San Felipe, Baja, Mexico

The sun is visually, although subtly, variable depending upon the time of day. It may be yellow during midday, but it gradually changes its color as sunset approaches. This is caused by the effects of scattered light. When sunlight comes into contact with something, even atomic particles in the atmosphere, it is either absorbed or reflected. The things we see around us gain their colors from the part of the spectrum reflected (or transmitted if the object is transparent). A red apple absorbs most of the light that hits it, except for the red part of the spectrum, which it reflects back to our eyes.

Sunset from Shadetree Computer Services
Rare sunset from deck of Shadetree Computer Services

Because the atmosphere consists, for the most part, of nitrogen and oxygen atoms, which share a talent for scattering higher frequency violet light, they reflect that part of the light spectrum. Our eyes are more sensitive to blue rather than violet light, so we see the sky as blue. The lower frequency rays, red, orange and yellow, are not scattered and reach our eyes more or less without interruption. The lower frequencies, including yellow, are received from the sun this way. And because the sun produces strong yellow light frequencies, we see it as yellow during the part of day when its light comes to us most directly.

When the sun is closest to perpendicular to the earth's surface, its light travels the shortest distance through the atmosphere. But as the sun approaches the horizon line, sunlight must travel a greater distance through the atmosphere to reach our eyes. As the distance increases in length, the full spectrum encounters more and more atmospheric particles. This results in the scattering of greater amounts of yellow light. During sunset hours, the light reaching our eyes tends to be more loaded with red and orange frequencies of light. This is why sunsets have a reddish-orange hue. The effect of a sunset becomes visually more impressive if the atmosphere contains greater amounts of particles. The presence of sulfur aerosols (an industrial pollutant) in the air contributes to some magnificent sunsets. Here in the Baja, particles from dust kicked up by wind, which can contain any number of chemical particulants, can cause some truly beautiful sunsets. But these are more rare than spectacular sunrises. This is because there is less of an opportunity for the atmosphere to inhale large amounts of particles and pollutants to the west of the Baja. The peninsula is narrow and rubs up against the vast expanse of the Pacific Ocean. But across the Sea of Cortez, to the east, is mainland Mexico, which has plenty to offer the atmosphere in its quest for the Perfect Sunrise.