Why is ther sunset red?

Believe it or not, the sunset looks red for the same reason that the sky looks blue during the day! It's true!

"White" light from the Sun contains all the wavelengths of light, every color. As the light passes through the atmosphere, a lot of it goes pretty much straight, but some of it - more blue than anything - gets scattered and comes back to your eye from every direction. So the blue sky color light is sunlight that got scattered. Some of the light doesn't get scattered so much, but it does get refracted, and red more than other colors. So when you're looking at the red sunset - or the red sunRISE, same thing - you're seeing what's left of the white sunlight after the blue got scattered back over the daytime part of the Earth, and the red made it to the horizon.