Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Why is the sky blue?

explainers.blog

Post reply on HN
Print view View original

191–200 of 279 posts

Re: Why is the sky blue?

#191

Post by thaumasiotes »

kazinator wrote: post #164
thaumasiotes wrote: post #162

Earlier quoted context omitted.

The article has a section on "why are clouds white?", but it doesn't really address the reason I thought that question should be covered. It just says that clouds act like a collection of randomly-oriented prisms, such that whenever light of any wavelength comes into the cloud, it is dispersed from the cloud evenly in all directions. This would explain why a cloud was white if even white light was coming into the clo…

Well, no; what's coming into the cloud is sunlight, filtered through the atmosphere. It scatters that light and so it has that color. The same like a heap of powdered salt in the palm of your hand, held up to the sun. Clouds illuminated by the setting sun aren't white.

> Well, no; what's coming into the cloud is sunlight, filtered through the atmosphere. It scatters that light and so it has that color.

The model the article describes is:

1. The sun puts out a bunch of light.

2. Light that is lower-energy than blue light fails to be effectively scattered by the atmosphere, and follows a path from the sun to you.

3. Light at the levels of blue and up is effectively scattered by the atmosphere, and comes to you from a random direction.

So if you look toward the sun, you receive light that has been depressed of its blue-and-up wavelengths, and the sun appears to be yellow. If you look away from the sun, you receive light that has been enriched in blue-and-up wavelengths, and the sky appears to be blue. Crucially, the sky looks blue because it is sending you more blue light than the background level.

A cloud that isn't between you and the sun is getting its light from the sky background, which is blue. Why is the cloud not blue? It can disperse all the light it receives evenly, but that light is enriched for blue-and-up wavelengths.

Re: Why is the sky blue?

#192

Post by PetitPrince »

erikdkennedy wrote: post #48
liquidise wrote: post #39

Earlier quoted context omitted.

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?)

> I feel like sticky nav and sidenotes aren't particularly unusual?

Not unusual, but you used them with taste and restraint, like the rest of your layout and animations. That's something that HN comments like, I think. Notice the distinct lack of "OMG some fancy presentation trick ! Litteraly unviewable!" comments that often happens when an unusual layout is presented (and often with reason; but sometime to a fault).

I guess the main praise your page UI is that it looks, well, like a page. But augmented I guess ?

Personnally I really like the way you used a grid to separate the content from the nav. I like that you used both the left sidebar for nav and for the header number (re-using the same space for multiple purpose feels elegant, because those purpose are secondary to the content, if that makes sense). And I like that the grid anchors your eyes by fencing the different chapters along with the nav. (and now that I mention it, it feels weird that the headings are outside their chapters, but it didn't felt like that upon first reading).

Re: Why is the sky blue?

#194

Post by reactordev »

codesnik wrote: post #181
reactordev wrote: post #166

Earlier quoted context omitted.

I have that already ;) it actually looks like muddy puke green than green. However, green stop lights look more “white” than green. Some reds look like brown. I hate reds. I’m not sure about the Pantone-like color matching but I definitely see different colors than most people. To the point where my flight license is restricted. Dichromatic but not trichromatic.

how does dichromatism restricts flight license? no instrumental flights? no night flights? something about perceiving warning lights on some panels?

All three

Re: Why is the sky blue?

#195

Post by reactordev »

lesostep wrote: post #189
int_19h wrote: post #161

Earlier quoted context omitted.

There's some evidence that tetrachromacy already exists in a few humans. If so we have the gene already. But why would it spread?

fringe theory just for a bit of fun: since screen use 3 colors diodes, maybe people with tetrachromacy would be less addicted to screens, making them both more grounded in real life and marginally more successful, leading to them having more children? I have no idea how to test it. But in my heart I know that screens with RG, GB or RB color models would suck enough that any screen addiction would be cured instantly.

I wouldn’t be so sure, for a decade all we had was G and we used more and more of it until we died of dysentery outside Eagle River.

Re: Why is the sky blue?

#197

Post by tim333 »

lesostep wrote: post #189
int_19h wrote: post #161

Earlier quoted context omitted.

There's some evidence that tetrachromacy already exists in a few humans. If so we have the gene already. But why would it spread?

fringe theory just for a bit of fun: since screen use 3 colors diodes, maybe people with tetrachromacy would be less addicted to screens, making them both more grounded in real life and marginally more successful, leading to them having more children? I have no idea how to test it. But in my heart I know that screens with RG, GB or RB color models would suck enough that any screen addiction would be cured instantly.

They need special screens with four colors and the internet updated to make it more interesting for the tetrachromatic.

Re: Why is the sky blue?

#198

Post by 6stringmerc »

jstummbillig wrote: post #74
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…

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.

Hard truths are not desirable and I pity and envy your naitivity.

Re: Why is the sky blue?

#199

Post by 6stringmerc »

brabel wrote: post #76
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.

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 grew up with Mr Rogers

Gen Z grew up with Mr Beast

We are proper doomed mate.

Re: Why is the sky blue?

#200

Post by msl »

srean wrote: post #65
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…

I have always wondered about this. The verb for the first person is to 'see'. To a third person you 'show' For the first person there is 'listen' (or 'hear'). Does English not have a corresponding word for the third person ? What about Germanaic or Nordic languages ? Do they have a third person analogue of 'listen' ?

In Finnish you might use "kuunteluttaa". You start with "kuunnella", "to listen" and inflect it in the way that turn a verb into "make someone verb". This particular example is a little unusual, but the same thing is commonly used with e.g. "taste". It works with all kinds of verbs, so it comes handy when you want your car serviced or your house painted.
Post reply on HN