Is Sky Really Blue

"Is Sky Really Blue?"," We perceive its color because some light reflected from it reaches our eyes.
 All matter in the universe represents conglomeration of different types of molecules in diverse configurations.
 There are four basic processes that light goes through when it falls on an object.
 Of these only scattering is of any consequence when tiny particles like molecules are involved.
 This happens because the earth has a gaseous atmosphere in which oxygen and nitrogen are the dominant components.
 By light we normally mean the visible part of electromagnetic radiation.
 The color depends on the frequency or the wavelength of the radiation.
 For particles comparable to the wavelength of light the scattering depends on the wavelength.


The human eye senses color mainly through three primary colors - red, green, and blue.
 The blue component of the scattered light is almost ten times stronger than the red.
 Therefore when we look at the sky away from the sun the sky appears blue.
 If there are extraneous particles in the atmosphere as in conditions of haze, they scatter light differently and the sky does not appear blue.
 In space there is no atmosphere and no scattering particles.


In the literature we often come across the question: why is the sky blue? The use of the verb 'is' here is erroneous.
 As stated before, color is an intrinsic property of material objects and sky is not one.
 The reference to Indo-European languages is also vague.
 It consists of two parts 'aa' and 'kaashah'.
 The word 'kaashah' means visible.
 Taking the Sanskrit meaning sky means the empty space all around as far as one can see.


We see everything in the universe against the background of the sky, which is total emptiness.
 What we see are the molecules of the atmospheric gases although not directly and in the normal sense of seeing objects.
 In fact, for any human perception it is necessary to have the background of a corresponding emptiness.
 To hear a sound we need the background of silence and so on.
 From the earth it appears as a hemispherical dome because the earth is spherical.
 But what lies beyond? Nothing.
 The emptiness represented by the sky then merges with the all-pervading emptiness described by ancient philosophies and experienced in deep meditation.
 In Vedanta and Buddhism the word shunyata is used for this emptiness.


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