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The question asks why does the full moon appear red sometimes. The moon appears red when it is near the horizon. This answer addresses that aspect of moon reddening. Rayleigh Scattering The moon appears red sometimes for the same reason the sky appears blue. It is due to a phenomenon called Rayleigh scattering, named after Lord Rayleigh (1842-1919). Rayleigh scattering occurs when very tiny particles in the atmosphere deflect light in random directions. The likelihood of Rayleigh scattering is inversely proportional to the wavelength to the fourth power. That means Rayleigh scattering occurs much more prominently in shorter wavelengths of light (blue) and much less noticeably in longer wavelengths of light (red). Consider a beam of white light, made up of photons, passing through the atmosphere. Remember that white light is made up of all the colors in the rainbow. The blue photons are more likely to be deflected in random directions due to the Rayleigh scattering, whereas the red photons are less likely to be deflected. This process of scattering the blue photons creates a filtering effect. Because they are scattered off the path of the beam of light, fewer blue photons travel with the beam of light than red photons. So by the time the light reaches you, some of the blue has been removed, leaving a relative abundance of red light. The more atmosphere a beam of light travels through, the more intense the effect of Rayleigh scattering, meaning the more red (or less blue for you sticklers) the resulting beam of light becomes. Light that travels low across the horizon passes through much more atmosphere than light from directly overhead. Therefore the Rayleigh scattering is more intense when viewing objects near the horizon compared to viewing objects overhead. Red Moon That is why the moon looks redder when it is low on the horizon - the beam of light between the moon and you travels through much more atmosphere at a low angle of inclination compared to when the moon is overhead. Because the beam of light travels through more atmosphere, more Rayleigh scattering occurs, and therefore there is less blue light in the resulting beam of light than red light. Our eyes only register the light that strikes our retina - they do not know what proportion of blue to red light there was at the beginning of the beam of light's journey. Because there is less blue than red when the light strikes our retinas, our eyes record more red than blue, and we therefore see the moon in a reddish color. That is also why the sunset and sunrise appear red - the light from the sun travels through more atmosphere at sunrise and sunset compared to when the sun is overhead. When it is low in the sky, the air filters out more blue from the sunlight than red, and therefore we see a relative abundance of red. Blue SkyNow consider a ray of light passing horizontally high over your head. You do not see this beam of light, because it is not shining at you. But as it travels through the atmosphere overhead, Rayleigh scattering deflects some of the blue photons in random directions. A small proportion of those deflected blue photons are randomly directed toward you. Therefore, when you look up in the clear sky, you see blue. A partial eclipse from the Earth. When the light rays pass over the edge of the Earth they are filtered into more red than pure direct sunlight onto the surface of the moon. When there is a lot of dust or pollution in the atmosphere, a full moon may appear anywhere from buttery yellow to salmon to vivid orange to blood red - ''when it is fairly low in the sky''.

The angle at which you view the moon also contributes to it's apparent color.

You'll notice that as a full moon rises it will lose the reddish hue and retain its normal color. When the moon is low on the horizon you are viewing it through a thicker layer of atmosphere and therefore through more of the particles that happen to be in the air.

Refraction may also have something to do with this, but without further research into this I can't be sure.

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โˆ™ 2009-01-19 04:31:27
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Q: Why does the full moon appear reddish sometimes?
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Related questions

Why does the full moon appear reddish sometimes)?

The change in colour is due to the reflected light from the moon passing through dust in the earth's atmosphere.

When would you be able to see a lunar eclipse?

when the moon passes through the earths shadowAt a full moon... the Earth casts a shadow on the moon causing it to appear reddish brown.

Why does the moon appear sometimes as a crescent and other times as a full circle?

because their are phases were it would be full and some as a crescent

Why is the Moon sometimes out in the day and sometimes at night?

The moon orbits the earth, and so it will appear at various places in the sky, and at various times. Before the new moon, and again after the new moon, there are a few days when the moon will appear in the daytime sky. You will never see the moon in the daytime sky close to the full moon.

How does the moon appear to an observer on earth during a full moon?

Full, large or whole. Maybe the question was meant to be...How would the Earth appear to an observer on the moon during a full moon?

How did the moon appear between the fullmoon and the halfmoon?

It will appear as a Gibbous moon (3/4 of a full moon).

When did the moon appear as an entire circle?

when it's a full moon.

When does the moon appear the brightest?

During the middle of a full moon

When does the moon appear circular?

The moon is a full circle during a full moon. A full moon is also the only time a lunar eclipse can occur.

What is a red moon?

An essentially meaningless phrase. The Moon can appear reddish when it's near the horizon or during a total lunar eclipse.

What phase of the moon comes after the full mon?

The moon in the days before and after a full moon appear as a gibbous moon. A gibbous moon is anything between a full moon and a half moon.

It's not a lunar eclpise so why is there a red moon today?

The moon can appear red for a few reasons. First, when the moon appears reddish and it's low on the horizon, it simply means that our atmosphere is reflecting reddish light onto the moon. Another reason can be things such as forest fires and volcano eruption that's spewed particles into the atmosphere, making the moon appear red.

Why does the moon sometimes look really low and reddish- orange?

Because its setting. (maybe)

Can it be a full moon three nights in a row?

it can appear to be a full moon but it will be slightly smaller each day

When will the next full moon on Halloween night appear?

New AnswerActually it's not common for a full moon to appear on Halloween. Due to the speed of the Moons orbit and the fact that we sometimes have an extra day (leap year).Previous Incorrect AnswerEvery Halloween Night So be Scared

Why is the moon sometimes full?

We sometimes see the moon as a complete circle and then it reduces it shape, this is to the shadow falling on the moon.

Why does the moon sometimes seem blue?

does the moon ever appear blue and if so, why?

How many days after the first full moon does a quarter moon appear?

The third quarter (half moon) occurs about seven days after the full moon.

How many times does a full moon appear?

A full moon appears 12 times a year or once a month.

What does the moon do around the earth once every month?

it becomes a full moon but sometimes the moon becomes full twice.

Why sometimes the moon is crescent and sometimes full?

because of the position of the moon between the earth and the sun. a full moon shows the sun is further off to the side than when it is a crescent

Where in the sky will the full moon appear at sunset in the northern hemisphere?

When the Moon is full, it will rise in the east about the time the Sun sets.

Why did the moon appear to be bigger than usual lately?

Because it was on the night of a full moon.

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Where in the sky will the full moon appear at sunset?

The full moon appears in the western part of the sky at sunset. The full moon will rises over the western horizon as the sun sets.