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Lunar eclipse

when the Moon passes directly behind the Earth

What is a Lunar Eclipse?Edit

A lunar eclipse occurs when the moon passes through the Earth shadow.

Lunar” is the word we use to describe things that have to do with the moon. And an eclipse is when one objects blocks, or gets in the way of, another.

So let’s use those two ideas to figure out what happens up there in the sky to make a lunar eclipse take place.

If you’ve ever noticed that you can see the moon in different parts of the sky at different times, that’s because the moon orbits, or goes around, the Earth. It makes a full trip around us once a month.

And at the same time that the moon is orbiting the Earth, the Earth is also going orbiting around the sun. So at different times, the sun, moon and Earth are in different positions.

And every once in a while, the Earth happens to get right smack-dab in between the Sun and the moon.

And they end up in a straight line. When they all line up this way, the Earth blocks some of the sun’s light and casts a big shadow on the moon.

That, my fellow sky-watchers, is a lunar eclipse. But the shadow that the Earth casts on the moon isn’t black. It’s not even really that dark!

Instead, during a lunar eclipse, the moon can look red! That’s because when sunlight shines from behind the Earth, it travels through our atmosphere. And that light bends when it shines around the Earth. Those bent rays of sunlight then create a red color on the moon.

Lunar eclipses are famous for turning the moon red, but they can be other colors, too like yellow, orange, or brown.

What color you see depends partly on where you are when you’re watching it. And not everyone on Earth can see the eclipse — only people who happen to be on the side of the Earth that’s facing the moon when it happens can see it. Generally, that’s the side where it’s nighttime.


 
A lunar eclipse occurs in two regions, an outer penumbral shadow where the sunlight is dimmed, and an inner umbral shadow, where much dimmer sunlight only exists by refraction through the Earth's atmosphere, leaving a red color.
This can be seen in different exposures of a partial lunar eclipse, for example here with exposures of 1/80, 2/5, and 2 seconds.
 
A solar eclipse occurs in the day-time at new moon, when the Moon is between the Earth and the Sun
A lunar eclipse occurs when the Earth passes between the Sun and the Moon

A lunar eclipse is an astronomical phenomenon. It happens when the moon passes through the shadow of the Earth which can only occur during a full moon. Lunar eclipses happen about twice a year, unlike total solar eclipses that are sometimes more than a year apart. They can be seen from a much larger portion of the Earth compared to solar eclipses. Lunar eclipses can last for a few hours, but total solar eclipses last only a few minutes.

During a lunar eclipse, the Moon looks red-brown. It may be thought that the Moon is completely black because of the Earth's shadow, but no. The reddish-brown color is because some of the Sun's light bends through the Earth's atmosphere and shines on the Moon. Refraction is greater for red light rays than for others, so red is what strikes the Moon.

Like solar eclipses, there are different types of lunar eclipses. There are total eclipses, where the moon passes completely through Earth's shadow and all of the moon appears reddish-brown. A partial eclipse occurs when only part of the moon passes through Earth's shadow and so only part of the moon appears reddish-brown.

Lunar eclipses are safe to view with just your eyes and also with telescopes.