The Color of the Sky - UGS Project

8/10/2019 The Color of the Sky - UGS Project

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Christian Phan

UGS 302 - Living Color

Professor Nancy Kwallek

Final Project

Sunrise and Sunset: The Colors of the Sky

12.1.14


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When was the last time you really appreciated the brilliance a sunset? Often times we

are too self-occupied to even look at the sky when it happens, but I urge you pay

attention to the world around us. Because when the settings are just right, you will be

rewarded with the purest sensation of color that nature has to offer and if you really look,

you will see the vast influence on color that this ephemeral phenomenon is capable of. This

paper seeks to answer two main questions: 1) What are the colors of the sunset and why?

2) Is there a difference in color between sunrise and sunsets?

The Experiment

For subjective analysis, this study asked 20 participants to answer several questions

and to go observe both a sunrise and a sunset, describing their observations.

What color do you think sunrise and sunsets are? (before observing)

Is there a difference in color between the two? (after observing)

Being shown a number of sunrise/sunset pictures, can you tell which one is which?

(after observing)

The results of the questions were as follows:

Unanimously, all twenty participants described sunrises and sunsets to be red and/or

pinkish in hue

After taking the time to go observe both events, a majority (17/20) of the

participants noticed a change in color from the sunrise to the sunset.

The rest saw no difference in color (3/20)

Being presented with 6 images of half sunrise/half sunset, participants could only

describe what the correct event was with a 35.87% accuracy (36 correct/120 total)

The responses to this questionnaire highlighted some very common misconceptions about

the sky and the suns effect on its color. Listed below are some clarifications and


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explanations on these responses which help to answer the two main questions that this

paper sought to answer:

In addition to what results the questionnaire brought about, the colors of the sky due

to the sun can vary from a hazy yellow (Fig. 1) to a deep, rich and vibrant purple

(Fig. 2) based on the conditions of the atmosphere.

Fig. 1 Fig. 2

Photo credit: Fig. 1 Justin Miller; Fig. 2 Stephen F. Corfidi6

The reason only two colors were described in all the responses most probably stems

from the participants having been sheltered to one or only a few regions where the

conditions in the air lead to only red/pink sunsets. This, coupled with the fact that

they also dont often take the time to observe sunsets or sunrises at the opportune

time means that they dont get the chance to see the more vivid sunrises.

There appears to be a consensus that sunrise and sunset look different based on the

participantsfirst-hand experiences but the truth of the matter was that most of

them could not tell the difference when shown isolated pictures of sunrise/sunset

with no context. Though there are slight differences in the two events, the question

is difficult to answer when shown images because much of the color experienced has

to do with the perception of our eyes and how they change throughout the day.

As far as how the sun affects the color around us, the same fundamental principle of how it

creates color in sunrises and sunsets is what creates color for us at all; its white light


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which shifts creates different colors based on how the light travels. The nuances of just

how this works can be explained through the physics of light.

Color in the Sky

To understand the different colors of sunrise and sunset, we must first understand

why there is color at all in the sky. Firstly, what is color? Color is our minds perception of

reflected light whose wavelength lies in the Visible Light Spectrum. It is our interpretation

of the different facets of what we call white light an amalgamation of all the colors in

essence. Where does the white light come from? Simple the sun. The sun emits white

light constantly, providing energy and light for the whole world. So then why is the sun

yellow? This is another major misconception; the sun isnt actually yellow its white. If you

were to look at it from outer space, you would see a giant white orb.

A white sun in airless, black outer space seen from the International Space Station. Credit: NASA


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Common knowledge only tells us that the sun is yellow because 1) thats how we see it on

Earth and 2) most pictures of the sun have been colorized to fit the socially accepted color.

Using a prism, you can see how sunlight can be broken up into the spectrum of its colors:

red, orange, yellow, green, blue, indigo and violet. When you mix all those colors together,

you get white. Heres the strange part: if look at all the photons coming in, our star is

actually sending the most photons in the green portion of the spectrum. Our Sun appears

yellow to us because of the atmosphere.1The dust, gas, and water molecules in the air

scatter the light rays from the sun and since photons in the higher end of the spectrum

blue, indigo and violet are more likely to be scattered away, while the lower end of the

spectrum red, orange and yellow are less easily scattered, 1we see a yellow sun. Its

especially when the sun gets close to the horizon because its light is getting more and more

distorted by the atmosphere, scattering away more and more of the blue light and leaving

us with greater yellow light. Likewise, when the sun is high in the sky with the least

atmospheric interference, it has a bluer tint to it. This effect is the main reason behind the

different possible colors in the sky. Any adjustment in the way the light hits our vision by

means of scatter, reflection, or refraction can alter the colors and produce magnificent

effects. For example:

Historically this phenomenon has been a large part of weather lore, aiding sailors and

farmers in navigating ships and plant crops. There is an old saying that goesRedsky at

night, sailors delight - red sky in morning, sailors warning.


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Red sky at night, sailors delight:When we see a red sky at night, it means that the setting

sun is sending its light through a high concentration of dust particles, which is indicative of

high pressure and stable air coming in from the west; generally, this means that good

weather will follow.3

Red sky in morning, sailors warning:A red sunrise can mean that a high pressure system

(good weather) has already passed, thus indicating that a storm system (low pressure) may

be moving to the east. A morning sky that is a deep, fiery red can indicate that there is high

water content in the atmosphere. So, rain could be on its way.3

SunriseHistoric NWS Collection, NOAA Sunset highlighting dense cirrus cloudsHistoric NWS

Collection, NOAA.

Another source of color in the sky are volcanic ashes, which can produce a range of hues

and effects based on their current location. It is only when small volcanic particles have

been lofted well into the stratosphere that colorful sunset afterglows appear. Volcanic

particles that remain suspended in the troposphere after an eruption are comparatively

large in size and number. As a result, they attenuate sunlight and otherwise subdue twilight

hues, just like man-made dust and haze. Viewed through a veil of tropospheric volcanic ash,

a sunset is dusky and dull.6
http://www.photolib.noaa.gov/historic/nws/wea00173.htmhttp://www.photolib.noaa.gov/historic/nws/wea00173.htmhttp://www.photolib.noaa.gov/historic/nws/wea00189.htmhttp://www.photolib.noaa.gov/historic/nws/wea00189.htmhttp://www.photolib.noaa.gov/historic/nws/wea00189.htmhttp://www.photolib.noaa.gov/historic/nws/wea00173.htm


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Is There a Difference?

The study finds that the majority of people clearly see a difference in sunrise and

sunset when they look at them first-hand. However, with these same people, there is a

significant difference in their ability to decipher the two when shown an isolated image of

either of the two. Why is that? While there is some difference between the sunrise and

sunset, the biggest factor in real-life vs image experiences is the human eye. During the

day our eyes become adapted to the daylight and our pupils shrink, this means they wont

allow as much light in by the time sunset arrives. Also they become tired the effect is that

we dont capture all the colors that are really there. At sunrise, our eyes are dark adapted,

so our pupils are wider and let more light in, which lead people to record that colors are

more vibrant and brilliant. The other reason that sunrise appears so different from sunset in

person is that the particles in the air shift throughout the day, producing different effects for

both events. During the day the atmosphere becomes filled with pollution and particles,

which help to scatter the light meaning that sunsets extent of the phenomenon is wider

and covers more of the horizon. By sunrise all the air has settled down and so the sunlight

travels directly to our eyes without being bounced away first.7But an image taken by a

camera may not be able to capture the true subtle color change experienced between them.

In Conclusion

There is a lot more to color in the sky than first meets the eye. Apart from the usual

red/orange/pink sunsets, there exist a myriad of hues produced by the sun ranging from a

dusky yellow to a glowing violet all due to how the light reacts with the particles in our


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atmosphere. Our perception of these events, however, are slightly skewed because of

activity that occurs during the day vs the night: our eyes become tired while pollution

gathers in the air by sunset and they become adapted to the dark while pollution settles

down by sunrise. Whatever the case, the two phenomena have been around for the entirety

of humanity for us to watch in awe. So the next time you notice the colors of the sunset,

just take a moment to think about all that goes into it.


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Sources Referenced:

1. Cain, F. (2013, October 8). What Color is the Sun? Retrieved November 28, 2014,

fromhttp://www.universetoday.com/18689/color-of-the-sun/

2. Allaby, Michael. Weather lore. In Encyclopedia of weather and climate, vol. 2. New

York, Facts on File, c2002. p. 625-636.

3. Lutgens, Frederick K., and Edward J. Tarbuck, 1998: Weather analysis and

forecasting. In The Atmosphere: An Introduction to Meteorology, seventh edition,

Prentice Hall, Upper Saddle River, New Jersey, pp. 278-302.

4. Phan, Christian. "Survey on Sunrise and Sunset." (2014): 1-2. Print.

5. Bohren, C. F., and A. B. Fraser, 1985: Colors of the sky. The Physics Teacher, 23,

267-272 (May).

6. Corfidi, Stephen F. "The Colors of Sunset and Twilight." The Colors of Twilight and

Sunset. NOAA/NWS Storm Prediction Center, 1 Sept. 2014. Web.

.

7. Stewart, Alan, writ. Sunset vs Sunrise: Can you tell the difference?. 2014. Film. 30

Nov 2014.
http://www.universetoday.com/18689/color-of-the-sun/http://www.universetoday.com/18689/color-of-the-sun/http://www.universetoday.com/18689/color-of-the-sun/http://www.universetoday.com/18689/color-of-the-sun/

The Color of the Sky - UGS Project

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