In fact, if you watched the eclipse from the surface of the Moon, you'd see the Sun set behind the entire Earth, bathing you in a warm red glow. Once it's entirely within the umbra, the Moon appears a dim red due to sunlight scattered through the Earth's atmosphere. About twice a year, this puts the Moon in just the right position to pass through the Earth's shadow, causing a lunar eclipse.Īs the Moon passes into the central part of the Earth's shadow, called the umbra, it darkens dramatically. Throughout the year, the Moon's orbital tilt remains fixed with respect to the stars, meaning that it changes with respect to the Sun.

But if that's the case, why do eclipses happen at all? The reason is that the Moon's orbit around the Earth is tilted relative to the Earth's orbit around the Sun. So why don't eclipses happen twice a month?

Credit: NASA/Bill IngallsĪ lunar eclipse occurs when the Moon passes through the Earth's shadow, just as a solar eclipse occurs when part of the Earth passes through the Moon's shadow. From there, an observer during an eclipse would see all Earth's sunrises and sunsets at once.Ī composite of seven images shows the full Moon at perigee, or supermoon, during a total lunar eclipse on Sunday, Sept. This is because the only remaining sunlight reaching the Moon at that point is from around the edges of the Earth, as seen from the Moon's surface.

A partial lunar eclipse happens when only part of Earth's shadow covers the Moon.ĭuring some stages of a lunar eclipse, the Moon can appear reddish.

A total lunar eclipse occurs when the Moon and Sun are on opposite sides of Earth.

What is a Lunar Eclipse?ĭuring a lunar eclipse, Earth comes between the Sun and the Moon, blocking the sunlight falling on the Moon. The cycle repeats once a month (every 29.5 days). These eight phases are, in order, new Moon, waxing crescent, first quarter, waxing gibbous, full Moon, waning gibbous, third quarter and waning crescent. The rest of the month we see parts of the daytime side of the Moon, or phases. When sunlight reflects off the near side, we call it a full Moon. When sunlight hits off the Moon's far side - the side we can't see without from Earth the aid of a spacecraft - it is called a new Moon.

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