sky

Hello rinav001,

The short answer to your question is that sunlight is scattered by molecules in the atmosphere, in a process known as "Rayleigh Scattering". Shorter (i.e. bluer) wavelengths are scattered more, which means that when you look at the sky in directions away from the Sun, you see this blue scattered light.

There's a lot more information about this on various webpages which you can find by a google search for something like "why is the sky blue?".

For example:

http://math.ucr.edu/home/baez/physics/General/BlueSky/blue_sky.html

or

http://www.badastronomy.com/bad/misc/blue_sky.html

and an in-depth explanation is available at:

http://world.std.com/~mmcirvin/bluesky/index.html