Archive for October, 2009

Orange Sunsets

October 5, 2009

So I was watching my favorite NFL team, the Denver Broncos, today take it to the Dallas Cowboys and I was thinking about bumper stickers I used to see in Denver – “If God wasn’t a Bronco fan, then why are sunsets orange?”  Then I thought, why are sunsets orange?  Living here in Tucson, we’re lucky to have spectacular sunsets nearly every night and one of the best places to see this is half-way up the Catalina Highway at the Windy Point pulloff – definitely worth the drive up there.

Anyway, back to our question – why are sunsets orange?  Well, after looking into this, it’s an effect that is due to the thickness of the atmosphere that sunlight passes through in the evening.  At midday, sunight passes through the thinnest portion of atmosphere and the amount of light scattering is the least – sunlight is it’s brightest and it looks “white”.  Now when the sun is setting, sunlight is hitting the atmosphere at an angle, passing through more atmosphere, and is scattered.  Blue and green light is scattered while yellow, orange and red light is least scattered making the beautiful sunsets we see.