Why sky is blue?

The  sky is simple air- a covering of air  
around the earth.The sky gets its colour

because of Sunlight. Air  and the space outside
the earth's atmosphere don't have any

colour.But  sunlight contains all the colours of
rainbow in it.

When the sunlight passes

through the air, these colours are scattered. Blue
colour is scattered most. On a clear

day, the molecules of gas in the air also make
the blue colour scatter. it is reflected into

our eyes from all parts of the sky and so the Sky
looks blue to us.

         But at sunrise or sunset, the sunlight comes
to us through the  hot ,dusty, Smoky air close to
the ground. Smoke and dust make other colours,
 especially red and yellow, scatter more.Then
the sky looks red or yellow and sun seems  a
big orange ball.