ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Why is the Sky Blue? With Answer

Updated on August 23, 2013

A question that seem to be asked often by children is "Why is the sky blue?"

We adults don't ask these questions because we have gotten too used to this fact and so we no longer question it. Plus we have too many other weighty questions on our minds such as finance, jobs, politics, global warming, or whatever.

Nevertheless, this simple question is an important one and is one worthy of an answer. How do you answer it? Do you just tell the child that it simply is? Or do you give a more scientific answer?

Unfortunately, the answer to this simple question is not so simple afterall. Depending on the age of the child, he/she may not understand the explanation.

The Sky is Blue Due to Rayleigh scattering

In short, the sky is blue because of "Rayleigh scattering". But then that can give rise to more questions such as "Huh? What is that?"

So, a better answer might be the sky is blue due to the scattering of sunlight by gas molecules in the atmosphere.

Okay, but why the color blue? Each color of light has a particular wavelength. Blue light happens to the be wavelength that gets scattered the most that our eyes can see.

Rayleigh scattering is named after Lord Rayleigh (also known as John William Strutt, 3rd Baron Rayleigh), a British physicist who won the Nobel Prize for Physics in 1904 for the co-discovery of the element Argon.

Rayleigh scattering is the scattering of an electromagnetic wave by particles smaller than the wavelength of this wave. Sunlight is such an electromagnetic wave. Gas molecules in the sky are such particles. Sunlight is scattered by the gas molecules in the sky.

The sky is composed of particles mainly gas molecules, dirt, and water vapors. Sunlight is a combination of light of all wavelengths. It consists of the violet and blue light which has shortest wavelength, and it consists of the red light which has the longest wavelength, and it consists of all the other colors in between.

As sunlight passes through the sky, these tiny particles scatters the sunlight. The blue wavelengths of light is more profoundly affected than the other colors. Hence blue light scatters more and we see more blue in the sky.

When the sunlight hit the gas molecule, the shortest wavelengths (violet and blue) is scattered more strongly than the other colors. Violet light is actually shorter in wavelength than blue and hence is scattered more than blue. However, our eyes are not as sensitive to the violet range of light, so that is why we see mainly blue.

If we were to view from outer space (without an atmosphere), the sun would look white and the sky would look black.

Why is the Sunset Red?

A similar question is why is the sunset red? The answer is also Rayleigh scattering. It not only causes the blue hue of daytime sky, but it also causes the red hue of a setting sun.

At sunset, as the earth rotates, the sun is at a different position in the sky. The path that the light has to take to reach our eyes through the atmosphere is much longer than during the daytime. The shorter wavelengths (the violets/blues) has been entirely scattered, leaving us with the longer wavelength light (the reds).

Wikipedia says ...

"The Rayleigh scattering effect is therefore increased, radiating even more of the sun's shorter wavelength (violet and blue) light in different directions. The remaining unscattered light that is received by an observer is mostly of a longer wavelength and therefore appears to be red."


    0 of 8192 characters used
    Post Comment

    No comments yet.


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)