How 'bout red?

[zhgutas]

OK, last night (1a.m. ish) me and my friend were driving home from a nice fishing break, and most of the way a stunning, huge disk of deeply red moon was hanging in front of us just slightly above the horizon, and looked more like a sun setting into the see :shock: I mean.. that was incredible! I know I've seen this before, but it was loooong ago, and I've completely forgotten there are such stunning events.. Dramatic clouds hanging around, a long lonely road among the crop fields and this moon.. I cursed myself I didn't have the camera.. :crybaby:

Marius

NB to myself. It's about the time to get the darn camera!! :violent2:

[Talitha]

Sounds absolutely stunning, Marius!

I bet you can still see it every time you close your eyes.

[zhgutas]

Sounds absolutely stunning, Marius!

I bet you can still see it every time you close your eyes.

You bet I do! I just wonder, what causes it to "bleed" ? :?

Marius

[Talitha]

I think it's the same thing that gives an eclipsed Moon it's lovely color. If I recall correctly, the Earth's atmosphere absorbs the blues and greens from the sunlight but allows the reds to go through... or something like that.

[gurney]

Yes, that's right Carol.

The other thing to note in terms of the physics though is that at moonset you are looking through a lot of atmosphere. The higher up you look the less atmosphere you're looking through, but at the horizon you're looking through as much atmosphere as possible. So the reflected light from the moon is being massively scattered, which has a double effect:

1. Refraction - because the atmosphere is so thick and the line of sight passes over so close the earth's surface, there is a lot of warm and turbulent air for the light to pass through, leading to a 'wobbly' moon.

2. Scattering of blue light - the dust and pollen in the air very effectively scatters the blue light, stripping blues from the light you see, leaving only the red wavelengths, making it very red.

The effect is most notable during summer and autumn when dust and pollen are in their highest concentrations in the air. Other factors which have a dramatic impact are forest fires and volcanos, but in the UK it's unlikely that they'd be a factor!

[Talitha]

Thanks for the detailed info, Gurney! And I know what you mean about looking through the airmass.. we call it the '30° garbage zone' here.