The passage of the moon through the Earth's shadow, visible from anywhere on Earth's night side where the moon is above the horizon, unlike a solar eclipse's narrow path. During a total lunar eclipse the moon does not vanish but typically takes on a reddish hue, the so-called blood moon effect, as sunlight filtered through Earth's atmosphere falls onto the lunar surface. Lunar eclipses occur only during a full moon and are entirely safe to view with the naked eye.
Facts
PeriodicityLunar eclipses occur an average of about 2.28 times per year in the 21st century, with at least two happening every year 2 ScaleUnlike a solar eclipse's narrow path, a lunar eclipse can be seen at once from the entire night side of Earth and often lasts an hour or longer 2 First DescribedThe earliest known eclipse record comes from Babylon, documenting a lunar eclipse on 6 February 747 BC; the Greek philosopher Anaxagoras was the first to commit to writing, plainly and confidently, that the Moon is eclipsed by the Earth's shadow 3 Identification
Distinguishing AppearanceDuring totality the Moon typically turns a shade of red rather than disappearing, with the exact hue and brightness ranging on the Danjon scale from a very dark, almost invisible eclipse to a bright copper red or orange one 1 Sources
1. NASA Eclipse Web Site - Visual Appearance of Lunar Eclipses
Danjon scale sectionQuote, Danjon scale section
the exact color can vary considerably in both hue and brightness
2. Wikipedia - Lunar Eclipse
Frequency section
In the 21st century there are 228 lunar eclipses, an average of 2.28 per year, with at least two every year.
Visibility section
lunar eclipses can be observed from anywhere on the night side of Earth and often last for an hour or longer
View the Source3. NASA Eclipse Web Site - Lunar Eclipses of Historical Interest
First correct explanation sectionQuote, First correct explanation section
For he who the first, and the most plainly of any, and with the greatest assurance committed to writing how the moon is enlightened and overshadowed, was Anaxagoras
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