The Green Flash and Inspiration

Some say it is serendipity. In reality, maybe it is just the human ability to increase awareness once your attention has been attracted. For example, you’re thinking about buying a black Subaru when you suddenly notice how many black Subarus are on the road.

Photo credit, Mila Zinkova.

I had been thinking of late about the Green Flash, a rare optical phenomenon that I experienced once, years ago, on the Pacific shore at Monterey California. It was memorable not only because of its surprising appearance, and its brevity, but because it was one of the most monochromatically pure and intense visions I’ve experienced.

I have since watched many sunsets over the water, trying to witness again what I saw in Monterrey. I recently watched for it from the air, flying towards the Gulf of Mexico as the sun set. I have watched from an elevated pavilion at St. Andrews State Park in Panama City, Florida.

So far, nothing has come even close to matching what I once saw. That is one of the givens for the Green Flash; witnessing it is oftentimes considered a once-in-a-lifetime event.

The closest I’ve come recently was seeing a greenish tint on the top part of the sun as it appeared to be half way below the horizon. My wife confirmed what I was seeing, but the brilliant flash of emerald green I saw in Monterey has eluded me.

And then like the black Subaru, I saw the Green Flash again recently in a rented 2007 movie, “Pirates of the Caribbean: At World’s End.”

But it was not the same. The Green Flash appeared in the movie like the flash from a nuclear explosion, stretching from one side of the screen to the other. There were even sound effects.

That was not the Green Flash I know.

I don’t blame Hollywood for its hyperbole. After all, I don’t think the beauty of what I once saw would convey well on the silver screen, or the TV screen. In fact photographs, such as the ones above or on the Internet fail to capture the essence of it. The brilliance of color from the flash is otherworldly — it cannot be easily reproduced.

I chuckled at the point in the Pirates of the Caribbean script when the statement is made that the Green Flash means a soul is coming back from the dead.

Master Gibbs

Ever  gazed upon the green flash, Master Gibbs?”

“I reckon I’ve seen my fair share. Happens on rare occasion; the last
glimpse of sunset, a green flash shoots up into the sky. Some go their whole lives without ever seeing it. Some claim to have seen it who ain’t. And some say—”

“It signals when a soul comes back to this world, from the dead!”

I’m as intrigued with the paranormal as the next person, but I know what 18th century pirates could not know; the green flash is a physical phenomenon, not a metaphysical one.

According to some bloggers, and Wikipedia, the purported association between souls and the Green Flash was promulgated  by Jules Verne through his fiction. Supposedly Verne claimed it to be an old Scottish legend in his 1882 novel Le Rayon-Vert, according to which, one who has seen the Green Ray is incapable of being “deceived in matters of sentiment,” so that “he who has been fortunate enough once to behold it is enabled to see closely into his own heart and to read the thoughts of others.”

Others have misquoted the passage to say that “if one were to peer in the light of the green flash they would gain the power to read the very souls of other people they met.” But that quotation is a no truer translation from the French.

As I said, Verne’s passage is a fictional myth. So, one good fiction leads to another. And of course a little Hollywood computer graphics and sound effects makes it that much better.

But what inspired me to write about the Green Flash is the resemblance, in my mind at least, between the Green Flash and inspiration.

Inspiration comes to me, and you as well I suspect, in a flash. It may be rare, but like the Green Flash it is all so clear, like a lucid dream; an “aha” moment. It is a revelation, perhaps.

Flashes of inspiration have power; they cause things to happen.  Flashes of inspiration have led me to write poetry, science fiction, and non-fiction. Some would call it the writer’s Muse: I just call it that flash of inspiration that seemingly comes from outside me.

Through a flash of lucidity, inspiration caused me to invent a new type of rebreather underwater breathing apparatus. It also caused me, at a young age, to hop on a tiny 50 cc Honda motor-scooter and ride from Atlanta to almost my destination, Kansas City. (50 cc Honda scooters are not really built for long distance cruising, but that didn’t stop me from trying and almost succeeding.)

Inspiration has caused me to raise my hands to the heavens and feel the very presence of God.

Inspiration has propelled me to pull a union thug out of a courtroom and tell him I forgave him for the assault that broke my jaw. Like the cross-country motor scooter ride, not all inspired events would be considered sane except by the person inspired. But they can be life-changing.

Unlike the Green Flash, inspiration can come anytime, anywhere. But like the emerald flash of the setting sun, inspiration can occur when you least expect it.

Both are gifts to be treasured for a lifetime.

A Look Inside Rebreather Scrubber Canisters, Part 1

If you’re diving a rebreather (closed-circuit breathing apparatus to be exact), then you know the scrubber removes carbon dioxide from your recirculated breath. Without the scrubber working, you’d go unconscious from carbon dioxide intoxication within a very few minutes of starting the dive.

But do you really know what’s going on inside that scrubber canister?

A stochastic computer simulation developed by the author gives as realistic a glimpse inside as we can get.

Loose granular and rolled sodalime. Click to enlarge.

Carbon dioxide scrubber canisters usually contain a chemical mixture called sodalime that chemically reacts with carbon dioxide in a diver’s expired breath. That material may be in granular form, or in a preformed roll. Sodalime is a mixture of calcium hydroxide and sodium hydroxide, which when it reacts by absorbing carbon dioxide is converted into calcium carbonate (CaCO3, calcite), a major constituent of limestone.

The overall chemical reaction can be simplified to:

CO2 + Ca(OH)2 → CaCO3 + H2O + heat

In the following sequence of images we see a rectangular prism shaped scrubber canister arranged axially such that the diver’s expired breath enters the section from the left, passing completely through the canister section before exiting to the right. A portion of the canister was cut away digitally after the simulation was run to allow visualization of temperatures within the canister interior.

Beginning of the simulation. Click to enlarge.

Initially, the canister is at room temperature, and then is immersed in cold water as the diver begins his dive. Temperature is color coded: the coldest temperature is black, and increasing warmth is portrayed in an intuitive fashion from purple to red to yellow, and finally white, being the highest temperature.

In the first image, CO2 has just started reacting with the sodalime at the entrance to the canister section, with a slight heating resulting. Thermal conduction is cooling the exterior surface of the canister, but most of the inside still remains at room temperature.

In the second image, the reaction front has clearly formed, and the hottest portion of the canister has begun moving downstream. Convection carries heat rapidly downstream to heat the diver’s inspired breath, and is seen to offset canister cooling due to conduction from the surrounding cold water.

Click to enlarge

In the image to the left, the heating front is fully developed, and residual heat has spread almost completely throughout the downstream portion of the canister.

In the next image, to the right, the front is beginning to weaken in intensity.




Finally (lower left figure), the thermal heating in the reaction front, indicative of CO2 absorption effectiveness, is fading out, and the cooling of the canister from the surrounding cold water is beginning to win the tug of war between heat generation and conductive cooling.

At that point in time, the canister is spent, and essentially all of the exhaled CO2 is passing right through the canister without being absorbed. If the diver had not ended his dive before his canister reached this point, he would be at great risk of passing out due to CO2 accumulation.

The last figure (lower right) shows temperature readings at various locations, and at various times (reps) throughout the simulation run. The orange and brown traces marked “temp” are measured temperatures from locations near the entrance to the canister. They rise abruptly as the absorption reactions start, and fall quickly as the reaction front moves past them, downstream.

Click to enlarge

The curves that remain elevated longer represent the average exhaled gas temperature, and the average temperature within the absorbent bed. After reaching a peak, the average bed temperature steadily drops as cold gas from the inlet (exhaled) gas chills the portion of the bed behind the reaction front. Exhaled gas temperature, on the other hand, climbs more slowly, but remains more stable until the bed becomes depleted of absorbent activity.

The monitoring of absorbent canister temperature changes is what makes the rebreather scrubber canister monitors used in the Inspiration and Sentinel rebreathers possible. The Sentinel technology is licensed from the U.S. Navy Experimental Diving Unit.

In the next posting, we’ll see the surprising way that cold canisters fill up with calcium carbonate.










The following is a high definition video of the computer simulation of heat generation and loss in a short cylindrical canister. For best effect go to full screen and 1080p mode.



Further details about the computer simulation involved in the production of these images and video can be found in the paper “Computer Modeling of the Kinetics of CO2 Absorption in Rebreather Scrubber Canisters”, in MTS/IEEE OCEANS 2001 Conference Proceedings, published by the Marine Technology Society; Institute of Electrical and Electronics Engineers; Oceanic Engineering Society (U.S.); IEEE Xplore (Online service).