entirely in the earth's Umbra, casting a shadow across full visible surface. But even in a total eclipse the moon remains faintly illuminated by indirect sunlight refracted through the earth's atmosphere giving the moon a thin red glow.

    Partial Lunar Eclipses occur at least twice a year, but Total Lunar Eclipses are less common. If you're lucky enough to see one be sure to get out your camera as a Lunar Eclipse provides an opportunity for some amazing photographs.