Capturing a green flash

07-11-2013

 

 

Article by David Bear:

I've always been attracted to the illusory, especially those rarely occurring or seldom witnessed phenomena that demonstrate the subtle beauty or infinite power of nature.

Something about the incomparable and often awesome displays arranged by Mother Nature puts mankind's puny performances in perspective. The feeling of being a rare observer to one of those events also contributes to a sense of personal accomplishment.

Seeing a green flash falls into that category. I recently bagged my first green flash, after decades of looking.

For those who may not be familiar with the term, a green flash is an atmospheric optical phenomenon. When conditions are right, at either the first moment of sunrise or the last of sunset, a brilliant, tight band of turquoise can flash along the horizon, generally lasting less than a second.

Although the specifics are complex, the generally accepted explanation is simple. It attributes green flashes to rays of the rising or setting sun passing obliquely through a thicker slab of atmosphere than when it is higher on the horizon. That longer passage through the air tends to split the light into the spectrum of colors. Since the atmosphere absorbs the reds and oranges and scatters the blues, what gets through most often is a green that usually is too faint to be seen by human eyes.

But sometimes if the weather is clear, the atmosphere can focus the greens along the horizon on either side of the setting sun. A careful observer in the right position, ideally at a high vantage point, may see a tight ribbon of intense color flash along the horizon at the moment the sun dips below the plane of the planet.

Bingo.

Since the flash lasts only a second and there are no instant replays, to see one, would-be observers must not only be in the right place at the right time but also be paying close attention to the horizon. For centuries, green flashes were considered to be somewhat mythical, since they are so difficult to observe, even if you know what you're looking for. But in recent decades, color photography has captured numerous examples of green flashes. For example, in 1986, scientists at Cape Kennedy photographed a green flash against the plume of a night missile launch. This photographic proof makes the green flash phenomenon slightly less elusive than the Loch Ness Monster.

Although theoretically green flashes can be seen almost anywhere there's a clear, unobstructed view of the distant horizon, say from a mountaintop, airplane or even a tall building, the places they're most commonly viewed are on east- or west-facing ocean shorelines. That may also have something to do with the fact that those are also places where lots of people regularly spend time looking at sunsets.

Obviously, seeing a green flash depends on an observer being there as the phenomenon actually occurs. Something like the noise a tree falling in the forest makes when no one is around to hear it, green flashes are firing off all the time somewhere or another around the planet, unseen or appreciated by human eyes.

The primary tactic for seeing one is to put yourself in a likely spot and wait patiently and attentively, hoping that one occurs while you're looking. Unfortunately, accomplishing that can be more difficult than it might seem.

For years, when I've found myself at a shore at sunset (far more common for me than sunrises), I've scanned the horizon unsuccessfully for a glimpse of a green flash. While I have the intellectual confidence to know that green flashes are real, you never really "know" until you see one for yourself.

My personal search was satisfied several weeks ago, as my wife and I were standing in the warm South Atlantic maybe 50 yards off the beach at Parrot Cay. It was the final afternoon of our week visit to the Turks and Caicos, and we were both very relaxed. A band of showers had passed through several hours earlier, leaving the atmosphere crystal-clear. Streaks of high, puffy clouds were draped across the sky over our heads, but the long ocean horizon to the west was cloudless, which is important, because anything that obscures the view will prevent a flash from forming.

Just being in that place and time was blissful and conducive to mindless reveries, but I managed to keep focused on my mission, observing the setting sun.

Now, it's never safe to stare directly into the orb of the sun, even when it's low on the horizon. So you have to soften your gaze but focus your attention. Wait a minute, then five, then 10, avoiding getting too distracted up by the stupendous, evolving palette of the sunset, the mandarin oranges, electric azures and peacock purples.

My reward came just at the moment I was about to give up for the day.

As old Sol's final morsel slipped below the waves, two capillary pulses of pure aqua green coursed along the rim of the horizon for an instant before culminating in tiny fillips of light at either end. They were gone almost before I even aware of them being there.

"Did you see that?" I asked my wife, excitedly.

She shook her head. Even though she'd been looking at the same sunset, her attention must have wandered. Or maybe, because I am a head taller than she is, my perspective was that much different.

Or maybe I hadn't seen anything at all. After I had looked longingly for so many years, perhaps my powers of suggestion had taken over and created a personal mirage. After all, my only evidence was in my memory, and how can you share that with someone else?

Naturally, Sari was somewhat skeptical, but even now, weeks later, the image in my mind's album remains strong and splendidly beautiful. I doubt it will ever fade.

So I can now tell you with absolute confidence that green flashes are not figments of imagination. Or anything else. Keep looking and perhaps you'll see one too.

For more explanation of green flashes, along with links to a portfolio of photographs, visit http://mintaka.sdsu.edu/GF

[Back to Articles Main]