Let's Learn About: Total lunar eclipse

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If the weather cooperates early Tuesday morning, you can witness one of nature's majestic displays, a total lunar eclipse.

A total lunar eclipse occurs at full moon when the entire moon passes through Earth's umbral, or inner shadow. Earth's shadow is made up of two cone-shaped components nestled inside the other. The penumbra, or outer shadow, is where Earth blocks part of the sun's rays from reaching the moon. The umbra, or inner shadow, is a region where Earth blocks all direct sunlight from reaching the moon. Once the moon contacts the edge of the umbral shadow, it takes about one hour to be fully immersed in the shadow and totality begins. Totality during Tuesday morning's eclipse begins at 3:08 a.m. and lasts about 75 minutes until it ends at 4:23 a.m.

An eclipse does not occur every time there is a full moon because the moon's orbit around Earth doesn't lie exactly in the ecliptic, the plane in which Earth orbits the sun. The moon's orbit is inclined by about 5 degrees with respect to it. So, in the course of a month, the moon travels above or below Earth's shadow.

During totality, the moon can take on an array of colors from red to dark brown or bright orange. The color depends on how much dust and how many clouds are present in the atmosphere. If enough particles are present, for instance after the eruption of a volcano, the moon can even appear very dark.

If you see the moon turn red, it's because the light that was hitting the moon from the sun had to go through Earth's atmosphere. The atmosphere scatters blue light more than red light so what comes out the other side is red. This reddish light bounces off the moon, comes back to Earth and enters your eyes.


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