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Why is the sky blue?

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Re: Why is the sky blue?

#41

Post by munificent »

Really cool article! Tangential:

> “Scattering” is the scientific term of art for molecules deflecting photons. Linguistically, it’s used somewhat inconsistently. You’ll hear both “blue light scatters more” (the subject is the light) and “atmospheric molecules scatter blue light more” (the subject is the molecule). In any case, they means the same thing

There's nothing ambiguous or inconsistent about this. In English a verb is transitive if it takes one or more objects in addition to the subject. In "Anna carries a book", "carries" is transitive. A verb is intransivite if it takes no object as with "jumps" in "The frog jumps.".

Many verbs in English are "ambitransitive" where they can either take an object or not, and the meaning often shifts depending on how it's used. There is a whole category of verbs called "labile verbs" where the subject of the intransitive form becomes the object of the transitive form:

* Intransitive: The bell rang.

* Transitive: John rang the bell.

"Scatter" is simply a labile verb:

* Intransitive: Blue light scatters.

* Transitive: Atmospheric molecules scatter blue light more.

Re: Why is the sky blue?

#42

Post by rob74 »

Great article! I have to admit I had also heard of "Rayleigh scattering", but didn't really know more than that, until today.

Actually, I liked it so much that I went to the homepage of the blog, only to find out that this is the only article. Oh well... I hope there will be more to come!

Re: Why is the sky blue?

#43

Post by aaroninsf »

Not discussed but should be:

Prior to the great oxygenation event, Earth's sky was not blue; it was likely red-orange, carbon dioxide and methane being primary components.

Re: Why is the sky blue?

#45

Post by adrian_b »

Sharlin wrote: post #17
KellyCriterion wrote: post #5

Interesting here is: Actually, for most blue butterflies, it’s not even a pigment-it’s just a trick of the light. Since blue is so rare in the biological world (hardly any plants or animals can produce real blue chemicals), they evolved structural colors. Their wings have these microscopic ridges that reflect blue light while canceling out other colors. It’s basically the same reason the sky looks blue, just built in…

Not just butterflies, birds too! But what selection pressure drove the evolution of these structural colors? Presumably signaling, the opposite of muted, camouflaging colors. Also, as many might know, blue eyes are the result of a lack of pigment (eumelanin). The iris is translucent, but Rayleigh scattering preferentially backscatters blue photons. Green eyes have some pigment, making them a mix of brown and blue.

Also the blood veins that you see as bluish through the skin are blue for the same reason, due to light scattered in their walls.

Re: Why is the sky blue?

#46

Post by erikdkennedy »

munificent wrote: post #41

Really cool article! Tangential: > “Scattering” is the scientific term of art for molecules deflecting photons. Linguistically, it’s used somewhat inconsistently. You’ll hear both “blue light scatters more” (the subject is the light) and “atmospheric molecules scatter blue light more” (the subject is the molecule). In any case, they means the same thing There's nothing ambiguous or inconsistent about this. In English…

TIL!

Debates whether to update the sidenote with an explainer on ambitransitive and labile verbs

Re: Why is the sky blue?

#47

Post by erikdkennedy »

rob74 wrote: post #42

Great article! I have to admit I had also heard of "Rayleigh scattering", but didn't really know more than that, until today. Actually, I liked it so much that I went to the homepage of the blog, only to find out that this is the only article. Oh well... I hope there will be more to come!

There will be! Requests welcome!

(I will almost certainly do one on quantum mechanics, but that's such a big explanation that I want to do some simpler ones first)

Re: Why is the sky blue?

#48

Post by erikdkennedy »

liquidise wrote: post #39
erikdkennedy wrote: post #38

Earlier quoted context omitted.

I'm the writer of the article, and happy to chat. Email is my username at gmail.

Your blog layout, particularly on desktop, is brilliant.

My day job is UI design, so I especially appreciate this

(Is there something in particular you're referring to? I feel like sticky nav and sidenotes aren't particularly unusual?)

Re: Why is the sky blue?

#49

Post by ecshafer »

staplung wrote: post #18

In The Cuckoo's Egg Cliff Stoll recounts an episode from the oral defense of his astrophysics PhD thesis. A bunch of people ask questions but one prof holds back until... """ “I’ve got just one question, Cliff,” he says, carving his way through the Eberhard-Faber. “Why is the sky blue?” My mind is absolutely, profoundly blank. I have no idea. I look out the window at the sky with the primitive, uncomprehending wonder…

"Could you be more specific" is a great question to find out more what the person knows and how they thing. You give an answer that, just due to the nature of knowledge and the limitation of language, has some black boxes. And "could you be more specific" is basically asking to go through the black boxes.

Its like asking how does Java work or something like that? You can go from "The JVM interprets java byte code" to quite a lot of depth on how various parts work if you have enough knowledge.

Re: Why is the sky blue?

#50

Post by kazinator »

It's also not just why the setting or rising sun is red, but why it's yellow when high in the sky. The sun doesn't look yellow when viewed from outside the atmospheric veil.
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