Posts by Big Pete

Freediving in Ireland

Taking the oxygen-free plunge

Lifeguards at public swimming pools don’t like it when you disregard the signs that say “Walk, Don’t Run!” But they like it even less when you don’t move at all. As a lifeguard is scanning the pool, the last thing they want to see is a body floating face-down and motionless in the water. I remember getting yelled at for doing exactly that when I was about 10 or 12 years old. I couldn’t understand what the problem was. I wasn’t bothering anyone, I was just enjoying the sensation of holding my breath, floating, and staring at the bottom of the pool. But the lifeguard reprimanded me: “You have to keep moving! Otherwise I won’t know if you have drowned.” I thought that was unfair, because kicking around in the water isn’t as relaxing or serene as just floating there, but ever since then, as a courtesy to those who could not discern my state of consciousness from a distance, I have refrained from floating face-down.

Little did I realize that what I was doing would soon be a major competitive sport.

Kicking the Breathing Habit

Serious breath-holders would call what I was doing Static Apnea—just one of several categories of the sport of freediving. The current world record for Static Apnea is held by Serbian diver Branko Petrović, who floated in a swimming pool while holding his breath for eleven minutes and fifty-four seconds. That is, if I may say so (and pardon the pun), an unfathomably long time. But it’s just the tip of the iceberg. Freediving is all about pushing the limits of physical and mental endurance, defying common sense all the way.

Freediving is the name for a class of activities that involve holding one’s breath underwater for an extended period of time. In its simplest form, freediving is a low-tech alternative to recreational scuba diving. Although freedivers can’t stay submerged as long as divers who use tanks and regulators, they can move much more quickly and freely without the drag caused by the equipment. It’s a quieter experience too, and with fewer bubbles there’s less chance of scaring off fish. The only equipment required is a mask, wetsuit, and extra-long fins, making it a less expensive pastime than scuba diving as well.

The Length and the Breath

But when you start talking about competitive freediving, it begins to sound like a sport that could only be appreciated by someone whose brain had been deprived of oxygen a bit too long. Static Apnea is all well and good, but serious freedivers consider that just the first step. Dynamic Apnea ups the ante by requiring the diver to swim horizontally underwater; the idea is to cover as much distance as possible without taking a breath. Separate categories exist for divers using fins and those without. But then things start getting really interesting. In the other major forms of freediving, a rope (with markings to indicate depth) is dropped to the sea floor, and the objective is to follow the rope as deep as possible before returning to the surface. In a Constant Ballast dive, divers must descend and ascend under their own power; they can optionally use a weight to help them descend but they must carry the same weight on the way back up. Free Immersion is similar, except that the diver can pull on the rope to assist in the descent and ascent. Then there’s the Variable Ballast dive, in which a weighted sled takes the diver farther down into the water; the diver then leaves the sled to ascend under his or her own power. If that’s not challenging enough, a No Limits dive uses the same weighted sled to go even deeper, at which point the diver inflates a lift bag to facilitate a speedy ascent.

Austrian diver Herbert Nitsch currently holds the world record for No Limits free diving, generally considered the most challenging category. On June 14, 2007, he made a record No Limits dive of 214m (702 feet). But freediving is intensely competitive, and records are set and broken with astonishing frequency. The endless push to go deeper and longer is, not surprisingly, very risky, even for extremely well-trained divers. In October 2002, world-renowned freediver Audry Mestre died in an attempt to break the record at the time with a dive of 170 meters. A combination of equipment malfunction and human error prevented her from ascending fast enough, despite the numerous safety measures that are always taken during dives of this sort. Similarly, in November 2013, Nicholas Mevoli from New York died in an attempt to break the Constant Ballast Without Fins record. But these tragedies seem to have had a galvanizing effect on the freediving community, inspiring them to push themselves even further as a tribute to their lost comrades.

If you think about other mammals that hold their breath to make extended dives—whales, seals, and sea lions—freediving doesn’t sound all that crazy. Human physiology is quite a bit different, but research has shown that with training, almost anyone can develop the ability to hold their breath for three or four minutes. Still, there’s a big difference between holding your breath on the surface of a nice, safe swimming pool and doing the same thing under hundreds of meters of water. That requires stamina, guts, and probably a little insanity.

Note: This is an updated version of an article that originally appeared on Interesting Thing of the Day on July 30, 2003, and again in a slightly revised form on March 22, 2005.

Image credit: Simukas771 [CC BY-SA 4.0], via Wikimedia Commons


Source: Interesting Thing of the Day

Diver using a rebreather

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


Source: Interesting Thing of the Day

Digs and Buildings, Oak Island, Nova Scotia, Canada, August 1931

Nova Scotia’s notorious money pit

Canada’s maritime provinces may not be the first place you think of when you hear the words “buried treasure,” but for over 200 years, treasure hunters have had their eyes on tiny Oak Island in Mahone Bay, Nova Scotia. Over the years, millions of dollars have been spent—and at least six lives lost—in repeated attempts to excavate one of the world’s most infamous alleged treasure sites. What could be worth so much effort? Possibly an enormous cache of gold and silver, ancient manuscripts, or…nothing at all.

Can You Dig It?

The story begins in 1795, when a boy was wandering around on the island and found a curious depression in the ground. Right above this depression was an old tackle block hanging from the limb of a large oak tree, as though someone had used it to lower something heavy into a hole. Having heard stories about pirates frequenting the area in centuries past, the boy immediately suspected buried treasure. He returned the following day with two friends and began digging. A few feet down, the boys found a layer of flagstones; 10 feet below that was a wooden platform. Both of these markers strongly suggested the hole was man-made. They kept going, but by the time they reached 30 feet, they realized there was no end in sight and called it quits.

Several years later, having secured some financing and additional help, they returned, this time digging to more than 90 feet—hitting several additional wooden platforms on the way down. At 90 feet they found a stone inscribed with strange symbols they could not decipher. (Later, some would claim that the symbols were a cipher for “Forty feet below two million pounds are buried,” but that stone was soon, conveniently, lost.) Just below that was a layer of mud. Probing down into the mud with a crowbar, they hit another solid surface—perhaps another wooden platform, or perhaps a treasure vault. But when they returned the next day, the shaft had filled with 60 feet of water, which foiled all attempts at bailing. Shortly thereafter, they tried to dig a parallel shaft, thinking they’d get below the treasure and tunnel in horizontally—but this second shaft filled with water as well. The first crew of treasure hunters abandoned their dig.

In 1849, a second group attempted an excavation. Then another, and another, and another. Each time, treasure hunters made some intriguing discovery, but each time, their attempts to go deeper were frustrated—by flooding, cave-ins, accidental deaths, and other misfortunes. On several occasions, workers attempted to drill into the earth beneath the water that filled the pit, and the drills brought up some interesting fragments—a piece of gold chain here, some wood there…and a small scrap of parchment that had one or two letters written on it. The evidence suggested that below more layers of earth and wood was an empty space—a vault containing chests, perhaps with gold coins inside. But these were just educated guesses, because no one could actually get down to them. Some attempts to widen or deepen the hole—or to get at the treasure indirectly through other holes—caused whatever the drill bits had hit to sink even farther down. The diggers eventually realized that the flooding was due to two or more horizontal tunnels that ran to the shore, and had seemingly been dug as booby traps. Unfortunately, repeated attempts to block those tunnels also failed. By the early 20th century, so many large holes had been created that the original location of the so-called money pit was no longer certain.

Excavations using modern equipment in the 1930s enlarged the main hole greatly, but still nothing of value was found. In the decades since, various groups have made additional attempts to unearth the treasure, digging ever larger and deeper holes, and although more intriguing objects have been uncovered, there’s still no definitive proof that there is, or was, a treasure there. Following years of legal disputes about the ownership of the land and the rights to any treasure that may be buried there, agreements were finally reached among various parties with a financial stake in the site and the provincial government. Excavation work is ongoing, and has been documented on the History Channel’s series The Curse of Oak Island since 2014.

Getting to the Bottom of It

Over the centuries, dozens of theories have been advanced as to what the Oak Island treasure really is. One popular theory holds that it’s Captain Kidd’s fortune—or that of some other pirate. Another says it’s the lost treasure of the Knights Templar. Some say (based apparently on that one tiny piece of parchment) that it’s Shakespeare’s original manuscripts. Others say it must be the Holy Grail. Although proponents of each of these theories make persuasive arguments as to why they must be correct, a recurring theme is that any treasure hidden so carefully and protected so elaborately as to defy two centuries’ worth of determined treasure hunters must be unfathomably important.

Except that it apparently wasn’t important enough for whoever hid it to come back for it—or pass on information of its whereabouts to anyone else.

And that assumes there’s something hidden there in the first place. There might not be. There is some evidence to suggest that the original “pit,” as well as the tunnels that fed water into it, were actually natural formations, and that the wooden “platforms” found at various points were nothing more than dead trees that had fallen into a hole once upon a time. What of the tackle block? And the gold chain? And the parchment? And the stone with the mysterious message? Well, all these artifacts have disappeared, and even if someone produced them, it would be impossible to prove they came from the pit. They could have been planted; they could also have been imagined. At no point in the last 200 years was work on the site controlled or documented carefully as an archeological dig would have been. All we truly have are the reports of people who wanted desperately to believe they were about to find a fabulous treasure.

Perhaps some day, when the best technology has been brought to bear on the problem (or there’s nothing left of the island but a gigantic hole), the Oak Island Mystery will be resolved once and for all. But we may ultimately find that the only real money on Oak Island came from a TV show.

Note: This is an updated version of an article that originally appeared on Interesting Thing of the Day on March 23, 2005.

Image credit: Richard McCully [Public domain], via Wikimedia Commons


Source: Interesting Thing of the Day

Elizabeth Tower

Big Ben and beyond

And now for something slightly different.

Years ago on my first visit to London, I took in many of the standard tourist attractions—dutifully snapping photos, reading the histories in the guide books, and so on. But I quickly realized that there was a disconnection between the kinds of things I find interesting and the kinds of things most tourists find interesting. Take Big Ben, for example. You can’t go to London without seeing (and hearing) Big Ben. It’s just one of those things. (And it’s a rather prominent feature of the skyline, too, so it would be difficult to avoid seeing even if you wanted to.) So we saw Big Ben. But other than having heard about it in children’s songs and stories since I was young, I couldn’t figure out what I was supposed to be so excited about. I’ve seen clocks. I’ve heard bells. Here’s one that’s larger than average. So?

It was not until well after I returned that I discovered a whole list of facts about Big Ben I hadn’t previously known. Although individually these facts are not extraordinarily impressive, I think that collectively they are rather interesting. If my British readers, for whom all of this is probably old news, will forgive me, I’d like to present a sampling of interesting things about the world’s most famous clock tower:

  • The part and the whole: For starters, contrary to common usage, Big Ben is actually the nickname of a single bell—not of the clock itself, the tower in which it is installed, or the building of which the tower is a part. The building is the Palace of Westminster, commonly known as the Houses of Parliament. The tower that houses the clock was previously known as the Clock Tower of the Palace of Westminster, but was renamed the Elizabeth Tower in 2012, in honor of Queen Elizabeth II’s Diamond Jubilee. The tower, in turn, houses the clock—officially known as the Great Clock of Westminster. It has four faces, one very large bell, and four smaller bells. The largest bell, which chimes on the hour—and which, by the way, is not visible from the outside—is the Great Bell of Westminster, or Big Ben for short. It was cast in 1856 and is one of Britain’s largest bells, at 9 feet (3m) in diameter.
  • For whom the bell is named: According to most accounts, Big Ben was named after Sir Benjamin Hall, Commissioner of Works at the time of the bell’s construction. Sir Benjamin was a large man, and so the nickname seemed appropriate given the size of the bell. However, others say the clock was named after champion boxer Benjamin Caunt. In either case, it was a man named Benjamin who had the nickname “Big Ben” first.
  • Cracks and replacements: The original specification for the clock had called for a bell weighing 14 tons. The foundry, however, made a much larger, 16-ton bell—which cracked during testing. So a different foundry was selected, and the original bell melted down as raw material for a second bell, which weighed 13.8 tons. This bell was thoroughly tested before being installed in the clock tower. After just one month in operation, though, the new bell also cracked—though not as severely as the first. The crack was filled, a lighter clapper installed, and the entire bell rotated so that the clapper struck an undamaged portion of the bell. This arrangement has survived ever since, but the crack affected the character of the bell’s tone as well as the pitch, which was originally an E.
  • The Liberty Bell connection: Whitechapel Foundry, where the (second and final) bell was cast, had also cast the Liberty Bell—which cracked on its first public ringing—almost exactly a century earlier, in 1752. By yet another coincidence, the Great Clock of Westminster famously broke down in 1976, the U.S. bicentennial year, requiring major reconstruction.
  • Accuracy: The Great Clock of Westminster is one of the largest mechanical clocks in the world—and, to this day, one of the most accurate. Its original specification stipulated that the first ring of the clock each hour should be within one second of the correct time. The leading clock designers of the day considered that an unreachable goal, because the hands and other exposed parts were subject to the action of wind, moisture, temperature changes, birds, and other variables that could easily throw off its accuracy by more than a second. However, after winning a design competition, Edmund Beckett Denison was hired to design the clock, which did in fact obtain the specified accuracy. When minor adjustments need to be made to regulate the clock’s speed, pennies are placed on the clock’s pendulum to alter its weight slightly.

Those who investigate the history of the clock’s design and operation will find many other fascinating facts, including any number of controversies and scandals that emerged during the years of its construction…and the presence of a prison cell in the clock tower, intended to hold Ministers of Parliament who have breached parliamentary privilege (though it has not been used for this purpose in over a century). All that to say, Big Ben is very much more than an oversized clock bell, but its most interesting features, like the bell itself, are nearly always hidden from public view.

Note: This is an updated version of an article that originally appeared on Interesting Thing of the Day on October 27, 2004.


Source: Interesting Thing of the Day