# When is there stronger sunlight? **URL:** \ **Category:** Factual Questions\ **Created:** [July 9, 2014, 3:39am UTC](https://boards.straightdope.com/t/when-is-there-stronger-sunlight/692692 "2014-07-09T03:39:24Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![boffking](https://avatars.discourse-cdn.com/v4/letter/b/858c86/32.png) [@boffking](https://boards.straightdope.com/u/boffking)\ **Post date:** [July 9, 2014, 3:39am UTC](https://boards.straightdope.com/t/when-is-there-stronger-sunlight/692692/1 "2014-07-09T03:39:24Z")
People often say that the strongest sunlight is around the summer solstice. However, it is also painfully bright on a clear winter day with fresh snow on the ground. Which one is actually stronger/brighter? ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [July 9, 2014, 3:47am UTC](https://boards.straightdope.com/t/when-is-there-stronger-sunlight/692692/2 "2014-07-09T03:47:33Z")
> [@boffking](#): > > it is also painfully bright on a clear winter day with fresh snow on the ground. Snow can certainly reflect light, but you’d have to torture meanings rather harshly to argue that snow makes sunlight stronger. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [July 9, 2014, 4:05am UTC](https://boards.straightdope.com/t/when-is-there-stronger-sunlight/692692/3 "2014-07-09T04:05:37Z")
bright sunlight reflected off snow for long periods can burn the eyes due to the UV light. ---
**Author:** ![standingwave](https://avatars.discourse-cdn.com/v4/letter/s/9de0a6/32.png) [@standingwave](https://boards.straightdope.com/u/standingwave)\ **Post date:** [July 9, 2014, 4:27am UTC](https://boards.straightdope.com/t/when-is-there-stronger-sunlight/692692/4 "2014-07-09T04:27:55Z")
> [@johnpost](#): > > bright sunlight reflected off snow for long periods can burn the eyes due to the UV light. It can also burn the roof of one’s mouth as I’ve learned climbing glaciers on Mt Rainier. ---
**Author:** ![chacoguy](https://avatars.discourse-cdn.com/v4/letter/c/50afbb/32.png) [@chacoguy](https://boards.straightdope.com/u/chacoguy)\ **Post date:** [July 9, 2014, 4:31am UTC](https://boards.straightdope.com/t/when-is-there-stronger-sunlight/692692/5 "2014-07-09T04:31:48Z")
That’s it right there. Clear skies at high altitude. Using the light meter on my camera, I found that the sun is about eight times brighter in Moab, Utah than it is in Lincoln Nebraska. ---
**Author:** ![Ornery\_Bob](https://avatars.discourse-cdn.com/v4/letter/o/da6949/32.png) [@Ornery\_Bob](https://boards.straightdope.com/u/Ornery_Bob)\ **Post date:** [July 9, 2014, 4:33am UTC](https://boards.straightdope.com/t/when-is-there-stronger-sunlight/692692/6 "2014-07-09T04:33:23Z")
It depends on what you mean by “stronger” and how you want to measure it. If you look directly at the sun, it’s painfully bright. If you look down at the ground, it’s not. Same sun, same brightness, different results not because of any difference in the sunlight, but simply due to how much of it is getting into your eyes. Summer day vs. snow day… same sun, same brightness, different results because more reflected light is getting into your eyes. I think the “strength” of light in the sense you really mean is determined by the distance from the source and the angle of incidence. ---
**Author:** ![filmstar-en](https://avatars.discourse-cdn.com/v4/letter/f/50afbb/32.png) [@filmstar-en](https://boards.straightdope.com/u/filmstar-en)\ **Post date:** [July 9, 2014, 9:06am UTC](https://boards.straightdope.com/t/when-is-there-stronger-sunlight/692692/7 "2014-07-09T09:06:41Z")
What is stronger sunlight? If you mean the narrow range of frequencies detected by human eye or that effects the skin. This is not to be confused with the amount of energy falling per metre. This is most likely at the equator when the sun is directly overhead. You will get more energy when there is less atmosphere to absorb it. So, at the top of mountains. But then light can come from two main sources. Direct from the sun and reflected by objects in the environment. So being surrounded by a white reflective landscape. At the summer solstice, at mid day. Surrounded by snow on a mountain at the equator…🆒 I would vote for Kilimanjaro in Africa. [http://www.mtkilimanjarologue.com/gear/dont-forget-sunblock-and-sunglasses.html](http://www.mtkilimanjarologue.com/gear/dont-forget-sunblock-and-sunglasses.html) ---
**Author:** ![Iggy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/iggy/32/3364_2.png) [@Iggy](https://boards.straightdope.com/u/Iggy)\ **Post date:** [July 9, 2014, 10:18am UTC](https://boards.straightdope.com/t/when-is-there-stronger-sunlight/692692/8 "2014-07-09T10:18:52Z")
Add in that the Earth is slightly closer to the sun during the Northern Hemisphere winter then… perhaps a high altitude location along the Tropic of Capricorn around the N.H. winter solstice? Someplace in the Andes mountains, perhaps [Llullaillaco](http://en.wikipedia.org/wiki/Llullaillaco)? ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [July 9, 2014, 11:42am UTC](https://boards.straightdope.com/t/when-is-there-stronger-sunlight/692692/9 "2014-07-09T11:42:57Z")
> [@chacoguy](#): > > That’s it right there. Clear skies at high altitude. Using the light meter on my camera, I found that the sun is about eight times brighter in Moab, Utah than it is in Lincoln Nebraska. “eight times brighter” beggars belief, unless you were measuring something other than the direct radiation from the sun itself. A few thousand feet of air might make things a _little_ dimmer in Lincoln than in Moab, but not by a factor of 8. To the OP, yes, one would expect that at the moment the sun is most directly overhead, it’s passing through the atmosphere on the shortest path possible, and therefore has the highest intensity when it reaches your eyeballs. A more reflective environment (e.g. fresh snow cover) will reflect photons toward you that otherwise would not have hit you. So of these two scenarios: A) summer solstice in a grassy meadow B) winter solstice in a snow-covered meadow in scenario B), it may be possible to have more total light reaching your eyeballs, even though the flux arriving directly from the sun itself on your eyeballs is less than in scenario A). ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [July 9, 2014, 11:57am UTC](https://boards.straightdope.com/t/when-is-there-stronger-sunlight/692692/10 "2014-07-09T11:57:17Z")
> [@filmstar-en](#): > > I would vote for Kilimanjaro in Africa. Quito, Ecuador … 0º15’S @ 2,850 meters elevation … and there’s a airport. Oh, you don’t mind climbing, there’s a place right near by … ---
**Author:** ![Nava](https://avatars.discourse-cdn.com/v4/letter/n/da6949/32.png) [@Nava](https://boards.straightdope.com/u/Nava)\ **Post date:** [July 9, 2014, 12:15pm UTC](https://boards.straightdope.com/t/when-is-there-stronger-sunlight/692692/11 "2014-07-09T12:15:53Z")
Doesn’t snow, though; Kilimanjaro’s snows are disappearing but still there. ---
**Author:** ![pulykamell](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pulykamell/32/3166_2.png) [@pulykamell](https://boards.straightdope.com/u/pulykamell)\ **Post date:** [July 9, 2014, 3:14pm UTC](https://boards.straightdope.com/t/when-is-there-stronger-sunlight/692692/12 "2014-07-09T15:14:35Z")
> [@Machine\_Elf](#): > > “eight times brighter” beggars belief, unless you were measuring something other than the direct radiation from the sun itself. A few thousand feet of air might make things a _little_ dimmer in Lincoln than in Moab, but not by a factor of 8. Yeah, that sounds pretty astounding to me. That’s a 3 stop difference in photo terms. I’ve never noticed there to be that much variation on the “sunny 16” rule, even at high altitudes. Maybe a third to two-thirds of a stop, but no way 3 stops. A post [here recounts a photographer in the Andes](http://photo.net/bboard/q-and-a-fetch-msg?msg_id=001w3N), and he says “During extremely bright, mid-day conditions, the meter on the 6 (an averaging meter) was consistently giving me exposures of 1/125 at F16 using ASA 100 film (Provia 100F); i.e., it matched the “sunny F16” rule. It felt so much brighter than “sunny” days at sea level, that I didn’t trust the meter, and bracketed like crazy. The exposures, however, were dead on.” I should add, **chacoguy** , how are you metering? Are you metering off a known 18% gray reference point (or at least the same object, like the back of your hand)? It doesn’t sound like you’re using an incident meter (which would be another accurate way to do it.) Are you just doing an average reading of a sandy, desert scene vs a gray cityscape? ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [July 9, 2014, 6:41pm UTC](https://boards.straightdope.com/t/when-is-there-stronger-sunlight/692692/13 "2014-07-09T18:41:46Z")
> [@Nava](#): > > Doesn’t snow, though; Kilimanjaro’s snows are disappearing but still there. I’m only giving away 600 feet with [Antisana](http://en.wikipedia.org/wiki/Antisana), just 31 miles from Quito Airport. Lots of snow there. ---
**Author:** ![dstarfire](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dstarfire/32/5762_2.png) [@dstarfire](https://boards.straightdope.com/u/dstarfire)\ **Post date:** [July 10, 2014, 7:38pm UTC](https://boards.straightdope.com/t/when-is-there-stronger-sunlight/692692/14 "2014-07-10T19:38:34Z")
I understand “strongest sunlight” when/where/how (i.e. as the condition in which) the average amount\* of light striking an average sized\*\* person\*\*\* is greatest. As for wavelengths, I’d include the ultraviolet and infrared ranges since we can feel those (albeit over time, as sunburn, for UV). For locations, I’d limit it to within the earth’s atmosphere, or even just those places where a human can survive with only self-contained support apparatus (e.g. warm clothing, oxygen tanks), and reach without powered machinery (i.e. top of Mt. Everest would count, but an aircraft or balloon (even below Everest’s height) would not. \*to account for the the fact that some parts will get more light, some parts will get less \*\* Andre the Giant or Brad Williams would result in a non-representative sample \*\*\* I assume the OP is talking about light we can see or feel. If it doesn’t touch a person (whether directly, as a reflection (e.g. from snow or water), or due to scattering (e.g. seen in the sky)) we probably aren’t aware of it, outside a few specialized fields (of science, of study, of profession, etc). Dion Starfire, Technical to English translator