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 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.