Why Aren't The Sunrise And Sunset Equal On The Equinox?

Tools

By By Steve Pool

SEATTLE - The first days of spring and fall are a time when there is equal 12-hour daylight across the planet. However, looking at a Seattle sunset chart shows Seattle has 12 hours and 11 minutes of daylight on Sept. 21. Why?

Sunrise and sunset are calculated when the top of the sun is on the horizon. However, equal daylight is measured from the center of the sun -- accounting for a few minutes. The other discrepancy is from when the sun is on the horizon, the Earth's atmosphere bends the sun's light.

As a result, the sun still looks to be above the horizon for a few minutes after it has already set. The U.S. Naval Observatory takes this into consideration when calculating sunrise and sunset times.

For More Information -- www.usatoday.com

Your Photos

YouNews First of Spring.... Mount Baker First of Spring.... Mount Baker
This is the Grand Lady of the north ...... all laden with the winters snow. What a site to see.
YouNews  Amazing Storm Cell Amazing Storm Cell
I took a few photos of the small but strong storm cell that toppled trees at Dash Point State Park. From our view we could see the cell rotating over Sea-Tac Airport. The colors were amazing, the cloud formations were beautiful.
YouNews Seattle Rainbow Seattle Rainbow
Evening rainbow from Queen Anne using fisheye lens, 17 April 2014