Winter Sunset

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.]

Advertisements

About Rachel

I'm a grad student in the physical sciences at the University of Michigan and mother of one.
This entry was posted in Nature. Bookmark the permalink.

One Response to Winter Sunset

  1. Ashley Sisk says:

    Absolutely beautiful.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s