Why is the sky blue?

There have been many theories about light and its
components. Isaac Newton in his Particle Theory of Light, discusses the fact that white
light is, in fact, composed of a series of colors. The colors separate and can be seen
through a prism as individual colors. Prisms, such as those used by Newton to support
his theories, make light bend. Mirrors reflect light and the atmosphere or the gases
present in it, make light scatter. It is this scattering of light which is responsible
for the blue sky color. 

Newton and his peers argued over
light and light particles or light waves and Newton's contribution cannot be overlooked.
It was however, Einstein, approximately two hundred years later, in 1911, who finally
resolved the issue of light and its distribution (The Quantum Theory of Light).
Einstein, from a complicated formula, calculated how light scatters from molecules.
Light, a form of energy, travels in electro-magnetic waves and blue has a shorter
wavelength and less mass than most other colors, except violet but this is, mostly
absorbed at higher altitudes and the eyes are less sensitive to
violet.

However, Lord John Rayleigh, an English physicist
first described the phenomena of light scattering in 1870, as proposed by John Tyndall
some years earlier, and it is the so-named Rayleigh scattering which is responsible for
the blue color of the sky. Short wavelengths, such as blues, are absorbed by gas
molecules (oxygen and nitrogen) in the atmosphere and then radiated out in different
directions which ensures that blue reaches all directions.