Have You Seen Puerto Vallarta's Green Flashes?

Perhaps you're among those fortunate enough to have witnessed a green flash at the instant the sun sets; however for most, they've only heard of the phenomenon. One such area for viewing the green flashes is Puerto Vallarta, Mexico where, during the "high season" of November through May when the average daily temperature is 73°F with virtually no chance of rain, thousands of people religiously watch for this rare instantaneous event every evening at sunset.

According to most physicists, green flashes involve physical optics as well as physiological optics. The factors contributing to the high frequency of green flash sightings in Vallarta can be categorized as follows:

1) Physical optics- By means of refraction and dispersion of the sun's rays, the various length light waves reach the eye at slightly different times and speeds. Light moves slower in the cooler denser air, hence the higher frequency light waves, i.e., those with the shortest wave length (green & blue), are Sunset boat puerto vallarta refracted more than are the lower frequency light waves (red & orange). This greater degree of refraction or bending allows the green and blue light waves to be seen over the earth's curvature immediately after sunset, whereas the red and orange light waves are blocked by the earth. Atmospheric inversions and temperature gradients may even increase the separation of light waves creating a more vivid green flash. Any degree of haze in the air will disperse the very shortest of the light waves which are the violet and blue colors of the spectrum, thus leaving green to be the last color seen.

During the winter months in Vallarta, it's not uncommon to have an evening air temperature the same as the Banderas Bay water temperature. The air is always very clean and clear and there is often a small amount of haze; making conditions ideal for observing green flashes at sunset.

2) Physiological Optics-After looking at the bright sun, even for a few seconds prior to sunset, there is some degree of bleaching of the retina's red-sensitive cone photo pigment. This bleaching effect, sometimes referred to as red fatigue, distorts color perception; thus causing the light seen just before final sunset that would normally be perceived as yellow, to appear as green.

As an important reminder, the brightness of the sun changes by a factor of two every minute prior to sunset. Therefore, it is safe to look at the sun when its right down on the horizon but staring at it just a minute or two prior to sunset could result in eye injury. As a rule of thumb; if the sun is too bright to look at comfortably, don't look at it!

3) Psychological or other influences-After attending hundreds of parties in Vallarta over the past ten years we have noticed that the odds of seeing green flashes (not to be confused with hot flashes) are directly proportional to the quantity of margaritas consumed! This is especially true with women because they seem to observe the green flashes much more often than do men. Since there is no empirical data or scientific explanation for this phenomenon, we can only attribute this to the party atmosphere that exists nightly in Vallarta.