<p>There are many references about this on the web, such as <a href="https://en.wikipedia.org/wiki/Sunset">Wikipedia</a> and the <a href="http://www.spc.noaa.gov/publications/corfidi/sunset/">NOAA</a> site.</p>

<p>At sunrise and sunset the angle the Sun's light makes with the Earth at those locations is low compared with angle the light makes at midday. Because of the low angle, the light has to travel through more of the atmosphere before it reaches the Earth's surface and the eyes of anyone watching either the Sun rise or the Sun set.</p>

<p>The colour of the Sun's light is white, being composed of the colours of the light spectrum: red, orange, yellow, green, blue, indigo and violet. The <a href="http://science-edu.larc.nasa.gov/EDDOCS/Wavelengths_for_Colors.html">wavelength</a> of these component colours are all different. Red has the longest wavelength at 650 nm. Each of the other colours have shorter wavelengths with violet having the shortest at 400 nm.</p>

<p>As the Sun's light passes through the atmosphere it get scattered by the air molecules and particles in the air such as dust and aerosols. </p>

<p>Due to a phenomenon known as <a href="https://en.wikipedia.org/wiki/Rayleigh_scattering">Rayleigh scattering</a> the shorter wavelengths of light (greens, blues, violets) are scattered first, leaving the shorter wavelengths (yellows, oranges and reds) to travel further.</p>

<p>The greater the amount of particles in the air, dust and aerosols, the greater the degree of scattering and the more red the sunrises and sunsets will appear. This is particularly evident after large amounts of ash have been ejected by <a href="http://www.livescience.com/12834-iceland-volcano-fiery-sunsets.html">volcanoes</a>, after large forest fires and in locations where <a href="http://www.economist.com/blogs/babbage/2014/04/air-pollution">air pollution</a>, particularly from industrial chimney stacks and internal combustion engines from road vehicles is a major source of airborne <a href="http://www.scientificamerican.com/article/fact-or-fiction-smog-creates-beautiful-sunsets/">particulate</a> matter such as soot or ash and other very small products of combustion</p>

CC BY-SA 3.0
2015-09-28T19:48:45.640Z
@Ian during the day the sky is blue because only the short blue and violet wavelengths are appreciably scattered out of the beam of sunlight.  As the optical path length increases at sunset the longer wavelengths scatter out of the beam.  There is only so much "blue" to be had and much more "yellow" (the sun's peak wavelength).  When more colors are being scattered you see the sum of that light, so the turn from blue to warmer colors.  Additionally, if there are clouds you often see those directly illuminated by the remaining red/pink/orange colors left in the solar beam.
casey
CC BY-SA 3.0
2015-10-06T08:40:38.693Z
I love this picture as the visual is easy to understand.   http://math.ucr.edu/home/baez/physics/General/BlueSky/blue_sky.gif     Source:   http://math.ucr.edu/home/baez/physics/General/BlueSky/blue_sky.html   Also, Ian, the scattering of blue light turns the sun slightly redder, giving it, it's familiar yellow color in the sky.   If we had no atmosphere, the sun would appear pure white.
userLTK
CC BY-SA 3.0
2017-04-18T13:47:50.533Z
[Tyndall's Sky In A Box Experiment w/ Brian Cox](https://www.youtube.com/watch?v=JI3kH-3TiKQ)
Jan Doggen
CC BY-SA 3.0
2015-04-25T02:35:19.460Z
2015-04-25T02:35:19.460Z
Fred
<p>What causes the typical red, pink or orange colors seen in sun-rises and sun-sets?</p>

<p>How come the sky doesn't just turn a darker blue?</p>

CC BY-SA 3.0
2015-04-24T16:07:05.813Z
This question is to emphasize my point in my answer to this meta post: http://meta.earthscience.stackexchange.com/questions/1436/lets-get-critical-apr-2015-site-self-evaluation  about how we need some simpler questions on the site to attract more new users.
Azzie Rogers
CC BY-SA 3.0
2015-04-24T17:30:26.650Z
Just for cross-ref: this is close to being a duplicate of [Golden and red colored light even after sunset](http://earthscience.stackexchange.com/questions/970/golden-and-red-colored-light-even-after-sunset). There are also [one](http://physics.stackexchange.com/questions/99745/why-does-the-sun-turn-red-near-sunset) [two](http://physics.stackexchange.com/questions/126847/why-isnt-the-sunset-sunrise-rainbow-colored) [three](http://physics.stackexchange.com/questions/137189/why-is-the-sky-never-green-it-can-be-blue-or-orange-and-green-is-in-between) similar/related questions over on Physics SE.
Matt Hall
CC BY-SA 3.0
2015-04-24T18:33:35.037Z
@kwinkunks Yep, it would seem so.  I wouldn't have asked this if I had seen that one in the list of 'Questions that may already have your answer'... Do you think they're close enough that this one should be deleted?
Azzie Rogers
CC BY-SA 3.0
2015-04-24T20:08:18.877Z
As-is, I think they probably are too similar, yes. I'm not very up on the policies there though.
Matt Hall
CC BY-SA 3.0
2015-04-24T21:05:46.633Z
@kwinkunks: As is, in my opinion, this question is not a duplicate of the question linked to above.  If it is, then the first question would need to be edited to cover the scope of this question without changing the intent of the question or somehow expanding the scope of the question to make the current answers less useful or worse, invalid. If have questions about my position, let me know. Thanks.
blunders
<atmosphere><light>
What causes the colors seen during a sunset / sunrise?
Azzie Rogers
# What causes the colors seen during a sunset / sunrise?

(Asked by: username_0 on 2015-04-24)

What causes the typical red, pink or orange colors seen in sun-rises and sun-sets?

How come the sky doesn't just turn a darker blue?

**Tags:** atmosphere, light

> **Comments:**
> **username_0**: This question is to emphasize my point in my answer to this meta post: http://meta.earthscience.stackexchange.com/questions/1436/lets-get-critical-apr-2015-site-self-evaluation  about how we need some simpler questions on the site to attract more new users.  
> **username_1**: Just for cross-ref: this is close to being a duplicate of [Golden and red colored light even after sunset](http://earthscience.stackexchange.com/questions/970/golden-and-red-colored-light-even-after-sunset). There are also [one](http://physics.stackexchange.com/questions/99745/why-does-the-sun-turn-red-near-sunset) [two](http://physics.stackexchange.com/questions/126847/why-isnt-the-sunset-sunrise-rainbow-colored) [three](http://physics.stackexchange.com/questions/137189/why-is-the-sky-never-green-it-can-be-blue-or-orange-and-green-is-in-between) similar/related questions over on Physics SE.  
> **username_0**: @kwinkunks Yep, it would seem so.  I wouldn't have asked this if I had seen that one in the list of 'Questions that may already have your answer'... Do you think they're close enough that this one should be deleted?  
> **username_1**: As-is, I think they probably are too similar, yes. I'm not very up on the policies there though.  
> **username_2**: @kwinkunks: As is, in my opinion, this question is not a duplicate of the question linked to above.  If it is, then the first question would need to be edited to cover the scope of this question without changing the intent of the question or somehow expanding the scope of the question to make the current answers less useful or worse, invalid. If have questions about my position, let me know. Thanks.  

---

## 1 answers

### Answer by username_3 on 2015-04-25. Score: 9 | Accepted answer

There are many references about this on the web, such as [Wikipedia](https://en.wikipedia.org/wiki/Sunset) and the [NOAA](http://www.spc.noaa.gov/publications/corfidi/sunset/) site.

At sunrise and sunset the angle the Sun's light makes with the Earth at those locations is low compared with angle the light makes at midday. Because of the low angle, the light has to travel through more of the atmosphere before it reaches the Earth's surface and the eyes of anyone watching either the Sun rise or the Sun set.

The colour of the Sun's light is white, being composed of the colours of the light spectrum: red, orange, yellow, green, blue, indigo and violet. The [wavelength](http://science-edu.larc.nasa.gov/EDDOCS/Wavelengths_for_Colors.html) of these component colours are all different. Red has the longest wavelength at 650 nm. Each of the other colours have shorter wavelengths with violet having the shortest at 400 nm.

As the Sun's light passes through the atmosphere it get scattered by the air molecules and particles in the air such as dust and aerosols.

Due to a phenomenon known as [Rayleigh scattering](https://en.wikipedia.org/wiki/Rayleigh_scattering) the shorter wavelengths of light (greens, blues, violets) are scattered first, leaving the shorter wavelengths (yellows, oranges and reds) to travel further.

The greater the amount of particles in the air, dust and aerosols, the greater the degree of scattering and the more red the sunrises and sunsets will appear. This is particularly evident after large amounts of ash have been ejected by [volcanoes](http://www.livescience.com/12834-iceland-volcano-fiery-sunsets.html), after large forest fires and in locations where [air pollution](http://www.economist.com/blogs/babbage/2014/04/air-pollution), particularly from industrial chimney stacks and internal combustion engines from road vehicles is a major source of airborne [particulate](http://www.scientificamerican.com/article/fact-or-fiction-smog-creates-beautiful-sunsets/) matter such as soot or ash and other very small products of combustion

> **Comments:**
> **username_4**: @Ian during the day the sky is blue because only the short blue and violet wavelengths are appreciably scattered out of the beam of sunlight.  As the optical path length increases at sunset the longer wavelengths scatter out of the beam.  There is only so much "blue" to be had and much more "yellow" (the sun's peak wavelength).  When more colors are being scattered you see the sum of that light, so the turn from blue to warmer colors.  Additionally, if there are clouds you often see those directly illuminated by the remaining red/pink/orange colors left in the solar beam.  
> **username_5**: I love this picture as the visual is easy to understand.   http://math.ucr.edu/home/baez/physics/General/BlueSky/blue_sky.gif     Source:   http://math.ucr.edu/home/baez/physics/General/BlueSky/blue_sky.html   Also, Ian, the scattering of blue light turns the sun slightly redder, giving it, it's familiar yellow color in the sky.   If we had no atmosphere, the sun would appear pure white.  
> **username_6**: [Tyndall's Sky In A Box Experiment w/ Brian Cox](https://www.youtube.com/watch?v=JI3kH-3TiKQ)  

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