Talk:Diffuse sky radiation

message: The principle explained begs further clarification on 2 points:
"The sunlit sky appears blue because air scatters short-wavelength light more than longer wavelengths."
Question: Why is this?
"Near sunrise and sunset, most of the light we see comes in nearly tangent to the Earth's surface, so that the light's path through the atmosphere is so long that much of the blue and even green light is scattered out, leaving the sun rays and the clouds it illuminates red." 
Question: Why then, does the sky not turn green and yellow first, before turning red in the evening?
Jakkeven (talk) 05:59, 7 October 2010 (UTC)
replies: text: The "equivalence" is not a spectroscopic one, but concerns the visual color appearance, as it is clear by the quoation reported. I'll try to clarify this in the article. Anyway, the spectrum reported is shifted towards shorter wavelengths, with respect to the spectrum of sunlight.  --GianniG46 (talk) 16:12, 2 February 2011 (UTC)
thread_title:  Clarification please 

message: This is taken from the excellent public domain NASA resource DICTIONARY OF TECHNICAL TERMS FOR AEROSPACE USE at http://roland.lerc.nasa.gov/~dglover/dictionary/content.html
:Karada, are you sure this public domain material? -- looxix 00:04 Apr 18, 2003 (UTC)
::It's USA government material. It's fine. HereToHelp 00:57, 28 September 2005 (UTC)
thread_title: Initial comments

message: Can I suggest that instead of cleaning this article up, it is merged with the other sky background article (airglow)? Rnt20 06:48, 7 October 2005 (UTC)
thread_title:  Merge with [[airglow]] 

message: The article claims that a relativistic correction is required to account for the blueness of the sky.  I don't think this was shown anywhere in Einstein's work on scattering.  Relativity has nothing to do with it.  I am therefore removing the statement on the relativistic correction.  DonSiano 18:15, 17 March 2006 (UTC)
thread_title: Einstein and blue sky

message: If what is said is true, then why isn't the sky violet? This would seem to be correct, since the article says air scatters shorter-wavelength light in preference to longer-wavelengths. Matthew 00:17, 19 April 2006 (UTC)
replies: text: See 'the sky is purple?' question below for a continuation of this. ADNewsom (talk) 03:23, 11 June 2014 (UTC)
thread_title:  Layman Question 

message: why isn't the sky ultraviolet, that is, transparent to us ?
86.104.188.234 17:39, 29 April 2006 (UTC)
thread_title:  half-layman question 

message: Ref from article:<<Approximately 23% of direct incident radiation of total sunlight is removed from the direct solar beam by scattering into the atmosphere; of this amount (of incident radiation) about two-thirds ultimately reaches the earth as photon diffused skylight radiation.[citation needed]>>
Means 23%*75%=roughly 15% the light is coming in scattered form not a direct rays. 
Two arguments against: I personally have measured the sun given flow from sun-size collimated spot where sun is, and compared it to identical size non-sun containing spot, both luminities. Extrapolating this small angle to whole semi-sphere gives figure that about 50% is scattered light output in to comparizon with direct sunlight, not any 15%. Measurement accuracy was about +/- 10% thus confident interval is 45-55% of direct sunlight. The geographical place where measurement was done, aprox 57 N and 21 E, summer.
Second argument is (are) plethora of different Solar Panels producers texts where they swear the productivity of photovoltaics in scattered daylight is about 50% of the same at direct insolation case. And not the 15%.
The only case when indeed something near the 15% is possible, is when strong lower atmospheric layer clods are abundant so much the meteorologists says "strongly cloudy day". (Dont miss with heavy rain-clouds, when 1000x weaker light even is possible).  — Preceding unsigned comment added by 5.179.10.194 (talk) 13:32, 22 May 2023 (UTC)
thread_title:  Figure what is highly suspicios

message: I moved the paragraph below here from the article. It doesn't seem to fit with the more common explanation of the blueness of the sky in terms of the wavelength dependence of Rayleigh scattering, as given in the article. If someone can adjust the text so that it's clear how these ideas fit together, this might be fine, but as it is it's just confusing.--Srleffler 15:27, 2 September 2006 (UTC)
thread_title:  Section moved from article 

message: The included spectrum seems misleading, from the lengthy caveat: It was taken behind four panes of glass, so anything below 400nm is not shown. 
My question is: if scattering is stronger for smaller wavelengths, wouldn't UV light be scattered most? If this is the case, I would think that it is important to present here if only to warn people of the danger of skin cancer being outside in a shady area. 121.44.119.136 21:32, 3 December 2007 (UTC)
replies: text: That would be why you can get sunburned on a cloudy day. :) 98.246.109.37 (talk) 10:33, 1 May 2009 (UTC)
thread_title:  Risk of skin cancer in the shade?? 

message: I removed this line from the article because it doesn't make much sense.  The ocean can appear blue because it's reflecting the sky.  It almost makes it sound like the ocean itself emits light regularly.  "This is partialy also because of the ocean and how deep it is making it appear blue on the surface whilst blue light is filtered into the atmosphere." Ghiles (talk) 06:02, 28 February 2008 (UTC)
thread_title:  Ocean emitting light? 

message: There is an image at the bottom of the article showing an overcast sky. However, it has a strong blue tinge and I don't think this is accurate. It would be quite easy to get a photo of a blue overcast sky through either incorrect white balance settings on the camera, or through image manipulation, but I don't think it is common for an overcast sky to be blue. The only time I can remember seeing a similar sky is after sunset, where (this is just my guess) the weak blue scattering of the upper atmosphere is then filtered through the clouds, but there is no direct sunlight on the clouds as the sun is now below the horizon. If this is indeed the case with the image in question, then it should be explained as such, but it is misleading to just caption it 'overcast sky' because it probably leads readers to wonder why it is blue when overcast skies are usually neutral. Please do let me know if I've misunderstood the phenomenon. Diliff   | (Talk)   (Contribs) 14:59, 26 August 2008 (UTC)
replies: text: I agree.  It's probably just poor white balance.  Maybe a better picture would include some other object in the foreground, as a reference.  Spiel496 (talk) 17:43, 26 August 2008 (UTC)
thread_title: Image of the overcast sky

message: "Scattering varies as a function of the ratio of the particle diameter to the wavelength of the radiation. When this ratio is less than about one-tenth, Rayleigh scattering occurs in which the scattering coefficient varies inversely as the fourth power of the wavelength. At larger values of the ratio of particle diameter to wavelength, the scattering varies in a complex fashion described, for spherical particles, by the Mie theory; at a ratio of the order of 10, the laws of geometric optics begin to apply."
That's some fancy word speak but it doesn't help the average reader understand anything.  —Preceding unsigned comment added by 65.23.116.46 (talk) 06:38, 7 February 2009 (UTC)
thread_title:  Huh? 

message: This is a very true comment. CamrynRocks! (talk) 17:54, 19 April 2010 (UTC)
thread_title:  I agree 

message: The last paragraph of the introduction was originally
:The important processes in the atmosphere (Rayleigh scattering and Mie scattering) are elastic. No energy transformation results, only a change in the spatial distribution of the radiation.
The second sentence isn't quite right, so I removed it.  Elastic scattering does not mean no energy transfer, it means no energy is transformed from kinetic energy to some other form (such as bind energy), or vice versa.  In particular, air particles may very slightly decrease the energy of the scattered photon, although I believe this will be imperceptible.  I welcome anyone who would like to rewrite the second sentence. Njerseyguy (talk) 23:54, 16 November 2010 (UTC)
thread_title:  Elastic scattering 

message: I understand that this article is talking about Earth because it's a great example of this, but surely the process isn't Earth specific, which is the strong implication of how the article is currently worded.
There is currently no indication that this process applies to any other body with an atmosphere or that the Earth's details are merely an example of it.
Should the article be updated to account for this?  -- Shhac talkcontribs 18:10, 4 July 2015 (UTC)
thread_title:  Not Earth Specific 

message: The section "As a part of total radiation" appears to me to be relatively unconnected to / interwoven with the context. Furthermore I cannot see a (clear) explanation and definition of certain quantities and terms, e.g.:
* "total solar radiation" here is (apparently) meant to be limited to radiation hitting a plane that is at an angle with the horizontal;
* "β is an angle from the horizontal" is not meant to be some viewing angle indicating a position in the sky but appears to be related to the tilt of a radiation receiving plane. 
My first impression on reading the paragraph was that it was going to give (an approximation for) the radiant emittance of diffuse sky radiation as a function of zenith angle and azimuth angle.
Only after consulting the source mentioned, I have reached the conclusion that the formulae are actually meant to give an approximation for the amount of radiant energy hitting a plane surface whose normal is at an angle β with the local upward direction, and then probably only when this tilt is in a north-south direction.
While this information in itself is interesting to me, I am not at all convinced it belongs here (in its current form).Redav (talk) 13:10, 23 December 2020 (UTC)
thread_title:  Issues with paragraph "As a part of total radiation"  

message: Why isn't there a similar change in the Keeling curve after this similarly large volcano. 2601:280:5E01:D120:41F3:4215:3BA3:DD53 (talk) 15:10, 2 June 2024 (UTC)
thread_title:  What about El Chichon in addition to Mount  Pinatubo?