Talk:Sunlight/Archive 1

Archive 1

Cold and hot countries edits

(next two items are copied from user pages)

"In cold countries most people like sunshine and prefer not to be in the shade. In hot countries the converse is true and the midday hours people preferably stay inside, because it is too hot to go out."

I dont mean to sound arrogant or anything, but I dont think adding that to the article about Solar radiation was a very relevant contribution. What you wrote was your opinion and it is fine, but an encyclopedia should have non-biased factual information. Again, I hope you dont take it offensively, but I have removed it.

Nice to see kind people on wikipedia contributing to articles, and you seem to have done alot of good work.

Jedi Dan 16:39 Apr 23, 2003 (UTC)

---

I had my doubts about Patrick's addition at solar radiation too, and at first the only reason I put it back in after the edit conflict was because I know he generally does good work, and wouldn't put something like that in just to be a smart aleck. Then, figuring there must be some reason for what he did, I checked the "What links here" for that page, and sunshine is, sure enough, a redirect to solar radiation, so I would think he'd put that in there for people who followed that redirect to get there. -- John Owens 16:52 Apr 23, 2003 (UTC)

---

Adding to that, actually, it seems to me that Patrick's contribution is possibly even more relevant. After all, most of the current content is about the solar fusion that produces the radiation, than the radiation itself. Don't get me wrong, I love knowing more details about the process, but Patrick's bit is at least as relevant to the article title (and especially the redirect) as Jedi Dan's. Now that I see that solar fusion doesn't exist yet, perhaps some of this could be moved there? Or moved into fusion, and make solar fusion a redirect to that? -- John Owens 17:13 Apr 23, 2003 (UTC)

---

There is already quite about about fusion at Nuclear_fusion and my article was meant to really be an overview about fusion and how it relates to solar radiation rather than anything in depth about the process. I suppose I perhaps put a bit too much irrelevant information in myself, I dont mind if someone wants to reorganise things or move it about.

Jedi Dan 23:19 Apr 23, 2003 (UTC)

Mention of Insolation

Insolation is mentioned and a global quote is given as 342 W/m^2. However, insolation is never given in W/m^2. Instead, it is given as a measure of energy, and therefore in kWh/m^2. Even the link to the insolation page says as much. Kopasa 13:51, 19 June 2007 (UTC)kopasaKopasa 13:51, 19 June 2007 (UTC)

In fact, I'm fairly certain that the distribution across the cross-section is an incorrect calculation. It really makes no sense and to quote the DoE website "The radiation that reaches sea level at high noon in a clear sky is 1000 W/m2", and the solar constant is given as 1367 W/m^2 with no mention of a distribution across the cross-section. Kopasa 12:56, 20 June 2007 (UTC)kopasaKopasa 12:56, 20 June 2007 (UTC)

I removed the section pertaining to the incorrect insolation reference. Kopasa 13:01, 20 June 2007 (UTC)kopasaKopasa 13:01, 20 June 2007 (UTC)

Hmm. 342 is correct, and the page explains why. Expressing it in w/m2 is also correct. Calling *only* this insolation is odd though William M. Connolley 13:04, 20 June 2007 (UTC)

342 is correct answer for a calculation that is incorrect. the incident solar radiation is not averaged over the cross-section to find the insolation. all refs (including the one i used above, the Dept. of Energy) use the solar constant as a measure of the energy incident on any portion of the upper atmosphere.

also, calling the answer the insolation is incorrect, as even clicking the link to insolation will show. insolation is a measure of solar energy, and is measured in the SI joule/m^2, or the more standard kWh/m^2. calling this solar irradiance would be more appropriate, and would be 1367 W/m^2 for the top of the atmosphere, and ~1000 w/m^2 for the surface of the earth.

This all said, deletion of this misleading calculation is highly recommended. Kopasa 13:50, 20 June 2007 (UTC)

I strongly disagree: that the average solar flux at TOA is 342 is well worth noting. Whether we call it insolation or not I care little about. I would call it insolation; and I would measure it in w/m2 not w/m2.s. I doubt there is uniformity over this William M. Connolley 13:57, 20 June 2007 (UTC)

If you had ever read anything else on solar energy, you would be very aware of this difference and how misleading it is. perhaps you would also be aware of the constant uniformity of the terminology in regards to research on the subject. the calculation is one i have not seen reproduced anywhere, so a single reference to its validity would be appropriate. until then, it remains mislabeled and therefore greatly misleading.

That said, i do agree that calling it the average flux, making sure to note that this calculation includes the half of the planet not receiving radiation from the sun, would be appropriate. Kopasa 14:16, 20 June 2007 (UTC)kopasa

made a few changes taking into account the terminology discrepancies as well as deleting a redundant initial sentence whose entire content had been covered but the final sentence of the preceding paragraphs. hope this is better! Kopasa 14:58, 20 June 2007 (UTC)kopasa

Confusion

Because the surface area of a sphere is 4 times the surface area of its cross-section, the temporally and spatially averaged insolation over the Earth's surface above the atmosphere is a quarter of this value, 342 W/m²

I can't for the life of me understand this sentence. Does cross section mean diameter, this is the first mention of insolation and could it be replaced with "incoming solar radiation (insolation)"? I don't know much about this so I thought I'd best leave it alone but could someone please change it? I've put a heading on a previous talk topic, if this is offensive feel free to delete it. Rex the first 23:43, 20 December 2005 (UTC)

Do the changes I've made make it clearer? Dragons flight 00:16, 21 December 2005 (UTC)

I thought my sentence was a model of concision and clarity :-) To be picky,

The Earth recieves a total amount of radiation determined by its cross section (π R²), but averaged over time this energy is distributed across the entire Earth's surface area (4 π R²).

is slightly misleading, in that: averaged over time this energy is distributed across the entire Earth's surface area implies (to me) even distribution; averaged over time the insolation is uneven wrt latitude. William M. Connolley 09:50, 21 December 2005 (UTC).

I think the newer edit makes more sense but maybe you could add "even though the insolation is uneven wrt latitude" or something like, thanks anyway! Rex the first 16:06, 21 December 2005 (UTC)

(Recent comment about 10^17 W moved to new section further down. Han-Kwang (t) 00:47, 15 November 2007 (UTC))

Moving stuff to Nuclear fusion

(William M. Connolley 20:37, 24 Jul 2004 (UTC)) I removed a load of stuff to nuclear fusion which I thought was fair... but I'm willing too be disagreed with.

Carcinogen

Just a note that solar radiation is brought up as a IARC Group 1 carcinogen in the list there, but there's no talk about its carcinogenic nature to humans here about UV light exposition. This article is also not member of the Category:IARC Group 1 carcinogens category. I'm not sure of in which extent this information should be added though, so I'm just bringing it up here as a heads-up for now. I'd probably expect to read something about the solar radiation risks to humans here, although I'm not sure it's actually supposed to be in the Group 1 Carcinogen category and all. -- Jugalator 02:41, 22 December 2005 (UTC)

Perhaps there should be a section on the biological effects of various parts of the spectrum. (SEWilco 07:58, 23 December 2005 (UTC))

Merging Sunlight

• Opposed: Solar Constant and Solar Radiation are close enough to each other to warrant merging. However, Sunlight is clearly a distinctively different subject. It is the sort of article that a six-grader would go to for information on the nature of sunlight. Trying to merge a scientific discussion of the solar constant into Sunlight is unwarranted. What should ocurr is Solar constant should be expanded with all the information from Solar radiation and Solar radiation should be tossed. This way, you have two distinctive topics: Sunlight and Solar constant. Greg L 17:25, 24 October 2006 (UTC)
• Oppose: Keep the solar radiation technical and the sunlight non-technical, with directs to solar radiation for details.+mwtoews 20:14, 29 December 2006 (UTC)

Merging Solar constant

• Agree: Solar Constant and Solar Radiation are close enough to each other to warrant merging. Greg L 17:25, 24 October 2006 (UTC)
• Agree: Similar content; same physics.+mwtoews 20:14, 29 December 2006 (UTC)
• Disagree: Isn't this constant important enough to warrant its own article? Also what about Sun unit? —Preceding unsigned comment added by 141.213.247.14 (talk) 22:10, 8 October 2007 (UTC)

Solar Constant values being associated with "winter" and "summer" is silly. Who's summer or winter is being referenced? The larger value is associated with the Earth reaching perigee and the smaller value with Earth reaching apogee in its orbit around the sun. 67.166.28.214 21:28, 13 April 2007 (UTC)

Effect on Climate

The first paragraph of this section does not really address the question of how solar variability affects climate. To me it could be left out and nothing would be lost. Birdbrainscan 05:16, 27 January 2007 (UTC)

Sunfall

Notwithstanding the prior use of this word in connection with a series of novels, I think that the cummulative total of radiant energy incident per unit area over a stated time should be termed "sunfall" by analogy with the term "rainfall".

The obvious units (solar full spectrum) are joules per square meter per second, but a better term might be, "apollos", for example. —The preceding unsigned comment was added by 70.157.183.102 (talk) 03:07, 16 February 2007 (UTC).

We don't invent terminology here. Got a published description of a unit of measure? (SEWilco 04:19, 16 February 2007 (UTC))

Langley's Solar Constant

Am wondering if the reports of Langley's solar constant could be clarified. The value of 2.54 cal should be cal/min/cm^2. The per minute per cm^2 part seems to be missing. The current value of 1366 W/m^2 of the main text translates to 1.958 cal/min/cm^2, consistent with other information, including the picture explanation Skeptiker 22:57, 16 February 2007 (UTC)

Fix it. I think "2.54 cal" was in the source material, which was a summary which probably assumed the rest. (SEWilco 04:32, 17 February 2007 (UTC))

Fixed! Hertz1888 02:37, 22 July 2007 (UTC)

Solar irradiance spectrum above atmosphere and at surface

This is a very nice graph -- would be even nicer if someone could add bounds for the visible portion, and label the UV and IR ends, for us casual browsers.-69.87.199.249 12:49, 10 May 2007 (UTC)

Even better would be to annotate also with a color bar, for the visible part.-69.87.203.17 20:03, 27 May 2007 (UTC)

I am curious why this page includes two graphs of solar irradiance at TOA. I have my doubts about the top one. Second one shows peak irradiance in visible range where it belongs, the top one shows peak in infrarad range. Don't understand the author's comments about shifting peak due to change in variable, is it possible bad "line by line computations" occurred during this step? -Wjifkri Wjifkri 21:39, 5 September 2007 (UTC)

If you look closely, you will see that the upper graph is plotted as intensity versus wave number (the reciprocal of wavelength, analogous to frequency), and the lower graph shows intensity versus wavelength. The horizontal units and linearity are different, and infrared is to the left on the upper graph, to the right on the lower one. Not bad computations at all, just two different ways of presenting the data, making direct comparison a bit awkward. Presumably each way has its advantages. Someone else will be better able to explain that aspect. I hope this helps. Hertz1888 23:24, 5 September 2007 (UTC)

I noticed the change in variables and understand the inverse relationship of frequency and wavelength. Not surprised that graph experiences some changes, however, the sun does not shine differently because a different variable is used. Why should the peak move from visible range (.5 micron, wavenumber 20000) to infrared (1 micron, wavenumber 10000)? Wjifkri 14:25, 6 September 2007 (UTC)

That's because the surface under the graph has to be conserved. For example, the area between 400 and 600 nm only spans 200 nm, but it corresponds to a span of 8333 1/cm. On the other hand, the range 0-1000 cm-1 corresponds to an infinite wavelength range starting at 10000 nm. In order to preserve ratios of surfaces under these two intervals, the curves have to be adjusted, which also changes the peak position. Formally:

$I(\lambda )d\lambda =I'(\nu )d\nu =I(1/\nu )|{\frac {d\lambda }{d\nu }}|d\nu =[I(1/\nu ){\frac {1}{\nu ^{2}}}]d\nu ,$

where I is the curve in wavelength units, and I' the curve in inverse-wavelength units. Han-Kwang (t) 21:57, 6 September 2007 (UTC)

I got it now. Took the time to work out some points to get a feel for the numbers. Should have done that first. Thanks to all and sorry for the distraction. Wjifkri 04:18, 7 September 2007 (UTC)

On this subject you can also consult the article and discussion page for Wien's Displacement Law, where they tackle this question head-on. Question: I dug around on Google Images and all I could find were graphs like the one included in this article of intensity vs. wavelength. Is there a reliable source with an experimental plot or table of sunlight's intensity vs. frequency? Even better, one that compares that plot against the blackbody spectrum vs. frequency. I think having the vs. frequency and vs. wavelength plots side-by-side would help make readers aware of the distinction. --Error9312 (talk) 20:54, 15 December 2008 (UTC)

This is an important error: The curve showing the effective blackbody temperature should be redrawn; it's much too cold! In this graph, the B(lambda)(T) for the sun is too low; you can see that the intensity above the atmosphere (yellow) in much of the visible range is ABOVE the blackbody curve B(lambda)(T), which is nonphysical. (It is true that the corona does have some emission lines, but it's orders of magnitude too dim to contribute all that extra flux.) If this were redrawn with B(lambda)(5780 K) the actual above-atmosphere spectrum of the sun would sit nicely BENEATH the blackbody curve, where it should. The correct effective surface temperature of the Sun is about 5800 K; the Wikipedia article on the Sun gives it as 5780 K; see Sun/2nd paragraph. —Preceding unsigned comment added by 128.146.238.241 (talk) 20:39, 30 June 2009 (UTC)

data sources

Where can one find real-time solar radiation data for any spot on the surface of the Earth? Where can one find online calculators that take location date and time as input and output predicted-modeled-average and predicted-modeled-maximum.-69.87.203.17 20:03, 27 May 2007 (UTC)

"Pysolar is a collection of Python libraries for simulating the irradiation of different parts of the earth by the sun.

As of June 3, 2007, it has two parts:

• A library that, given a date, time, and and earthly location, calculates the location of the sun
• A library that, given a panel spacing and dimensions, calculates the shading percentage as a function of time for a row of 2-axis tracked panels"

[1] -69.87.200.198 00:21, 6 June 2007 (UTC)

Anon edits

Re this [2]: This would suggest the energy from solar power is enormous. is just too colloquial. Solar radiation reaches the Earth's upper atmosphere at a rate of 1366 watts per square meter (W/m2) has already been said higher up in the article. The bit about fission reactions is WP:OR and not obviously relevant William M. Connolley 13:52, 17 June 2007 (UTC)

The most recent version also indicated that the author has no idea how many atoms are involved in a nuclear reactor's activity. (SEWilco 13:58, 17 June 2007 (UTC))

Removed again. There is already an estimate of the total power flux, higher up, which is more meaningful than a count of unspecified "nuclear collisions". --Heron 14:49, 17 June 2007 (UTC)

Total?

It would be helpful to have a number of total solar radiation that hits the earth in 24 hrs. Not in units of power, but in units of total energy (joules?)

13?? * pi * r^2 * 86400 (j/s/m2 * m2 * s = j) William M. Connolley 16:34, 16 July 2007 (UTC)

Ah, thats above the atmosphere, of course William M. Connolley 16:34, 16 July 2007 (UTC)

Solar irradiance per capita

A value of 6000 W for total solar energy reaching the earth's atmosphere "per human on the planet" was added to the article, together with a reference citation giving global average energy consumption as 2000 W per capita. Evidently (tell me if you disagree), a gross calculation error was made, and I have undone this edit. From the Earth article we obtain a surface area of 510 E06 sq. km = 5.1 E14 m2. Multiply by 342 W/m2 and divide by world population of 6.6 E09, and the result is ~ 26 MW (Megawatts) per capita. Alternatively, the earth's cross-section intercepts 1.74 E17 W, per the solar constant section. Divide this figure by 6.6 E09, and the result is the same, ~ 26 MW per capita. Present energy needs for the entire planet would be met by the solar energy incident on one of the smaller countries or American states, properly harnessed. Hertz1888 01:47, 3 August 2007 (UTC)

Sorry, my bad. I did the calc and came up with a "wow" number, but unfortunately I had used 6E12 instead of 6E9 for the population. 7 years working for an engineering company seems to have fried every brain cell connected with math. I swear they're making me senile. AllGloryToTheHypnotoad 19:10, 3 August 2007 (UTC)

Brain fog is not uncommon, AllGlory; I wish you a complete and speedy recovery from yours. Speaking of "wow" numbers, the quantities here - and all other astronomical numbers - are so mind-boggling, it's hard to imagine how any human can handle them. Manipulate, yes, but truly grasp? And yet (a thought for the day), as far as we know, human consciousness is the best resource the universe has for being aware of itself! Hertz1888 04:31, 4 August 2007 (UTC)

Give the human race twenty thousand years and a few near-extinction events, and maybe. But right now we're still just mammals with a tool-making fetish. We're still picking fleas off each other and stealing each other's fruit. AllGloryToTheHypnotoad 17:25, 4 August 2007 (UTC)

how much of solar radiation is heat?

From what I've heard, the 1,366 W/m² of solar radiation consists of light (both visible and invisible) and heat. However, does anyone know exactly what percentage of the solar radiation received by the Earth is heat? I found a source saying that 60% of solar radiation is heat, but another editor said that it was incorrect. --Ixfd64 01:15, 14 September 2007 (UTC)

What I said was that the cited source was restricted (inaccessible)-- Wiki discourages referencing sites needing login -- and that the statement was vague. This is because giving a percentage of the total solar radiation that is heat is far from a simple matter. It depends on how heat is defined (and transferred and absorbed). There are a variety of definitions of heat, none necessarily leading to a specific percentage of solar energy. Giving a percentage without properly defining the conditions would not be encyclopedic. Hertz1888 01:54, 14 September 2007 (UTC)

Are you talking about this link? This is strange; I wasn't asked to log in when I accessed that site. I'm guessing that certain IPs (the one I'm using right now belongs to the University of California, Berkeley) are automatically granted access. --Ixfd64 02:48, 14 September 2007 (UTC)

Correct. This is as far as I (an off-campus user) can get: "Access Restricted"... "This article is available through Project MUSE, an electronic journals collection made available to subscribing libraries." How does the article define heat? Distinguish it from light? Hertz1888 03:05, 14 September 2007 (UTC)

The article said that "sixty percent of solar radiation is transmitted through heat." Other that that, there isn't any other relevant information. Come to think of it, that article probably isn't a very reliable source at all. --Ixfd64 03:53, 14 September 2007 (UTC)

It doesn't really make sense, distinquisch light from heat, ebcause all of the radiation of the sun is actually heat radiation and also light can be converted to heat. --MrBurns (talk) 17:31, 17 April 2009 (UTC)

Number in W

I am having some confusion about the number 1.740×1017 W. Is that per min, hour, day? Please, this would help greatly. 75.60.172.81 00:38, 15 November 2007 (UTC)

W is watts, that is joules per second. Han-Kwang (t) 00:47, 15 November 2007 (UTC)

...1366...?

How convenient that my comments were lost in the merger:
Once again, where is the specific reference for this specific (phony) value...1366 W/m²
I am not siting this as a better reference, just pointing out the discrepancy: ["1367.8204W/m²"]
GabrielVelasquez (talk) 06:36, 5 January 2008 (UTC)

You don't state what you're doing in those calculations. Are you calculating how much energy the Sun is emitting across its disk and then the fraction of that energy which the Earth intercepts? Are you accounting for how much energy is blocked by passing at various angles through the Sun's photosphere and corona? The energy absorbed by solar wind particles? There are undoubtedly other unknown factors. Is the number which you disagree with based upon theoretical calculations or measurements at the Earth? Measurements are more likely to include unknown factors and correspond better to reality. -- SEWilco (talk) 16:53, 5 January 2008 (UTC)

I find it cute when people miss the point (airplane sound overhead). Here, I'll copy this over from Talk:Insolation, and I hope it helps. Also you counter measurements with measurements, those are the calculations of professional scientist, I just did a little basic algebra.GabrielVelasquez (talk) 20:46, 5 January 2008 (UTC)

The reference is right there in the article (ref. 1), and pertains to measurements made during the last three solar cycles. An average value of 1366 units (to the nearest whole number) is clearly visible in the concluding graphs (Figures 4 and 5). I think you are preserving more decimal places in your results, and possibly attaching more importance to those extra digits, than is justified by the accuracy of the observational data. The value for R, for example, has only three significant figures (without taking into account the uncertainty of the measurement, which may degrade the accuracy further).

In the solar constant article, it says roughly 1366 W/m², and I am going to add the same word to this article. I hope this response helps. Hertz1888 (talk) 05:06, 2 January 2008 (UTC)

My-god-man, I almost needed a magnifying glass for that. And you had to actually point it out. Couldn't you place that "figure 4 and 5" below with/next-to the link for that article. And incidentally, why are you rounding up? - Just kidding.
I did shift the [1] over to the number itself.
thanks, GabrielVelasquez (talk) 07:01, 5 January 2008 (UTC)

Look at the Solar variation article, in particular the graph there. You see that it varies from about 1365.5 to about 1366.5, if you use the smoothed values; or rather more if you take the instantaneous values. Your error is to assume that your value for the sfc T of the sun is accurate. Try seeing how much you need to vary it to get down to 1365.5 - I would guess its very little. Oh,a nd I should also add that the graph is a bit misleading, because its a patchwork of different satellites, and their absolute calibration is a problem William M. Connolley (talk) 20:52, 5 January 2008 (UTC)

Ummm, the effective temperature of the sun is a derived number based on measuring the solar constant, not the other way around. If you want a highly accurate solar constant, then using a derived temperature without any specified source or uncertainty is not the way to go about it. Dragons flight (talk) 21:20, 5 January 2008 (UTC)

Ooowah, point taken: I know this isn't the place to ask this, but since you seem to know, I'm not still wrong in calculating HZ median Solar Constant distances for other stars with that formula?? f=(R²aT⁴)/(d²), from L=4π·R²aT⁴, and L=4π·d²f.
GabrielVelasquez (talk) 22:05, 5 January 2008 (UTC)

Terrible graphs

The article has three graphs, all of them different. We start with one of rather high detail but low quality; it uses the term "wavenumber" and other language that makes me think it was converted from another language. The next graph clearly states it is inaccurate, yet it has a rather prominent location in the article. Finally the third graph seems to be clear, and readable, yet uses a different set of axes that makes comparison difficult.

Surely we can do better?

Maury (talk) 15:16, 28 January 2008 (UTC)

Agreed. Anyone willing to have a go? Think outside the box 17:20, 1 February 2008 (UTC)

Loaded Sentence

"When ultraviolet radiation is not absorbed by the atmosphere or other protective coating, it can cause a change in human skin pigmentation."

A much more scientifically concise and accurate approach would be:

"When ultraviolet radiation is absorbed by the skin it can cause changes in pigmentation (relevant link). Various factors (duration of exposure, column ozone, air quality, weather, season, latitude, clothing, and other protective measures [with links where relevant]) affect actual solar ultraviolet exposure to the skin."

This, of course, assumes that a discussion of skin pigmentation belongs here.

Also - solar radiation is *white* to our eyes. Buy a yellow bulb, switch it on in and otherwise dark room and look at a white peice of paper - you will see the color yellow. Take that same peice of white paper out into direct sunlight - the paper will appear *white* not yellow. The solar spectrum at the surface is nearly flat from 450 nm to 650 nm and in the strictest sense is actually a bit stronger in the green (to which our eyes are more sensitive) than the yellow, but since our eyes are logarithmic detectors these subtle variations are not distinguishable. Sunlight is "white".

65.202.227.93 (talk)mjd 2008.04.11.10:28EDT —Preceding comment was added at 14:29, 11 April 2008 (UTC)

Solar radiation really is white. I didn't make that up. There is a common misconception that it is yellow due to two equally deceptive phenomena. The first, everyone tells you it's yellow - so you are predisposed to think so. Few ever actually try to stare at the sun to figure out what color it is for themselves (kids, don't try this - looking directly at the sun is bad for your eyes - that's why one should intuit the sun's color from the color it casts on a white object - which is white). Second, even if you try to take a look for yourself, looking at a dazzlingly white object on a very deep purple-blue (anti-yellow-orange) background can give the impression of a yellowish sun if the observation isn't carefully made. The sun really is white. —Preceding unsigned comment added by 207.59.146.178 (talk) 02:44, 23 April 2008 (UTC)

93 lumens of illumination per watt

"Direct sunlight gives about 93 lumens of illumination per watt of electromagnetic power, including infrared, visible, and ultra-violet. This compares with the best fluorescent lights."

This is a very confused/confusing paragraph, perhaps accreted from various contributors. If the first sentence is true, it is a very technical matter, having to do with the spectrum of the light and the way the human eye responds. (This is *not* a measure of the sun's efficiency at turning energy into light.) (See Photometry (optics) and Luminosity function.) The second sentence would appear to reference the production of light from electricity, technically a quite different -- there are no comparable numbers to compare here! I am going to remove the second sentence.-69.87.203.17 20:22, 27 May 2007 (UTC)

Spectrum of blue sky

"Spectrum of blue sky clearly showing solar Fraunhofer lines and atmospheric water absorption band."

This is a terrible graphic [3] to include in a Sunlight article. It is either very wrong, or just very misleading in this context. It shows almost nothing past visible, perhaps because of sensor limitations. Half of sunlight is IR, and there is some UV down to 300 nm. Actually, the comments with the image acknowledge how poor this data set is -- I'll try to remove it. There are great full-spectrum plots at Solar radiation.-69.87.203.17 20:36, 27 May 2007 (UTC)

Article needs rewriting

Seriously. First sentence, "Sunlight is bright."? There are other moderately funny/weird things in the article further on. Mild vandalism, perhaps? I'd put a rewrite tag on it but I don't know how.GreenSprite 09:12, 7 September 2007 (UTC)

This sentence is almost insultingly obvious.

  "  This is usually during the hours known as day. "

And what brilliant astronomer discoveered this curious little theory? —Preceding unsigned comment added by 164.92.175.76 (talk) 16:06, 25 February 2008 (UTC)

"Calculation" paragraph

Greetings, I am reading the "Calculation" paragraph, and wondering if the formula is valid at "noon", and / or at the moment of the day when a meridian is facing the sun perpendicularly? Essentially I think the paragraph should mention at which time of the day is the formula valid.

I am also wondering whether "Eext" is the illuminance on "top" of the atmosphere, or on the Earth as if there was no atmosphere? Lastly, I wish a few possible values were given for "c" and "m" (and "Edn"), and that "e" was clarified as being Euler's constant, if that's indeed what it is. —Preceding unsigned comment added by Jfclemay (talk • contribs) 21:31, 4 May 2008 (UTC)

Correction, I just realized that the formula doesn't consider latitude or longitude, sorry. In which case I am wondering if the lux value "Eext" is the quantity of lumens reaching the Earth, divided by half the area of the Earth's sphere? —Preceding unsigned comment added by 82.45.130.213 (talk) 22:22, 4 May 2008 (UTC)

Pluto

Excuse me sirs, but if I'm not mistaken, since C 2006, pluto was classified as "dwarf planet". So, should we revise the table? If so, then I'd thank anyone who do it cause I don't know how. Thank you.

Frozenman89 (talk) 02:03, 15 September 2008 (UTC)

Well, the text above the table is quite clear on the subject: "A rough table comparing the amount of light received by each planet on the Solar System (and the dwarf planets Ceres and Pluto) follows". However now I fix the table column title. Thanks. --Cyclopia (talk) 06:36, 15 September 2008 (UTC)

Merge

Solar radiation covers the same ground as this article, and should be merged with it. Serendi^podous 18:25, 25 September 2008 (UTC)

Agree. The merge also would help to put the information now in sunlight in better shape. --Cyclopia (talk) 09:10, 26 September 2008 (UTC)

Merge completed. Serendi^podous 09:39, 26 September 2008 (UTC)

Thanks for flushing the maximum and minimum I had calculated for the Solar Radiation article based on the perihelion and aphelion distances of the planets to show the range of solar radiation at these bodies and in a readily usable figure (W/m^2)... Just a good two hours in the drain. Thanks a lot for the expediency in which you did that merge...Cairan (talk) 06:38, 20 October 2008 (UTC)

Are you saying that you want the original back? That's pretty easy. Serendi^podous 07:21, 20 October 2008 (UTC)

There. Done. Serendi^podous 07:23, 20 October 2008 (UTC)

Thanks for answering this concern. Cairan (talk) 21:55, 20 October 2008 (UTC)

Illumination

The article states that "Bright sunlight provides illumination of approximately 100,000 candella per square meter at the Earth's surface.". Candela per square meter is a unit of luminance, not illuminance. Illuminance is measured in lux, and full daylight is ~10000 lux. Totsugeki (talk) 14:25, 19 October 2008 (UTC)

Thanks. Fixed. This article needs a real going over. There needs to be an explanation of the origins of sunlight the Sun's core, as well as its journey from the core to the photosphere, and from the photosphere to Earth. Serendi^podous 14:33, 19 October 2008 (UTC)

I think it isn't fixed yet. The correct unit is lux, not candela per square meter. See also daylight: Brightest sunlight is 120,000 lux, or illuminance. Or see the luminance article: The sun has luminance of about 1.6×10^9 cd/m2 at noon User:joosteto 20:40 26 October 2009 (UTC)

"120 watts per square metre" in opening paragraph

Anyone else find this confusing?

" "yes i do"The World Meteorological Organization defines sunshine as direct irradiance from the Sun measured on the ground of at least 120 watts per square metre.[1] "

I have three problems with this: 1. The reference link doesn't work and I haven't been able to find the article. 2. To a casual reader it seems like average sunlight is about an order or magnitude less than its maximum for Earth (on a cloudless day). 3. It doesn't make much sense to me... at sun rise, sunset, during a solar eclipse or a very cloudy day does it mean that what I can see is not sunlight?TFJamMan (talk) 15:19, 17 October 2009 (UTC)

If the sun is not shining, you can't see sunshine. Sunlight and sunshine aren't the same. DOwenWilliams (talk) 03:21, 3 January 2011 (UTC) David Williams

Blackbody spectrum 5800 vs 5500 K

The graph File:Solar_Spectrum.png shows a blackbody spectrum for 5250 °C = 5523 K. This is pretty different from the 5800 K figure given in the text. Since most sources say something aroung 5700-5800 K (Sun says 5778 K), I think that the label in the graph (or even the curve) is wrong. However, I've testes it with the solar spectrum Excel file and added a blackbody curve to it (maybe I can upload a graph created with Gnuplot later). The IR side and the UV drop is indeed best fitted with a BB spectrum around 5500 K while the peak fits better to 5800 K. However, one has to apply an overall scaling factor for BB temperatures different from about 5800 K. Maybe, the solution is that the Sun isn't a true black body.--SiriusB (talk) 15:27, 25 February 2009 (UTC)

Yes, the issue is that the sun isn't a blackbody. Treating it as one (by integrating the total energy and defining a single equivalent blackbody temperature) tends to misfit the shape of the spectrum as you noted. That's why a slightly colder reference curve was used. Dragons flight (talk) 17:44, 25 February 2009 (UTC)

Ah, I remarked on this farther up in the talk page. Yes, the solar spectrum we see isn't a perfect blackbody, but the higher value, 5800 K, should be used. The reason is the Sun has numerous absorption lines across the entire spectrum, including in the near and far IR, which should make (almost all) the actual spectrum lie beneath B(lambda)(Tsun). It is the contribution of all those closely spaced absorbsion lines that make it look cooler than it actually is. Remember, beneath the surface of last scattering the sun really is an excellent approximation of a blackbody, and the approximation gets better the deeper you go. So, what's going on is wavelengths of light that don't correspond to transitions in any common element are able to travel through the sun's atmosphere more easily than ones corresponding to a transition in one of the common elements (e. g. an atomic line.) We see these as absorption lines because the sun is cooler closer to the surface (excluding the corona), and light at the wavelengths corresponding to atomic transitions will get absorbed by cooler gas above it. In other words, there *is* a true blackbody temperature of the sun; you have to look beneath the chromsophere to see it, and that temperature at the surface of tau=1 (surface of last scattering) is 5800 K or so.

There are also emission lines, from the hot corona, so you should see certain very specific wavelengths be brighter than the blackbody curve, but not for such a large region as the entire visible range, as shown in the graph with a Tsun of 5500 K. Assuming the data is good, and the graph is scaled correctly, using B(lambda)(5780 K) should produce a fit where the entire spectrum lies beneath the blackbody curve. The difference between the two is absorption by the chromosphere. —Preceding unsigned comment added by 128.146.238.241 (talk) 21:01, 30 June 2009 (UTC)

Sorry for interfering, I was probably wrong in my last edit. Thank you for correcting me. Dan Gluck (talk) 15:41, 14 July 2009 (UTC)

Forcing temperature

The Forcing temperature is stated for all the planets in a table. It states that the forcing temperature is lower for the Earth than for Mars. I strongly suspect this is wrong, after all Mars is further away from the sun. Infact, all of the stated temperatures seem terribly wrong. However,I dont know the correct values, so I leave with no changes. —Preceding unsigned comment added by 130.238.68.61 (talk) 14:25, 13 October 2009 (UTC)

Quibbles about opening paragraph

The opening paragraph contains a series of facts about sunlight which seem rather random disjointed. Perhaps a few of the key points could be rewritten as a single paragraph of text, and the other points could be distributed into other parts of the article, to achieve better "flow"? Just a thought. — Preceding unsigned comment added by 87.112.212.35 (talk) 22:15, 31 August 2011 (UTC)

The opening paragraph says:

Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.

1. Do we have any sources that say sunlight can mean all solar electromagnetic radiation? The only definitions I can find of "sunlight" say that it means "the light from the sun", and, per Light, this would seem to restrict it to visible light only.

2. The casual inclusion of the bolded term "solar radiation" is rather offputting. Normally one would expect bolded terms to be introduced as part of a definition, but here the term is chucked into a sentence with no obvious reason why it, rather than the previous "sunlight" is being used. The distintion, if any, should be explicitly stated. If there is supposed to be no distinction, then the article should start with "Sunlight, or solar radiation, is ...".

.... in my opinion.

86.160.213.101 (talk) 02:28, 9 August 2011 (UTC)

Reorganize

Article should be moved to Solar radiation. The term "sunlight" has terrestrial connotations, like sun tanning, sunstroke, sunburn; these relate to what we do with the electromagnetic radiation (EMR) like infrared once it reaches the earth's surface.

An article that focuses primarily (or exclusively) on EMR which the sun produces, is what we need here.

This will help us distinguish between EMR, currently covered in Solar variation, and Solar wind. --Uncle Ed (talk) 17:29, 1 February 2012 (UTC)

"Sunlight" applies as much to Mars, Venus, Mercury, Titan and any other planet. I don't see why the use is Earthcentric. Serendi^podous 17:38, 1 February 2012 (UTC)

Let's break up Sunlight into two parts:

1. Solar radiation - all electromagnetic radiation the sun gives off, no matter what wavelength
   • radio, electromagnetic waves with frequencies significantly below those of visible light.
   • infrared
   • visible light
   • ultraviolet
   • x-rays, etc.
2. Sunlight - just infrared, visible light, and UV - the stuff that warms you, lets you see, or tans your skin

This will be less jarring to the reader, in accordance with the principle of least astonisment.

Let's use Wikipedia:Summary style to guide us. It might be a bit trickier than the break-out of Ground Zero controversy from Park51, but that's a recent (and so far, uncontroversial) experience that could be an example.

I envision Solar radiation as more technical, and Sunlight as more reader-friendly. --Uncle Ed (talk) 21:04, 7 February 2012 (UTC)

Requested move

The following discussion is an archived discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section.

The result of the move request was: no consensus to move. Favonian (talk) 23:17, 16 February 2012 (UTC)

---

Sunlight → Solar radiation – Move Sunlight to solar radiation (which currently redirects back to Sunlight because as the dictionary says, the term sunlight refers specifically to the electromagnetic radiation (ER) which is visible to the human eye. We also speak of "invisible" sunlight such as the warming rays of infrared and the tanning rays of ultraviolet (UV). But wavelengths of solar radiation longer than infrared (or shorter than UV) aren't usually called "sunlight", even by scientists, are they? Sunlight should be about solar radiation which we can see by, which warms us, or which tans us (yes, and gives us skin cancer). Solar radiation should be the general article on all wavelengths of ER the sun emits. Very likely the best arrangement would be to have a section on "Sunlight" in the Solar radiation article. We can use WP:Summary style and link this small section to the larger Sunlight article. Uncle Ed (talk) 16:09, 9 February 2012 (UTC)

• Comment – so far your case is not convincing. Can you show evidence that "sunlight" is usually treated as a subtopic of "solar radiation", as opposed to the other way around? I think the current title seems OK, but I'll look at what you can show. Dicklyon (talk) 16:26, 10 February 2012 (UTC)
  • Light is defined as visible radiation, so I should think it's inherent in the definitions that sunlight is a subtopic of solar radiation. I tend to support Ed's proposal to refocus this article on all solar radiation. Powers ^T 20:02, 11 February 2012 (UTC)
    • Light is also commonly used to label all EM radiation, particularly, also IR and UV light, which are not visible. While radiation also adds non-EM radiation... like alpha particles... 70.24.247.54 (talk) 05:27, 12 February 2012 (UTC)
• Oppose "solar radiation" includes non-EM radiation. A new page should be started on the topic of all forms of solar radiation, such as neutrino radiation. 70.24.247.54 (talk) 05:28, 12 February 2012 (UTC)

The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

Solar radiation ≥ sunlight

Could someone please explain why "solar radiation" redirects here? Sure, sunlight is certainly solar radiation, but so are other phenomenon that I do not see covered here. I.e. "solar radiation" is a much wider term. I don't think we should move this article, but "solar radiation" should definitely not be treated as a synonym. A disambig page perhaps? Or a summary article? -- Director (talk) 13:20, 13 October 2012 (UTC)

See the discussion above. There was no consensus for a move (which I think was the correct decision), but that doesn't mean we can't start a solar radiation article and kill the redirect. Which is actually my preference, and I think I'm going to be bold and do it.

A big problem here (which also speaks in favor of two articles) is that neither sunlight nor solar radiation are well-defined terms. Very often UV is counted as part of sunlight, inasmuch as "light" in science is not always visible light (there are types of INvisible light, unless you want to argue that infrared light is not really light). Radiation has the same problem. EM radiation (EMR) is well-defined, but radiation in physics includes EMR and particle radiation, all of which the Sun emits. All of this must be noted in the two articles, sunlight, and solar radiation. Generally, solar radiation is a wider topic, but there is considerably overlap and some disjunction in the sense that solar radiation is sometimes used to describe ONLY solar particle radiation (solar wind plus neutrinos), none of which is light. So the answer is not so straightforward as to make solar radiation the primary topic and have sunlight entirely a subarticle. It's only MOSTLY a subarticle. SBHarris 18:19, 13 October 2012 (UTC)

So you're saying "solar radiation" refers to all forms of radiation emitted by the sun, but can sometimes refer ONLY to the sun's particle radiation? Correct? Do the sources ever use the term "solar radiation" to refer ONLY to "sunlight"? -- Director (talk) 19:19, 13 October 2012 (UTC)

Speaking as the person who merged the articles initially, the reason I did so was because they were exactly the same; Sunlight simply had more information. I would be in favour of a de-merge assuming a sharp distinction can be made in the two articles' respective coverage, and that article creep doesn't eventually make both articles the same again. Serendi^podous 19:24, 13 October 2012 (UTC)

I am merely pointing out that it is highly misleading to equate solar radiation with sunlight, seeing as how "sunlight" merely covers one type of solar radiation. If the articles had both covered only sunlight, it wasn't a mistake to merge them, but it does seem to be a mistake to have solar radiation redirect here. Especially if, as Sbharris says, the term can sometimes refer specifically to forms of solar radiation that are NOT sunlight.

From a logical perspective the terms are neither "sharply distinct" nor do they overlap. One term is simply wider and includes the other, like "vehicle" and "car". -- Director (talk) 19:49, 13 October 2012 (UTC)

I have to partly retract what I said about solar radiation. I've seen solar radiation refer to solar ionizing radiation (just as "radiation" is loosely sometimes used to speak of only ionizing radiation). In this sense it would cover the most highly energetic solar radiations: particles (but NOT neutrinos since they don't interact enough to cause significant ionization) PLUS the most energetic of EMR-- X-rays and the ionizing part of UV, which part is in the vacuum range for obvious reasons. But "sunlight" in any case is in no way a subset of "solar radiation" if that latter term is used in the sense of "solar ionizing radiation." It's only a subset if you want to define "solar radiation" in the most general terms that you can, which is all radiation of any type that leaves the Sun.

Anyway, I vote we create solar radiation and generally move every solar energy output class into it except visible light, non-ionizing UV, and (perhaps) infrared. We can reference each of these with one sentence, and discuss them more fully here.

Note also that there are already articles on light (which on Wikipedia is used to discuss electromagnetic radiation in the visible spectrum), as well as good articles on ultraviolet and infrared. Sunlight should not repeat that stuff, and indeed the part on solar visible light in light (which also covers artificial visible illumination, starlight, and so on) should mostly be moved here, and mentioned in light only as a small section, with sunlight as its main article, per WP:SS.

This article on sunlight might have a section on raw sunlight, which is the visible/IR/UV you encounter in space, and then a longer section on sunlight as it appears on Earth, which should really have stuff about lumens, quality measurements, art, aesthetics, and stuff that is sometimes softer science than light (which of course covers visible light from sources other than the Sun as well). Don't you think? Some of that has been suggest above, and I agree. SBHarris 20:04, 13 October 2012 (UTC)

The way I'd do it is I'd have an overview article with "main article:" links to every form of radiation the sun emits (e.g "Main article: Solar wind" and "Sunlight"). Unless of course there is a clear consensus in the sources for "solar radiation" referring to a specific type of radiation. IMO it's safe to say "solar radiation" usually means "solar radiation" ie radiation emitted by the sun, any and all. -- Director (talk) 22:47, 13 October 2012 (UTC)

I think I agree. Do you want to bite the bullet and create the solar radiation article and stick an {{under contruction}} tag on it while we move stuff to it and write for it and make main article links in it? SBHarris 02:06, 26 October 2012 (UTC)

Black body discrepancy

It's not clear from the article why the article says that the sun emits as a black body around 5800K but the diagram says 5250 degrees C. Richard Clegg (talk) 12:09, 24 December 2012 (UTC)

Redundancy between sections “Solar constant” and “Total (TSI) and spectral solar irradiance (SSI) upon Earth”, need for definitions, other articles

The two sections “Solar constant” and “Total (TSI) and spectral solar irradiance (SSI) upon Earth” display a lot of redundancy — I have the impression the latter was added without checking the article as a whole. It could not find a definition of TSI, so I added one here, but I am not sure how to define SSI, although that is needed to. I imagine it might be “the amount of solar radiation of a given frequency entering the atmosphere”, or something about “per frequency” but am not confident enough about how that is used. I have also seen talk of “secular solar irradiation”, which I presume is about long-term variation, and should presumably also be described somewhere and added to Secular (disambiguation). I realise there is a discussion on how to organise this information, and this seems a part of it.

I have made the disambiguation page TSI refer to Total Solar Irradiance (should perhaps not be all capitals?), and that to redirect to an anchor of the same name in the latter section, but now wonder if that was such a good idea. Perhaps it would be better to move this information to solar constant, or the proposed solar radiation. I am very much in favour of splitting the scientific information in sunlight (or sunshine) from the cultural, in solar radiation. The cultural aspects got rather short shrift in the previous discussions, and are very scantily treated in this article – perhaps a nerd bias in Wikipedia? The article solar variation is also of interest in any reorganisation, and perhaps the category Category:solar phenomena --PJTraill (talk) 18:09, 31 December 2012 (UTC)

Spectrum?

It would be nice to have picture showing the spectrum as seen thru a prism, accompanied by an intensity graph, for both the actual spectrum of the Sun and the spectrum as seen at sea level on Earth. --TiagoTiago (talk) 07:27, 4 June 2013 (UTC)

Gamma rays

While the gamma rays created through fusion in the core do not make it out to the photosphere, the Sun does occasionally emit gamma rays during solar flares (as observed by RHESSI and Fermi), and it does emit a small background of gamma rays resulting from cosmic rays impacting the photosphere (as observed by Fermi). Spacehippy (talk) 17:39, 5 December 2013 (UTC)

Atmospheric filter

I agree with the value of spectranalysis. Is it coincidence that the sky away from the sun looks light blue and the difference between the visible [solar spectrum] above & below the atmosphere is somewhat greater in blue? My intuition (for what it is worth) says that light blue implies broad spectrum (white) with an excess of blue produces a light blue. On a possibly related issue, is some 'average' of the yellow sun and the blue sky (maybe plant green too), a basis for our evolved perception of white?
--Wikidity (talk) 23:36, 23 March 2014 (UTC)

Sunbathing bla bla

Totally off-topic imho:

"Women often try to shift or remove clothing straps from areas that would be exposed by a different style of clothing. This means the area gets some tan and strap marks are not too obvious. One way this is done is to remove straps while lying face down, so as to avoid being seen topless. Another way is to adjust the straps slightly a few times while tanning."

I would simply delete the section. The text before and after this paragraph isn't much better. — Preceding unsigned comment added by 80.187.108.19 (talk) 15:18, 6 May 2014 (UTC)

Summary

I don't see why "A photon starting at the centre of the sun and changing direction every time it encounters a charged particle would take between 10 000 and 170 000 years to get to the surface." should be stated so early. That is not actually a significant part of the process by with sunlight is generated.

It's not even a meaningful part. Photons are just packets of electromagnetic energy obeying Bose-Einstein statistics and as such don't have identities. Particles absorb and emit photons but an emitted photon can't be identified with any specific absorbed photon; if it could it would obey Fermi-Dirac statistics. Putting this sentence right after the 8.3 minutes for sunlight to reach Earth implies an impossibly slow flow of energy from the center of the Sun to the surface. Vaughan Pratt (talk) 06:32, 27 July 2014 (UTC)

'Life on Earth' Section

At the end of the section, "peak oil" and "new urbanism" are given as examples of possible post-fossil-fuel scenarios. Both are in fact irrelevant examples regarding the topic. — Preceding unsigned comment added by 205.211.133.128 (talk) 13:43, 3 March 2015 (UTC)

Semi-protected edit request on 24 January 2016

Under the Heading "Calculations" the sentence which begins "where dn=1 on January 1; dn=2 on January 2; dn=32 on February 1,..." should read "...dn=3 on February 1..." Francis newman welder (talk) 13:11, 24 January 2016 (UTC)

Done --allthefoxes ^(Talk) 16:49, 24 January 2016 (UTC)

Spectral composition of sunlight at Earth's surface

The graph displayed as of 5/18/16 for the spectral composition at earth's surface needs improvement. Some of the lines are nearly invisible. A better explanation of the chart is also needed. It appears that ~460nm was chosen to yield an equal hight peak on the image and all spectra scaled to obtain this result, I assume this was to illustrate the relative composition of the light shifting. That rescaling and the reasoning behind it should be mentioned in the text. I think this motivation does justify the rescaling. If possible I'd like to see the intensity difference in a second plot. The 'x1.2, x16, x1.3...'. in the key on this plot gives a quantitative feel of the intensity differences, but the visual differences in an unscaled graph would convey it better to those who are less concerned about the exact number. However, having two graphs might take up too much space on the page. So perhaps the only change needed is better labeling and a better color scheme of the current graph. — Preceding unsigned comment added by 169.234.17.24 (talk) 19:47, 19 May 2016 (UTC)

Calculating lumens per square meter in summary section

In the summary section, it state's that the direct sunlight at the Earth's surface is 1050 W/m2. It is also stated that sunlight includes the infrared, visible, and ultraviolet bands. The summary section then multiplies 1050 W/m2 by 93 lumens per watt to get a value. However, lumens is a measure that pertains only to visible light; is it appropriate to multiply it by 1050 W/m2 when that value represents more than just visible light? — Preceding unsigned comment added by 70.171.18.164 (talk) 00:19, 2 January 2017 (UTC)

Answer for ‎Toddst1‎

Todd the reversal was not made on 'your' edit, but the one 'after' your edit. There are a number of us chasing this guy: User:Hemant banswal‎ around the site, who keeps changing the opening photos on articles. All I did here was revert him, and warn him to stop. I hope that explains your question. Thanks - Pocketthis (talk) 21:28, 3 January 2017 (UTC)

• P.S. I am in a hurry to make an appointment right now, and am messing up my post to you Toddst1. Perhaps if you go to his talk page and see the countless warnings, with no reply or adherence from him at all, it will explain my "over the top" edit summary. I even left him a friendly advice message this morning, however, this kid keeps on truck'in, and that's that. I may have overdone my edit summary, but at this point I wanted to see if I could jolt some sense into him. Trust me, that is not like any edit summary I have ever left before :-) Pocketthis (talk) 21:56, 3 January 2017 (UTC)

Thanks. I appreciate the response. It sounds like WP:ANI might be in order. Toddst1 (talk) 22:41, 3 January 2017 (UTC)

direct vs indirect sunlight.

I made an anchor for direct sunlight to redirect here, i note there is also direct insolation and the constrasting concept of diffuse solar radiation (Diffuse sky radiation) which has it's own page. Could there be a subheading here which mentions these contrasting concepts, perhaps MfortyoneA (talk) 18:24, 2 March 2017 (UTC)

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Intensity in the Solar System

The caption for the Martian sunset bothers me. The image itself does not show that "Sunlight on Mars is dimmer than on Earth." The brightness of the image is largely determined by the exposure time, aperture, ISO of the camera, as well as local atmospheric conditions and time of "day". In this particular image, the sun is overexposed (according to the image's description page) so on Earth or on Mercury the camera would record the same (maximum) brightness. Of course, it is true that sunlight on Mars is dimmer than on Earth, but this photo is not good evidence of that fact. The image does claim to accurately represent the colours in the sky, so perhaps the caption could be changed to reflect that? Maybe: "A photo of a Martian sunset taken by the Mars Pathfinder shows how red light is scattered due to the dust in the Martian atmosphere." Chris.rapson (talk) 03:15, 15 January 2019 (UTC)

Contradiction regarding visibile vs infrared light reaching the ground

At one point the article says, "sunlight at Earth's surface is 52 to 55% infrared." Later the article says, "The Sun's electromagnetic radiation which is received at the Earth's surface is predominantly light that falls within the range of wavelengths to which the visual systems of the animals that inhabit Earth's surface are sensitive." I don't know how to resolve that contradiction. I also note that the first statement is based on the editor's own otherwise unpublished calculations and the second statement is not sourced at all. — Preceding unsigned comment added by 2601:646:C200:74B4:78E8:F3A7:3550:1BC3 (talk) 23:45, 16 April 2019 (UTC)

I resolved the contradiction

The section entitled Spectral composition of sunlight at Earth's surface was modified by eliminating the first sentence that contradicted an earlier statement in the article and eliminated the word "therefore" from the second sentence. — Preceding unsigned comment added by 2601:646:C200:74B4:18F5:B395:D10E:1A2D (talk) 15:16, 24 April 2019 (UTC)

Time it takes for a photon to reach the solar surface

Suggestion to get rid of the current third paragraph:

"Sunlight takes about 8.3 minutes to reach Earth from the surface of the Sun. A photon starting at the center of the Sun and changing direction every time it encounters a charged particle would take between 10,000 and 170,000 years to get to the surface.[3]"

This may be a misleading claim (see, e.g., here: https://twitter.com/mickeykats/status/1137837176643883012) and should at the very least be featured less prominently — Preceding unsigned comment added by 96.41.230.164 (talk) 03:29, 10 June 2019 (UTC)

Solar spectrum x-axis: add frequency?

--80.253.94.253 (talk) 07:20, 14 June 2019 (UTC)