Why is the rising sun red?

Answer 1

The sun radiates as a black body, meaning that it radiates light at all wavelengths including blue, red, orange, yellow, green, UV, Infrared, etc. Obviously humans can only see the visible light from the sun. When the sun is on the horizon, the light coming to us from the sun, due to the angle it hits the atmosphere, must go through a much thicker atmosphere than if it were right above. At an angle of about 10 degrees, or the height of a rising sun, it must pass through the equivalent of 11 atmospheres. Due to properties of the atmosphere blue light is reflected much more than red light, and red light can penetrate farther into the atmosphere before being reflected away. Thus the light from the sun at the horizon looks red because the red light can reach us but the other light such as blue gets reflected away before it reaches us.