Why does the Sun look like a red disc during sunrise and sunset?

During sunrise and
sunset, the sunlight
has to travel a much
longer distance than
during the rest of the
day. The scattered blue
light is not able to cover
this extra distance and
therefore does not
reach our eyes. The
red light reaches us, as
the wavelength of red
is longer. This helps
red light travel further.
This is why the Sun
appears like a red disc.