A total lunar eclipse occurs when the Earth passes directly between the Sun and the Moon, casting a complete shadow (umbra) on the Moon's surface.
Here's a more detailed explanation:
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Alignment: For a total lunar eclipse to happen, the Sun, Earth, and Moon must be almost perfectly aligned. This alignment is called syzygy.
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Earth's Shadow: As the Earth moves between the Sun and Moon, it casts two shadows:
- Umbra: The dark, central part of the shadow where sunlight is completely blocked.
- Penumbra: The lighter, outer part of the shadow where sunlight is partially blocked. A penumbral lunar eclipse occurs when the Moon passes only through the penumbra, resulting in a subtle dimming of the lunar surface that's often hard to notice.
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Entering the Umbra: During a total lunar eclipse, the Moon first passes through the penumbra, resulting in a slight darkening. As it moves further, it enters the umbra.
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Totality: The "total" phase of the eclipse begins when the entire Moon is within the umbra. During totality, the Moon typically appears reddish or orange. This is due to a phenomenon called Rayleigh scattering, where the Earth's atmosphere scatters sunlight, with redder wavelengths being refracted towards the Moon. The amount of red color depends on the amount of dust and clouds in Earth's atmosphere.
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Duration: The duration of a total lunar eclipse can vary, depending on how centrally the Moon passes through the Earth's umbra.
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Visibility: A lunar eclipse is visible from anywhere on Earth where the Moon is above the horizon at the time of the eclipse. This makes lunar eclipses more widely visible than solar eclipses.
In summary, a total lunar eclipse is a celestial event where the Moon is completely obscured by the Earth's umbral shadow, resulting in a reddish appearance of the Moon.
