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Taking scuba to new depths

If I end up completing all the tasks on my Life’s To Do List, I’ll live to be a very old man indeed. So many places to visit, books to read, foods to try, experiences to have—and the list is perpetually growing. “Learn scuba diving” is on the list, but like “visit Machu Picchu” or “have sushi at Sukiyabashi Jiro,” it’s something that requires a greater investment of time and money than I am able to make at the moment. Still, it’s something I’d like to do if the opportunity ever presents itself. Yes, there’s a lot of fascinating stuff underwater—the marine life, the shipwrecks, and all—but equally appealing is the geek factor. Scuba diving requires lots of cool, specialized equipment, and just think of the entirely new range of dive-enhancing gadgets I could justify buying!

Then perhaps one day, if I become sufficiently advanced and still have some money to spare, I’ll invest in the ultimate piece of scuba gear: a rebreather. This fabulous piece of kit could set me back as much as US$20,000, not to mention the extensive additional training and certification I’d need to use it. But a rebreather does for scuba diving something like what a hybrid engine does for a car: it provides much greater fuel efficiency while reducing noise and pollution. These things may not seem like a big deal on the road, but underwater, they can make all the difference in the world. (Rebreathers are also used in spacesuits and gear for mountaineering and firefighting, among other applications, but I’ll focus on the underwater use here.)

Heavy Breathing

In ordinary scuba diving, you have one or more tanks of air—or, depending on what sort of dive you’re undertaking, a mixture of oxygen with nitrogen, helium, or other gases in carefully measured proportions. Regulators deliver just the quantity of air you need, at an appropriate pressure, through a mouthpiece; when you exhale, a valve releases the used air into the water. Each time you take a breath, though, your lungs absorb only about a quarter of the oxygen in the air; the rest is exhaled along with the carbon dioxide you produce. So a lot of the oxygen divers take with them is essentially wasted. The deeper you dive, the more rapidly you use up air, so a dive’s maximum duration is determined by its depth and the number of tanks a diver carries. Even though air tanks don’t feel heavy underwater, there are practical limits to how much a diver can carry, and thus limits on the duration of a dive.

Rebreathers change this equation by recirculating the unused oxygen from every exhaled breath. Instead of being expelled into the water, the used air is channeled into a “scrubber,” an assembly that uses a chemical such as a soda-lime mixture (sodium hydroxide and calcium hydroxide) to absorb the carbon dioxide. That leaves a good bit of usable oxygen, which is recirculated into the system and supplemented, as needed, with more oxygen from a tank. In this way, a rebreather can provide dramatically longer dive times with a much smaller and less cumbersome apparatus. In addition, because air isn’t discharged into the water when you exhale, there are no bubbles (or at least very few). As a result, a diver wearing a rebreather can swim almost silently and invisibly—handy if you’re photographing bashful fish or, you know, sneaking up on the enemy spy who’s trying to sabotage your submarine.

In the Loop

Conventional scuba apparatus is “open-loop” (or “open-circuit”), meaning the air goes out of the system when it’s been used. Most rebreathers, by contrast, fall into one of three major categories:

• Oxygen rebreathers are the simplest variety. They use a single tank of pure oxygen, but because of the danger of oxygen toxicity (a situation where pressure forces too much oxygen into the blood), they can be used only at shallow depths of about 6 meters (20 feet) or less.
• Semi-closed circuit rebreathers replace the oxygen tank with a tank of mixed gases, allowing deeper dives. But their design also requires that a portion of the used air be vented into the water to maintain the proper levels of oxygen and other gases.
• Closed-circuit rebreathers are the most complex design. They use two gas tanks: one for air (or at least an oxygen-nitrogen or oxygen-helium mixture) and one for pure oxygen. Oxygen sensors feed data to a microprocessor that regulates the oxygen pressure in such a way that no gas needs to be expelled. Closed-circuit rebreathers also enable the diver to maintain very low levels of nitrogen (or other non-oxygen gases) in the blood, which reduces the need for slow decompression when ascending from deep water.

As great as rebreathers are for certain applications, they have some disadvantages compared to conventional scuba gear. For one thing, because rebreathers are so complex, more things can (and do) go wrong. They must be carefully maintained—and even then, they are far more prone to failure than a simple tank-and-regulator setup. (Failure of one’s breathing apparatus deep underwater, of course, is a rather serious problem.) In addition, it’s surprisingly difficult to regulate oxygen pressure precisely so that it falls into the narrow range between too little (which can result in a potentially deadly condition known as hypoxia) and too much (which can result in the potentially deadly condition of oxygen toxicity). If a rebreather fails to deliver just the right mix of gases, the diver is in trouble.

And of course there’s the price, which is not a big deal for the military, but problematic for many recreational divers. Note to self: Put “become fabulously wealthy” higher on Life’s To Do List than “learn to use a rebreather.”

Note: This is an updated version of an article that originally appeared on Interesting Thing of the Day on February 17, 2005.

Image credit: Peter Southwood [CC BY-SA 3.0], via Wikimedia Commons

Years ago I ran across a job listing at Apple, and although I don’t recall the specifics, I remember one of the job requirements being the ability to “multitask while multitasking.” And I thought: Ha ha ha ha hard pass. Multitasking is a thing that computers can (sort of) do; it’s not something that humans can do. There are people who think they can multitask, but study after study has shown that when we try to switch rapidly among tasks (which is what multitasking really means, after all), our overall efficiency decreases quite a bit because of the extra cognitive load involved in getting the brain back up to speed where it left off on a previous task. In other words: it’s an illusion, and people who try to do it are not just fooling themselves; they’re actually decreasing their productivity. So just cut it out, already! Today is Single Tasking Day, and you celebrate it like this: Do one thing at a time. That’s it. Finish the thing, or get as much done as circumstances permit, then do the next thing. Repeat indefinitely.

While we’re on the topic…who decided that “single tasking” is the term for the opposite of “multitasking”? It should be “unitasking,” which is what I call it and what I (try to) do!

Image credit: John LeMasney [CC BY-SA 2.0], via Flickr

Shooting game

One day Morgen and I were having a brainstorming session about interesting things related to the theme “hit or miss.” As we began talking about things that involve hits and misses. Morgen said, “Do you know what the national sport in Bhutan is?” I was embarrassed to admit I did not even know exactly where Bhutan is located; it’s simply not a place I’ve ever spent much time thinking about. Morgen told me that Bhutan is between China and India. Although this didn’t give me any strong clues, I made what I thought was a safe guess: soccer. That turned out to be a particularly bad guess, because Bhutan’s national soccer team is nearly always among the lowest-ranked in the world. In 2002, it was ranked 202 out of 203 worldwide; FIFA sanctioned a special match that year, at the same time as the World Cup finals, between Bhutan and 203rd-ranked Montserrat; the match was covered in a documentary film called The Other Final. (Bhutan’s soccer ranking has since risen all the way to 186—go, team!)

In fact, Bhutan’s national sport is archery. That fact alone, I think, qualifies as an Interesting Thing, but there’s more to the story.

Weapons of Play

Bhutan is a Buddhist nation, and one of the central precepts of Buddhism is a reverence for all life. So it seems somewhat incongruous that the nation’s favorite game involves a hunting instrument (or, depending on how you look at it, a weapon of war). But in Bhutan, the bow and arrow can be used only for play. In fact, when making arrows, one can use only feathers that were found on the ground; killing a bird to obtain its feathers would be considered wrong.

Each village has its own archery range, making them as common as curling rinks in Canada. (That is to say, extremely common.) Although modern, high-tech equipment is making some headway, most competitors use traditional, hand-carved bamboo bows and arrows. Village teams compete against each other in rowdy, elaborate, alcohol-fueled, multi-day tournaments that are as much about spectacle as they are about hitting a target. Archers can use almost any means at their disposal to distract or demoralize their opponents, including dancing in front of the targets. A major part of the sport goes on behind the scenes, as teams conspire to throw off their opponents’ game. It is this, rather than what I typically think of as team interaction, that gives Bhutanese archery such popularity.

The Wide World of Archery

You might imagine that since archery is the national pastime, Bhutanese archers would be world-renowned for their skills. So far, however, the country has not distinguished itself in international competition beyond Asia. Until 2012, archery was the only Olympic sport in which Bhutan participated (now they also compete in the women’s 10m air-rifle event), and they have been sending their best archers to the Olympics since 1984. But the country has never received a single Olympic medal. This is largely due to the fact that traditional Bhutanese archery is much different in both equipment and style from Olympic archery—insulting your opponent during Olympic competition is, shall we say, bad form. But Bhutan remains optimistic that their athletes will eventually earn recognition as the world’s finest archers.

I’ve tried archery only a couple of times, and I found it a lot harder than I’d imagined. And in America, at least, I would consider it rather unsafe to taunt someone who’s pointing a deadly weapon in my general direction. All the same, I think I could get behind a national sport that is as much about fun and mischief as about skill.

Note: This is an updated version of an article that originally appeared on Interesting Thing of the Day on December 25, 2004.

Image credit: Göran Höglund (Kartläsarn) Hoffman [CC BY-ND 2.0], via Flickr