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Why is the sky blue?

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Re: Why is the sky blue?

#201

Post by 1718627440 »

srean wrote: post #73
smlavine wrote: post #70

Earlier quoted context omitted.

"tell"?

Ah! That's not bad but it's not the same thing. Good nevertheless. I can 'show' (or point someone to a) a sight that I am not myself creating in anyway. The word I am looking for would mean to 'make you hear' in the same may to show is to make you see. I showed him the distant tower. I ??? him the faint sound.

As the sibling points out show works for audio as well. Also vision is directed while audio is not. You need to look at some thing specifically in order to see it, you do not need to turn your head, to listen, the sound needs just to be there. You might need to alter your perception filter for both.

Re: Why is the sky blue?

#202

Post by fransje26 »

lamontcg wrote: post #169
jstummbillig wrote: post #74

Earlier quoted context omitted.

I am positively excited about the upcoming first generation of humans who will have all their questions answered, correctly and in the way they can best understand, and as often and many of them as they want – and what that is going to enable.

Sometime around 1992, I wrote a college essay on how the Internet was going to wipe out ignorance and enable true democracy...

Ah, crickets! Just got the two nouns in the wrong order..

Re: Why is the sky blue?

#203

Post by tim333 »

beders wrote: post #83
erikdkennedy wrote: post #27

Earlier quoted context omitted.

Yes! This is exactly why I wrote this article :) Any other questions give you the same disappointment?

How can light "bounce off" something if it doesn't have mass?

The rest mass is zero but photons have momentum when moving.

Re: Why is the sky blue?

#204

Post by 1718627440 »

tsoukase wrote: post #84
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…

Labile verbs is a source of ambiguity of natural languages (only western ones?) that we are all accustomed to. The bell rang should become The bell was rung, either way it means The bell rang another bell.

That ambiguity results from the elimination of cases, other languages still have them (and I perceive English to have as well, I just treat them all as homonym). You wouldn't say that foo(a,b) has ambiguity, because foo(NULL, &b) and foo(&a, NULL) both exist.

Re: Why is the sky blue?

#205

Post by tim333 »

kgwgk wrote: post #172
__MatrixMan__ wrote: post #130

Earlier quoted context omitted.

There are differences in receptor behavior across species, but they are understandably clustered around the parts of the spectrum in which sol is most luminous. An earth-like planet orbiting a different star would likely have evolved photoreceptor arrangements which match that star instead. So after scratching the biology itch we'll probably need to talk about fusion byproducts in sol-like stars.

> they are understandably clustered around the parts of the spectrum in which sol [sun] is most luminous That would be understandable but it’s not what’s going on: http://hyperphysics.phy-astr.gsu.edu/hbase/Chemical/watabs.h...

Ah - so I guess that's why snakes have pit sensors for infrared.

Re: Why is the sky blue?

#206

Post by piokoch »

The interesting part is not that much Rayleigh scattering - it is obviously very important, but the better question was on WHAT THE HELL light is scattered. Rayleigh had some ideas, like some "dust" that is in the atmosphere, etc.

One day, long time ago, a now forgotten Polish physicist Marian Smoluchowski [1], was on the walk in the Alps Mountains (except being physicist he was a professional mountain climber/hiker), he looked at the sky and said - no freaking way, there is no dust over there.

So he started thinking and thinking (and Albert Einstein said, after premature death of Smoluchowski, that he was the best thinker he knew) and this moved him into consideration of fairly fresh and new branch of physics at that time - quantum mechanics.

As it turned out, that was it. He figured out that light is scattered on quantum fluctuation of the air density, what explained fully blue color of the sky as well as gave a birth to critical opalescence theory.

[1] https://en.wikipedia.org/wiki/Marian_Smoluchowski - if Smoluchowski hadn't died early, in 1917 from dysentery, he would have been better known, as he would have been awarded three Nobel Prizes (in physics and chemistry), as researches he did were awarded (other guys get the prize).

Re: Why is the sky blue?

#208

Post by 1718627440 »

mrb wrote: post #115

I dislike with passion the answer "because Rayleigh scattering". When someone asks why, especially if a child asks, the default answer should be the simplest correct answer : Because it's the color of the atmosphere, specifically nitrogen and oxygen! It's technically correct to state this. Gasp! But aren't nitrogen and oxygen usually described as "colorless"? Well, yes but... If they were perfectly colorless, the sky…

At least my mental model of color before I learned the details in physics and chemistry was that of a property of surfaces, so your explanation wouldn't have served me. I would have expected, that the light becomes blue as part of the transition from "empty space" into "air", not as part of the "flight" through the air.

Re: Why is the sky blue?

#209

Post by 1718627440 »

beders wrote: post #83
erikdkennedy wrote: post #27

Earlier quoted context omitted.

Yes! This is exactly why I wrote this article :) Any other questions give you the same disappointment?

How can light "bounce off" something if it doesn't have mass?

https://en.wikipedia.org/wiki/Huygens%E2%80%93Fresnel_princi...

The light "beam" we perceive is the result of infinite circular waves. The points were the light is not are points where they cancel each other out. We had that as part of the school curriculum, do you not have that, or did you forget?

Re: Why is the sky blue?

#210

Post by eru »

mncharity wrote: post #125
brabel wrote: post #76

Earlier quoted context omitted.

The same anticipation of great things happening preceded the arrival of widely available internet, but all we really got was cat videos initially, and doomscrolling more recently. I don’t have much hope for great things anymore.

I saw a Microsoft talk decades back, that was a dispirited "the people of India could be buying educational materials and... but no, all the money is in ringtones". For some kinds of business perspective, ok I guess. But for others, and for civilizational change, what's going on in the tail can matter a lot. Does China become a US engineering/science peer in early 21st C absent an internet/WWW?

Well, the thing is that the educational materials are largely free. That's why the people of India don't need to buy them.

Isn't that a better world than one where the ringtones were free?

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