This week’s photo contest on I Didn’t Blink is sunsets. I immediately thought of this picture I took about a week ago.
Why are winter sunsets redder than summer sunsets?
First, remember why sunsets are red to begin with: when the sun is at a low angle in the sky, sunlight has to pass through more air to reach your eye. The atmosphere is better at scattering blue light than red light, so most of the blue light is scattered away.
During the winter, the angle of the sun is lower than it is in the summer, so it makes sunsets, which are already red, even redder.
[Side note for math nerds: if you’re comfortable with spherical coordinates, imagine a spherical coordinate system centered on the Earth, oriented along the Earth’s axis. We can describe the position of the sun in the sky in terms of phi and theta. Phi, the azimuthal angle, depends on the time of day. Theta, the polar angle, depends on the time of year and the latitude. The amount of atmosphere sunlight has to travel through depends on both angles.]