Question

why does the sky sometimes apear white

Answer 1

because of the scattering of blue light in all directions which causes it to look whitenear the horizon.

Answer 2

Blue light is scattered in all directions by the tiny molecules of air in Earth's atmosphere. Blue is scattered more than other colors because it travels as shorter, smaller waves. This is why we see a blue sky most of the time. Closer to the horizon, thesky fades to a lighter blue orwhite.