Why The Moon Turns Red During A Total Lunar Eclipse

– A blood moon lunar eclipse
wasn’t always something to look forward to. When the moon turned red thousands of years ago, the ancient Mayans and Mesopotamians feared
that something monstrous and evil was eating the moon. They would shout at the night sky to try and fend off the ravenous beasts and since the average lunar eclipse lasts around 100 minutes, and the moon returns to normal afterward, they
were probably convinced that their whooping and
howling actually worked. We know now that the moon
doesn’t need our protection, but why does it turn
red in the first place? (peaceful music) Whenever you look up at a full moon, you’re seeing sunlight that’s reflected off the lunar surface, so if something were
to block that sunlight say, the earth, then in theory, the moon should disappear from view but during a total lunar eclipse when the moon passes
through the earth’s shadow, we get a red moon, not a vanishing one. So what’s going on? To figure it out, let’s take a quick trip to the lunar surface. This is a NASA simulation
of what the earth looks like during a total lunar eclipse. Notice the red ring around our planet. Everywhere you see that
ring is either a sunrise or a sunset, and while
it’s true that no direct sunlight is reaching the lunar surface at this moment, earth’s
atmosphere is bending the red wavelengths of
light around the planet, so that redness you see
during a blood moon eclipse is a combination of
light from every sunrise and sunset on earth,
all happening at once. So the moon appears
red for the same reason that sunrises and sunsets on earth are red because of a phenomenon
called Rayleigh Scattering. Named after the British
physicist, John William Strutt, also known as Lord
Rayleigh, who discovered it in the late 19th century. It describes how different
colors of sunlight interact with the earth’s atmosphere. Look at the sky during
daytime, for example. It appears blue because air molecules in earth’s atmosphere scatter
blue light more easily than red, but during sunrise and sunset, the light travels through
more of earth’s atmosphere before reaching your eye
which has two consequences. First, it means more overall
sunlight is scattered, making the sun appear dimmer. That’s why you can easily
gaze upon the sun at sunset compared to at high noon. And secondly, more scattering
means more blue light is scattered away, leaving the
redder wavelengths behind. Similarly, the ring around earth during a total lunar eclipse is red because the sunlight travels
through a long stretch of earth’s atmosphere, from one end of the planet to the other. So rather than fear a blood
moon like the ancient Mayans and Mesopotamians, why not think
of it as a romantic moment? After all, it’s the only time
when you can see the sunrise and sunset simultaneously. (peaceful music)

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