Orange Moon

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astrokid14

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Yesterday, I noticed that when the Moon first appeared last night it was orange. As the night went on it slowly turned grey. I was wondering if anyone could explain this to me.
 
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doubletruncation

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As TFWThom mentioned, it's related to why the sky is blue. The reason the moon appears orangish at the horizon is the same reason that the sun appears orangish during sunset. Molecules in the sky are better at scattering blue light than red light, when you look at the sky during the day the blue light that you see coming from the sky is light that came from the sun but then is scattered by the atmosphere (so it changes direction and goes towards your eye instead of hitting someplace else on the ground and appearing to come from the sun from that location). It looks blue because blue light is scattered more easily than red light (the reasons for this are not very deep, but if you're interested do a search for Rayleigh scattering). At sunrise/set (or moonrise/set) the light from the sun (moon) has to pass through more atmosphere before it gets to you than it does when its overhead, as a result more of the blue light is scattered away and the sun (moon) looks more orangish than it does when its overhead.<br /><br />If you have a bright flashlight or a overhead projector and an aquarium you can see how this works. Fill the aquarium with water and add just a tiny bit of milk to it. Shine the flashlight through one end of the aquarium and notice that if you look through the otherside of the aquarium the flashlight looks orangish (and looks even more orange as you add more milk) while the light scattering out the side of the aquarium looks bluish (particularly close the side of the aquarium where the flash-light is, on the other side it'll look more orange).<br /><br />This phenomenon (redenning of light as it passes through clouds of gas/dust, or molecules of fat in the case of milk in the aquarium) is very common in nature. Stars for example tend to look redder than they normally would when you see them through clouds of dust. You can actually use this fact to determine how much dust there is between us and the stars. <br /> <div class="Discussion_UserSignature"> </div>
 
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