Spend enough time on Maui, and there’s a very good chance you’ll hear tell of the “Green Flash.” And that’s for very good reason: The Valley Isle (and, for that matter, the rest of the Hawaiian archipelago) is one of the best places in the world to see this optical phenomenon.
In this article, we’ll talk about what the Green Flash is, its basic cause, and where/how to see it during your Maui vacation!
Introducing the Green Flash
The Green Flash is a very brief flare of emerald hue seen at the very tail-end of sunset, or right at the cusp of sunrise. The flash appears as a smudge, dot, or even vertical streak right above the upper rim of the sun. It lasts mere seconds, so “flash” is indeed an accurate description.
Also known by various other names—including more poetic ones, such as “Neptune’s Wink”—the Green Flash is uncommon to see. As we’ll get into, though, the conditions most conducive to its appearance are commonplace in Hawaii. Your odds of seeing this coveted blip of green above the sun are quite decent in Maui. That’s especially true if you’ve got enough time to stack up a week or two’s worth of sunsets!
As we’ve already said, you can also see the Green Flash just before the sun’s disc appears at daybreak. But this is a tougher proposition, mainly because it’s hard to know exactly where to look on the horizon in that pre-sunrise moment. You want to be looking just above the very top of the sun right before or when it hits the skyline. Until that topmost solar rim appears, you’ll only have a rough idea of that location. Because of the brevity of the Green Flash, you might well miss it while looking off in a slightly different direction.
Plus, you’ve got to have the gumption to get up early! Sunsets are both more convenient to monitor and offer the easier setup for zeroing in a likely Green-Flash location.
The Science Behind the Green Flash
The simplest, shortest explanation for the Green Flash has to do with atmospheric refraction. Refraction refers to the bending of light from a source, in this case the sun.
When the sun is low in the sky, its light separates out into component colors based on their different wavelengths, in the manner of a prism. Longer wavelengths are refracted (or bent) less than shorter ones. Thus, longer-wavelength colors such as red vanish first, while the disappearance of shorter-wavelength ones such as blue and violet is more delayed. Green has a medium wavelength, so you would expect it to disappear sometime between red and blue/violet.
But sunlight is also affected by atmospheric scattering. Atmospheric molecules such as water vapor as well as tiny airborne debris scatter sunlight. Shorter wavelengths are more scattered. This is why, when the sun’s high in the sky, the sky looks blue: This short wavelength is highly scattered and so that color dominates from our earthbound perspective. When the sun’s low in the sky, its light has to pass through a lot more atmosphere to reach our eyes. The short-wavelength blue is scattered out and disappears, and the sunrise or sunset sky takes on the red cast of the longer, less-scattered wavelengths.
Because of scattering, the final refracted blues and violets of sunset tend not to be visible. The medium-wavelength green, bent more than red, is thus often the very last bit of sun color to be seen—hence the Green Flash. (In exceptionally clear atmospheric conditions, though, a “Blue Flash” is sometimes seen.)
The Green Flash is enhanced by the mirage effect of the refraction-created “green rim” of the low-lying solar disc dipping below the horizon. Because of this, a very flat horizon gives you the best chance of seeing the flash. You can’t do better than the ocean skyline on this count. And because too much haze will scatter out the green and thus prevent a Green Flash from occurring, you want low levels of air pollution for the best chance to spot one.
It so happens that vast, flat seascape horizons are mighty easy to come by in Hawaii. And, furthermore, this is the most remote major archipelago in the world, surrounded by huge reaches of open ocean, so the air is generally wonderfully clear. That’s why Hawaii—Maui very much included—is such a great place to look for the legendary Green Flash.
Where to See the Green Flash on Maui
Numerous beachfronts or headlands on Maui with broad ocean sightlines to the west are ideal for watching for the Green Flash at sunset. East-facing shorelines set you up for the less-easily-seen sunrise Green Flash. (If all the conditions line up perfectly, it might be possible to see the Green Flash while taking in the famous sunrise from Haleakala summit.)
A whole slew of popular west-facing Maui beaches—from Kapalua or Kaanapali in West Maui south to the Kamaole or Makena beaches of South Maui—offer fine Green Flash vantages. Your chances during any given sunset might still be fairly low, but the level ocean horizons and low air pollution provide pretty reliable Green Flash ingredients, at least.
Another option is to leave land altogether and enjoy a sunset sail, which gives you an even more unobstructed view of the sundown spectacle. Sunset helicopter tours would be another unique option for, just maybe, goggling at the Green Flash over Maui.
Remember to avoid looking directly at the sun during sunset. Most importantly, that risks eye damage. Furthermore, you’re liable to have a blazing retinal image of the sun that may prevent you from being able to see the brief pulse of the Green Flash.
The great thing is that Maui sunsets are gorgeous whether or not the Green Flash makes a cameo. So make an effort to enjoy each and every one of them during your trip, and maybe you’ll land a glimpse of this famous, split-second beacon of green!