Great Mythconceptions Page 4
There are two mistakes here. First, it is the True Lemming that does the spectacular migrations, not the Collared Lemming shown in the documentary. Second, lemmings do not commit mass suicide. Instead, animals live to thrive and survive.
It’s funny that Disney could use a rodent called Mickey Mouse as their mascot (who in the early days, generated much of their income), but still be so unkind to another rodent, the lemming …
Boom and Bust
Up where the lemmings live, the locals have a saying, ‘Lemmings cycle, unless they don’t’. This saying is very true, and also symbolises that we still don’t understand why their population numbers go through boom-and-bust cycles. In a big year, lemming numbers can increase by a factor of 1000.
In 1924, the eminent British ecologist, Charles Elton, published an early paper describing how rodent populations varied wildly from year to year. Since then, ecologists have tried to understand why this occurs — with not a lot of success.
In October 2003, Olivier Glig (from the University of Helsinki) and his colleagues published their research. Over a 14-year window they looked at lemmings and their predators in the Karup Valley of Greenland. The population numbers followed a four-year cycle.
Three of the predators — Arctic Foxes, Snowy Owls and the Long-tailed Skua — migrated in and out of the area depending on the food supply, while the fourth predator — the stoat — stayed in the area. Glig’s mathematical model predicted that the population numbers of the migratory predators would exactly follow the population numbers of the lemmings — and this is what they found. They also predicted, and found, that the population peak of the stoats came one year after the population peak of the lemmings.
We are getting closer to understanding boom-and-bust population numbers in some animals.
References
Brook, Stephen, ‘Lemming myths takes fall’, Weekend Australian, 1–2 November 2003, p. 15.
Gilig, Olivier, Hanski, Ikka & Sittler, Benoît, ‘Cyclic dynamics in a simple vertebrate predator – prey community’, Science, vol. 302, 31 October 2003, pp. 866–868.
Hudson, Peter J. & Bjørnstad, Ottar N., ‘Vole stranglers and lemming cycles’, Science, vol. 302, 31 October 2003, pp. 797–798.
Moffat, Michael, ‘Do animals commit suicide?’, Discover, July 2002, p. 12.
Stitch
If you have ever done any strenuous exercise and pushed yourself really hard, you’ll probably have felt a ‘stitch’ — usually in the tummy. The Lack of Blood Theory of the stitch is fairly straightforward. It claims that because the exercise diverts blood to your arms and legs, there is less blood available for your central organs, especially the diaphragm muscle, which pulls your lungs downward so that you can breathe. The lack of blood causes the pain in your tummy, in much the same way that lack of blood to the heart muscle causes the pain of angina. Interesting theory — but it appears to be totally wrong.
The experts in this area — the exercise physiologists — don’t call this pain a stitch. They call it ETAP, or ‘exercise-related transient abdominal pain’.
The pain of a stitch usually happens in the abdomen, and most commonly, in the right upper quadrant near the liver. However, you can also get what athletes call a ‘shoulder stitch’. In fact, I consistently get it at the 10-km mark in the 14-km Sydney City-to-Surf Fun Run. People assume that once you become fitter, you stop getting stitches — but stitches happen to one-fifth of the extremely fit runners in the 67-km Swiss Alpine Ultra Marathon. About 80% of stitches are a sharp pain, while 20% are a dull pain. Usually the pain subsides a few minutes after you stop exercising, but occasionally it can last for two or three days.
One problem with the Lack of Blood to the Diaphragm Muscle Theory is that you can get a stitch while doing activities that do not involve a lot of laboured breathing, such as motorbike riding or the ever-popular pastime of camel riding. And in fact, during the practice for the invasion of France in World War II, soldiers who were subjected to rough jolting while standing still in torpedo boats suffered stitches.
This fits with the second theory for the cause of stitches — Mechanical Stress on the Visceral Ligaments.
The organs in your gut (between the bottom of your ribs and the top of your legs) are held in place by many different ligaments. This theory says that these ligaments get strained by the continual up-and-down pounding of the weight of the internal organs. This fits in with why you supposedly are more likely to have a stitch while exercising after eating a full meal. However, it doesn’t explain why one-fifth of expert swimmers still suffer from stitches. After all, there’s very little pounding as they power through the water.
But Dr Darren Morten, Director of the Avondale Centre for Exercise Sciences in New South Wales, has a third theory — Irritation of the Parietal Peritoneum.
The parietal peritoneum is a membrane that lines the entire gut cavity, including the bottom of the diaphragm muscle. Twisting your torso while swimming can irritate this membrane. A full stomach can also irritate your parietal peritoneum — in two separate ways. First, it places extra physical pressure on this membrane. Second, a full stomach sucks water into itself to aid digestion, dehydrating the parietal peritoneum. The Parietal Peritoneum Theory also explains the shoulder-tip stitch. Both the diaphragm near the liver, and the tip of your right shoulder, send their ‘pain’ signals to the same part of your brain. So you ‘feel’ some diaphragm pain as shoulder-tip pain.
So what can you do about a stitch? First, avoid doing strenuous exercise for at least two hours after a heavy meal. Second, avoid heavily sweetened drinks, and instead, drink isotonic fluids that have 6% carbohydrate.
References
‘Last Word’, New Scientist, 18 October 1999, p. 57.
Villazon, Luis, ‘What causes a stitch’, Focus, September 2003, p. 57.
Killer Aspartame and Diet Drinks
Aspartame, the common sweetener in low-calorie diet drinks, has not had an easy run since it was approved by the American Food and Drug Administration in 1981. Today, over 100 million people consume aspartame daily in over 1500 food products. However, the famous ‘Nancy Markle email’ blames aspartame for some 92 conditions ranging from headaches, fatigue, multiple sclerosis and systemic lupus erythematosis to dizziness, vertigo, diabetes and coma.
Aspartame is produced by combining two common amino acids — phenylalanine and aspartic acid. These amino acids are, like the other 18-or-so common amino acids, found in the proteins we eat and are part of our regular food intake. In aspartame, the phenylalanine has been modified by the addition of a methyl group chemical. The job of the gut is to prepare food so that it can enter the bloodstream. Because the aspartame molecule is too big to get into the bloodstream, the gut breaks it down into three smaller chemicals — phenylalanine, aspartic acid and methanol.
Like all good myths, this one has a germ of truth to it. Under certain circumstances, two of these chemicals (phenylalanine and methanol) can be poisonous.
The first chemical is the natural amino acid, phenylalanine. It is claimed that the phenylalanine is poisonous on the grounds that cans of diet drinks have a health warning: ‘Phenylketonurics: Contains Phenylalanine’.
Phenylalanine is in fact toxic to people with phenylketonuria, a very rare disease which affects one in 15 000 people. These people are usually diagnosed soon after birth with the Guthrie ‘heel prick’ test. In these people, phenylalanine is not broken down and can rise to toxic levels, causing brain damage. Phenylketonurics, placed on a special restricted diet to minimise their intake of phenylalanine, can live normal lives.
There is more phenylalanine in ‘regular’ foods than in diet drinks. For example, a can of diet drink has 100 mg of phenylalanine, an egg 300 mg, a glass of milk 500 mg and a large hamburger 900 mg. These are foods that phenylketonurics are taught to avoid. However, the other 14 999 people out of every 15 000 don’t have to worry about the toxic effects of phenylalanine.
The second chemical is the alcohol called meth
anol. (There are many chemicals in the alcohol family. Ethanol is the one that is good for us in small quantities — which is amazing for a chemical that can strip stains off a floor, and pickle and perfectly preserve small animals.) It is true that methanol in large doses is toxic. However, a can of diet drink will yield 20 mg of methanol, a very small dose, and easily handled by the body. Like phenylalanine, this chemical is found in our regular diet. A glass of fruit juice will give you 40 mg of methanol, and an alcoholic drink 60–100 mg.
There’s one final argument against the toxicity of diet drinks. None of the peer-reviewed medical literature shows a relationship between the consumption of diet drinks, and any of the 92 diseases that aspartame supposedly causes.
And what of Nancy Markle? She has never been found.
Aspartame
Aspartame is a low-calorie sweetener, which was invented in 1965. Weight for weight, it is about 200 times sweeter than sugar. It goes under many names — ‘Equal’, ‘NutraSweet’, ‘Spoonful’, ‘E951’ etc.
According to the US Food and Drug Administration, the ADI (Acceptable Daily Intake) is about 50 mg/kg of body weight per day. For a 75 kg person, this is the equivalent of 20 cans of diet drink per day.
It has remarkably few adverse reactions. Repeated studies have shown that it does not cause allergic reactions, headaches, cancer, epilepsy, multiple sclerosis, Parkinson’s disease, or Alzheimer’s disease. It does not affect vision, or cause changes in mood, behaviour or thought processes. It does not increase haemorrhagic risk, and it has no bad effects on dental health. On the other hand, some studies show that diet drinks with artificial sweeteners stimulate the appetite, which can lead to eating when you’re not hungry — which defeats the whole purpose of diet drinks.
Even the concern about the effect of heat on aspartame — e.g., when diet drinks are left in direct sunlight — seems ungrounded. No new toxic chemicals are created by the heat. The aspartame simply breaks down, and the taste of the drink becomes less sweet than before.
References
‘Kiss My Aspartame’, www.snopes.com/toxins/aspartame.asp: Urban legends reference pages.
Zehetner, Anthony & McLean, Mark, ‘Aspartame and the Internet’, The Lancet, vol. 354, 3 July 1999, p. 78.
The Black Box
The Black Box was a long time coming. In the early 1900s, the Wright Brothers invented a primitive device to record the revolutions of the propeller. By the late 1950s, this had evolved into the first flight data recorder, commonly called the Black Box. Whenever there is a plane crash, or a near crash, the highest priority of the accident investigators is to find the Black Box. Which isn’t black at all.
Since the 1960s, some 800 aircraft have been destroyed in crashes — and the Black Box has always survived. It came into existence because of the Comet, the first jet airliner. In 1953, Comet jets began to fall out of the sky — and nobody knew why. It took a lot of expensive testing to work out what had happened.
In 1957, an effort to make it easier to find the cause of a crash, the US Civil Aeronautics Authority proposed that all aircraft heavier than 20 000 lbs (about 9 tonnes) should carry a data-recording device. It would capture a few fundamental flight conditions of the plane, such as its direction, speed, altitude, vertical acceleration and time. Since then the technology has evolved from recording information on metal foil and steel wire to recording on magnetic tape. The latest generation has no moving parts, and records directly onto solid state memory.
The single Black Box has evolved into two Black Boxes. One of them is the CVR (Cockpit Voice Recorder) that can record up to two hours of the conversations and sounds in the cockpit. The latest FDR (Flight Data Recorder) can now record 24 hours of information about some 700 different aspects of the plane — such as oil pressure and rotation speed of all the moving parts in each of the engines, the angles of the flaps and the temperatures in the cargo hold. To give the Black Boxes maximum protection, they are located in the part of the plane that is usually last to hit the ground in a crash — the tail. The whole front of the plane is a crumple zone for the Black Boxes.
The latest generation of Black Box is tougher than the wrestlers of the World Wrestling Federation. The solid state memory is surrounded by aluminium, which is enclosed by super-efficient heat insulation material, which is then wrapped in a thick layer of stainless steel. The Black Box has to survive temperatures of 1100ºC for one hour, followed by 260ºC for 10 hours. In the crash impact test, it has to survive 3400 G of acceleration. Human beings will become unconscious if they experience 5 G for five seconds. The test is usually done by firing the Black Box out of a cannon. In the Pierce test, a 227-kg weight with a hardened steel spike, 6.5 millimetres in diameter, is dropped three metres onto the Black Box. A Black Box can survive the pressure at the bottom of the ocean, and being submerged in salt water for a month. All this high-end engineering means that a Black Box costs about $20 000–30 000.
Of course, the Black Box is not black. In 1965, it was changed to orange — a colour that can be easily spotted. We don’t really know why it is called a Black Box. A popular theory is that after a decent fire, the orange Black Boxes are indeed black, from the soot.
Why aren’t aeroplanes made to withstand the same forces as Black Boxes? First, in a crash, the crew and passengers would still not survive the G-forces. And second, the plane would be too heavy to fly.
Aussie Invention
In 1934, the father of 10-year-old David Warren was killed in one of Australia’s first air disasters. His last present to young David was a crystal radio set. David began building radios as a hobby, and so began a life-long interest in electronics.
In 1953, the first Comet crash happened. David was now a principal research scientist at the Aeronautical Research Laboratory (ARL) in Melbourne. He immediately realised that a recording of pilots’ voices and various instrument readings would provide invaluable clues as to the cause of the crash. He built the first Black Box, but could not engender any Australian interest in it.
In 1958, he got a lucky break. When the secretary of the UK Air Registration Board, Sir Robert Hardingham, visited ARL, David showed him his unofficial project. Sir Robert recognised its potential immediately and soon David Warren and his first Black Box were on their way to London. Various companies also saw its uses and built their own versions.
Black boxes became compulsory in Australia only after a Fokker Friendship crashed at Mackay in Queensland in 1960. In 1963, Australia became the first country to have a voice recorder in the cockpit.
References
Alpert, Mark, ‘A better Black Box’, Scientific American, September 2000, pp. 78–79.
O’Brien, John, ‘FYI’, Popular Science, March 2002, p. 79.
www.howstuffworks.com/black-box.htm
www.ntsb.gov/Aviation/CVR_FDR.htm
Duck Quacks Don’t Echo
In 2003, a popular myth — that a duck’s quack doesn’t echo — was scientifically debunked at Salford University in northwest England, at the annual meeting of the British Association for the Advancement of Science.
I was asked a question about this myth a few years ago on my science talk-back show on Triple J radio. I wasn’t able to answer it because I hadn’t read any research on the topic. However, on the face of it, it sounded like a ridiculous claim for three reasons.
First, each of the many species of duck has its own different quack. In fact, to make it more complicated, there are gender differences in quacks. For example, the female Mallard duck has a loud honking quack, while the male Mallard duck has a softer, rasping quack.
Second, most species of duck spend much of their time on the water — usually out in the open. Because there are not many hard reflective surfaces near most bodies of water, you don’t get many echoes, anyway.
Third, why should the quack of a duck (alone, of all sounds ever made on our planet) have some magical property that makes it echo-free?
Then a Triple J listener rang in with what the Intellige
nce Community calls ‘ground truth’. His family owned a duck farm, and he assured me that the quack of their ducks most certainly did echo off the walls of the sheds.
And this is where my understanding of ducks’ quacks rested, until Professor Trevor Cox from the Acoustics Research Centre at the University of Salford reported his research. The focus of his study was Daisy the Duck. There was nothing special about Daisy — Professor Cox just rang local duck farms until he found one (Stockley Farm) that would lend him a willing duck.
Professor Cox has worked with problems in sound for many years. For example, you’ve probably heard the sound from the loud speakers at a railway station echoing away until it’s almost unrecognisable. Professor Cox is the guy who can create a virtual prototype of a railway station inside a computer, and then adjust the design until you can hear the sound clearly. He can do the same for concert halls and even restaurants — in fact his work could save you from having to shout across the restaurant table just to be heard. And he’s also worked on using trees to absorb the sound of traffic and aeroplanes.
Being an expert in sound, he knew what to do with Daisy and her quack.
First, he got her to quack in an anechoic chamber — a specially designed room that deadens echoes. Her quack sounded like a regular quack, but a little softer than he expected.