Blue Sky

Blue Sky

Old Elvis describes Blue in a sad but familiar melody, as we often think of “feeling blue” when we’re down in life.  But Blue really adds some joy to Life.  From the sky to the sea, to the birds and the berries, and the brilliance of a sapphire – Blue is a wonderful color, especially following a long dreary, maybe too white, winter.

“But papa, just why is that sky so blue?”  Well, near the turn of the 20th century an English physicist by the name of John William Strutt, better known as Lord Rayleigh, put the phenomena to some mathematical formulae that today we call Rayleigh scattering.

White light coming from the Sun contains all colors of light from red to blue. The molecules in Earth’s atmosphere do not scatter much of the red light, but they do scatter a significant amount of blue light.  The blue light might be scattered once or multiple times by different particles. A photon of blue light might bounce off one particle and be scattered in a random direction. It might then be scattered a second or even third time before coming down to Earth’s surface.

Blue Sunset

When we look up to the sky, we see blue light that appears to come from all parts of the sky. This light is the blue light from the sun that has been scattered from oxygen and nitrogen molecules in the atmosphere. The process is random, so blue light appears to originate from the entire sky. Knowing why the sky is blue can increase your enjoyment of a nice day. Remember the sky is called ‘Carolina blue’ not because God is a tarheel but because of Rayleigh Scattering.

(click on any picture for more information)

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Natural Blue:

Indigo dye is an organic compound with a distinctive blue color (see indigo). Historically, indigo was extracted from plants, and this process was important economically because blue dyes were once rare.  Nearly all indigo produced today — several thousand tons each year — is synthetic.  It is the blue of blue jeans.

Indigo Chemical Structure

2,2′-Bis(2,3-dihydro-3- oxoindolyliden), Indigotin

Indigo Plant

Indigofera Tinctoria

Blue Dye

Blue Jeans



Gotta love those Blue movie characters too!.

There’s Megamind, Smurfs, Blue of Blues Clues, Sully of Monsters Inc., Eeyore of Winnie the Pooh and the Genie from Aladdin, just to name a few.








This was too cool not to include…

The Amazing Pendulum Wave Effect

Click on picture for video

For Sound version please visit our TIME page.

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Link to Blue Music


Links to other Life Colors pages:



Thanks for visiting Blue!

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