Light Scattering:  Blocking Stars and Light Curtains

Light Scattering: Blocking Stars and Light Curtains


During the day, the sky appears as a deep blue. Arguably, this is because of the scattering of light by air in the same way that a prism separates the spectrum from visible light to a splash of colour on a nearby wall.

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This sort of bending might also explain the different colours at sunset and sunrise, rather than just angry, approaching weather. Some argue that the sky is blue because it reflects the ocean, and, in turn, the ocean is blue because it reflects the sky, and I tend to agree with all points based on light scattering.

Light polution from cities scatters its colours into the sky, even for several miles, and tends to appear as a lingering yellow smog. This is powerful enough to taint the black of the night sky enough to blot out the stars.

In the north, one may be lucky enough to see the Aurora Borealis (the Northern Lights), or, in the south, the Aurora Australis. Characterised by a searing series of silent curtains of light, this phenomenon has been both sought and feared. There are certain tribes native to North America that will not look at it, as it is thought to be a haunting or ill omen.

How it Works
The mechanics of the wonder are related to magnetism and our atmosphere. Objects that enter the Earth's atmosphere, which has the job of breaking down particles entering, possess a magnetosphere, which is the magnetic field of the object around it. Because of the strong magnetism, the objects are, in turn, pulled toward the poles. Upon entering, the magnetic field meets with the gasses of Earth's atmosphere, and it suddenly becomes energised, and suddenly that very energy is emitted as light, as Fluorescence. Light emitted during all of this tends to be rich with oxygen, resulting in a greenish-yellow colour over all. At lower altitudes, the objects still falling appear as red. If the in-coming object has any sort of nitrogen composition, it will burn as blue or purple.

What colour would you rather the sky be? Have you ever experimented with prisms and the visible spectrum? Have you seen an aurora?


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9 Comments
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i have seen the aurora a few times. i live in northwest ohio, but if there's a large sunspot or storm on the sun it pushes the aurora far enough south to see it. sadly, the last time it was supposed to be visible here we couldn't see it due to light pollution. we drove out of town to where it used to be dark, only to find that the light pollution has extended out there with big flood lights from new factories.

it is gorgeous and awe inspiring when you can see it.
Light pollution blocks out a lot of things that are otherwise amazing ... living where I live now for a little while, looking up enters a whole new world. If you can't tell, the nearest town is about twenty minutes from me, driving quite fast, at that.
i recognise that picture - it's on my desktop! the whole thing is incredibly beautiful...

as for the sky; i love staring at the stars but i live in a city so i have to go a ways out of town to do it. i like coming up with my own constellations
I'm constantly making up constellations. I used to be obsessed with it, actually. I invented a code language for the friends I didn't have to use based on star constellations' names, which are Latin.
I was born in Anchorage, Alaska in the 1950's and lived there until I was eight. I clearly remember the Aurora Borealis and the amazing displays of light where the whole sky was like a moving rainbow. Thank you for your article that explains it.

As an artist I have also noticed something about color in the northern latitudes. I can pretty much tell if a photograph in a book or on the internet has been taken in Alaska. For years I wondered about it until I realised that the further north you go the more of a cerulean blue you notice. It is very sublte. But I think it is because of color changes in the atmosphere caused by light and the curvature of the earth. After moving south to Washington State, I noticed the cerulean blue had reduced. I think it is a bit more cobalt as you go south. I have no idea if there is a scientific basis for this. It is just my own observation.
I'd be curious myself to learn of what you're speaking. It might have to actually do with low-level smog from surrounding cities. I have seen a bold blue sky when I take to hiking in the distant mountains. The towns there don't have any industry to speak of, so the only real pollutants are passing cars.

If you find anything, let me know. I'll look myself.
i saw the aurora borealis whilst flying over the southern tip of greenland on my way to amsterdam/frankfurt. it remains one of the single most beautiful things i've seen in my life. if only the man sitting next to me on the plane hadn't been laying on me and snoring at the time...lovely article. i like it when the sky is a deep purple. almost black, but not quite...
Remnants of the sunset, yes. Shame about the sleeping man.

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