Hey guys,

 

In a lunar eclipse the moon dissappears as it goes through the umbra, but when it is completely inside, it turns red.

 

I am not sure why...

 

 

Lunar eclipse happens when the earth is between the moon and the sun. Technically, shouldn't the moon completely "disappear" (be blackenned out)?

 

Why is it red...?

 

Thanks in advance

 

~moo

Hi Mooey...

 

If I remember... The moon turns red because of the Earths atmosphere. At full eclipse, there is no direct sunlight so the only light it gets is the light that's passing through our atmosphere. The more atmosphere it has to go through, the more scattered the light becomes ending with just the red spectrum getting through. Not too sure why only red though...

 

Bee

Rayleigh scattering, the same reason sunsets/sunrises can be red, and the daytime sky is blue. Light scatter depends on the fourth power of the frequency, so the higher frequencies are scattered more strongly, and red is what's left.

Hi Mooey...

 

If I remember... The moon turns red because of the Earths atmosphere. At full eclipse, there is no direct sunlight so the only light it gets is the light that's passing through our atmosphere. The more atmosphere it has to go through, the more scattered the light becomes ending with just the red spectrum getting through. Not too sure why only red though...

 

Bee

 

 

But then, why is it all-dark at the end of the month..? The way I thought about it, I was sure that the effect in a full eclipse SHOULD be the same as in that time in month when the moon is fully out of the sun's light (in our direction).

 

This question goes for you, too, swansont - I know that in sunsets the sun is red, but lunar eclipse *should* be different -- in a sunset there still *is* light visible, it is just being bent. In a total eclipse, there should be no light from the sun at all, from the position of the earth..

 

No?

 

 

~moo

But then, why is it all-dark at the end of the month..? The way I thought about it, I was sure that the effect in a full eclipse SHOULD be the same as in that time in month when the moon is fully out of the sun's light (in our direction).

 

This question goes for you, too, swansont - I know that in sunsets the sun is red, but lunar eclipse *should* be different -- in a sunset there still *is* light visible, it is just being bent. In a total eclipse, there should be no light from the sun at all, from the position of the earth..

 

No?

 

 

~moo

 

During the time of the new moon you would get a solar eclipse — the moon is between us and the sun. Lunar eclipses happen when the earth is in the middle position, which is at the full moon.

 

Sunsets have visible light, but you can still see it after the sun has set. And the sun actually is below the horizon before it appears to, because of the refraction of the light. The same thing happens with the eclipse — the refraction illuminates the moon a little, and the scattering means the illumination is red.

I've also read that you might see some turquoise color at the edges of the moon just before and after totality in a lunar eclipse. I thought I could make out just a tinge of turquoise myself. This is supposed to be due to the light reaching the moon through the Earth's ozone layer which tends to absorb red but allows blue to pass more easily.

The red color comes from all the earth sunsets. If you were on the moon at that moment you would see the night side of the earth circled by a red ring.

I've also read that you might see some turquoise color at the edges of the moon just before and after totality in a lunar eclipse.

You can see some hint of that on that photo:

It comes from Earth's atmosphere. Particles are refracted and reflected from the sun into the atmosphere.

Today's Astronomy Picture of the Day led me to this link which describes the scale on which these colors are measured, and also provides a brief explanation of why:

 

 

http://sunearth.gsfc.nasa.gov/eclipse/OH/Danjon.html