Great Mythconceptions Page 5

  Second, he got Daisy to repeat her quack in a reverberation chamber, which artificially enhances the echoes. The quack did indeed echo — in fact, it sounded rather sinister.

  Third, he used a computer to simulate her quack in a concert hall — and sure enough, there was a small echo. And the same happened when he simulated Daisy’s quack as she flew in front of a virtual cliff inside his computer.

  But he noticed two odd things.

  First, Daisy’s quack didn’t finish sharply (like a hand clap), but tailed off softly. It faded away gently and gradually, making it hard to tell the difference between the original quack and the echo. Second, because her quack was actually quite soft, the echo was even softer. The combination of these two factors means that even if you do get an echo, it is lost in the tail end of the original quack.

  Professor Cox is hoping to use this knowledge to improve echo-ridden environments, such as railway stations and restaurants. And I guess that the original myth about the sound of the duck’s quack being echo-free is just quackers …

  Ducks Have Accents

  According to Dr Victoria de Rijke from Middlesex University ducks have different ‘accents’, depending on what kind of noise they are subjected to in their local area.

  Dr de Rijke lectures in English, with a special interest in phonetics (how language sounds to the ear). She is also the leader of the Quack Project. Her team records the sounds of children with different native languages (e.g. English, Vietnamese, Arabic and Tamil) copying the sounds of common animals, such as ducks.

  In an interview with The Guardian newspaper, she said, ‘London ducks have the stress of city life and a lot of noise to compete with, like sirens, horns, planes and trains. The cockney (London) quack is like a shout and a laugh.’ Therefore cockney ducks place their quack energy into the part of the sound spectrum where the background noise is quiet, so that other city ducks can hear them more easily. Dr de Rijke continued, ‘On the other hand, the Cornish ducks have a big field to roam in and their quiet surroundings make all of a difference. The Cornish ducks made longer and more relaxed sounds, much more chilled out. They sound like they are giggling. So it is like humans: cockneys have short and open vowels, whereas the Cornish have longer vowels and speak fairly slowly.’

  She now plans to study ducks’ quacks in Newcastle, Liverpool and Ireland.

  References

  ‘I’m a duck, me old cock sparrer’, Sydney Morning Herald, 5–6 May 2004, p. 19.

  Radford, Tim, ‘Scientist proves echo claim is just plain quackers’, Sydney Morning Herald, 18 September 2003.

  Switch on Light Bulb

  An enduring childhood memory is being told by your parents not to keep turning the electric light switch on and off. Supposedly ‘each time you switch the light on, you burn up enough power to run the light bulb for 30 minutes’. And in retaliation, many cheeky kids would deliberately wait until their parents left the room and then flick the switch hundreds of times to send their parents broke.

  However, once you start doing the calculations, you realise that this is a ridiculous claim.

  Enclosed inside the average light bulb is a thin wire made of silver-coloured metal called tungsten. When the tungsten is cold, it has a very low resistance to electricity. As soon as you flick on the light switch, a huge number of electrons flow through this thin wire which heats up very quickly, and starts to glow — first yellow, and then red and finally white. As it heats up, the resistance increases, reducing the numbers of electrons flowing in the wire. (The number of electrons tells you the current — more electrons means more current.) Within one-fifth of a second of start-up, the light has come up to full brightness, and the electrical current stabilises at a steady value.

  When your parents told you to stop flicking the switch on and off, they were probably thinking about this initial surge in electricity. But how big is this surge? Is the number of electrons that flow in this first fifth of a second equal to the number of electrons that flow in 30 minutes of normal running?

  Suppose that your parents were indeed correct about the surge of current in the first fifth of a second being equal to the current used in 30 minutes. There are 1800 seconds in 30 minutes. During the fifth-of-a-second start-up, your light bulb would have burnt 1800 x 5 = 9000 times the average power consumption of your light bulb. If you have a 100 watt light bulb, then each time you switch on the light, you burn 900 000 watts, or nearly a megawatt of power. Mind you, that would be for only one-fifth of a second. This is roughly the power output of a very small power station. A sudden drain of this much power would vaporise the wires in your house, and make the lights dim in your suburb or town.

  In fact, this initial surge of current would probably burn up one-tenth of a second’s worth of regular electric light burning — or perhaps a maximum of one second. On the other hand, your parents were right about so many other things — such as the need to eat lots of vegies, and to have a good night’s sleep.

  History of Light Bulbs

  The light bulb could have been invented in 1666 — if somebody had seen the light. This was the year of a giant storm in London. One night, lightning hit St Paul’s Cathedral so frequently, that the thick copper straps carrying the electricity down to the ground from the lightning rods on the roof glowed a dull red colour — just like an electric light bulb starting up.

  In 1801, Sir Humphry Davy ran electricity through strips of platinum, and they glowed — but not for long. In 1841, Frederick de Moleyns (also in England) generated light by running electricity through powdered charcoal, and obtained the first patent for an incandescent bulb. Again, his bulb didn’t last long.

  The secret was keeping oxygen (in the air) away from the hot glowing material — and this needed the invention of good vacuum pumps. It was a close race between Sir Joseph Wilson Swan (England, 1878) and Thomas Alva Edison (United States, 1879), who each came up with carbon filaments. But Edison got all the credit, perhaps because he had developed the other technology (e.g. power plant and transmission lines) needed to have a practical lighting system. Today, the bulbs contain an inert gas and the inside of the bulb is not a vacuum.

  Faster Light Bulbs

  Light bulbs with a faster reaction time are making it safer for car drivers who are braking behind you.

  The normal light bulb in the brake-light circuit of your car is very similar to the incandescent light bulb of 1911, when tungsten filaments were introduced. You hit the brake pedal with your foot, making electricity flow into an incandescent light bulb at the rear of your car. After a short delay to heat the tungsten wire to white hot, the bulb reaches full brightness. Only then does the driver behind you realise that you have hit the brakes — and only then do they start the process of hitting their brakes.

  A relatively new innovation is the use of the red LED (Light Emitting Diode) in the brake-light circuit. The red LED emits light within a millionth of a second after the electricity hits it. Compared to an incandescent bulb, it has no significant time delay. This means that the person following can see the brake light come on sooner, which at 60 kph, means that they get a braking distance of a few extra metres.

  References

  Mills, Evan, ‘Eleven energy myths: from efficient halogen lights to cleaning refrigerator coils’, Science Beat, Berkeley Lab, 24 April 2001.

  Sydney Morning Herald, Good Weekend/Spectrum, 18 August 2003, p. 22.

  www.lbl.gov/Science-Articles/Archive/energy-myths3.html

  Cat Years

  Many of us own a cat. In fact, about one in every three Australian households owns one. A cat’s age is often measured in human terms, that is, one cat year is equal to seven human years. This standard myth might make the maths nice and simple, but the reality is much more complex.

  The average life expectancy for the domestic cat is about 14 years, but for the feral cat it’s closer to two years (due to road accidents, infectious diseases, poisoning, etc.). The maximum life expectancy of a cat is around 20–22 years, alth
ough one domestic cat was reported to have lived for 34 years.

  Three main factors affect the maximum life span of an animal. The first factor is intelligence — the smarter the animal, the better it can adapt to its environment, and survive any hazards. The second factor is the environment and its associated hazards. In the wild most animals are killed by accidents or natural predators, well before their agility decreases as a result of ageing. The third factor is nutrition — too much or too little food will shorten the animal’s life span.

  The Feline Health Center at Cornell University in the United States advise that cats reach the young adult stage at 18–24 months (whereas human beings take about 22 years to reach this stage). Therefore a cat that is one calendar year of age is about 16 cat years of age. Curiously, one more calendar year adds another six cat years — roughly equivalent to 22 human years. And after that, you simply add four cat years for each calendar year. So a four-year-old cat is the equivalent age of a 30-year-old person, a 10-year-old cat the equivalent age of a 54-year-old person, and a 20-year-old cat would be 94 cat years of age.

  The scale is roughly the same for dogs, but with one major difference. In general, the larger the dog, the younger it is when it dies. For example, a Great Dane would be old at nine calendar years of age, while a Chihuahua would be considered ‘old’ at 15 calendar years of age.

  However, for both cats and dogs, the simple calculation — one calendar year equals seven pet years — is definitely a mythconception. Think about it. There are many 12-year-old cats that can jump tall fences and chase other cats — but you won’t see similar behaviour in most 84-year-old human beings.

  Egyptian Cats

  In ancient Egypt the cat had great religious significance. The ancient Egyptians mummified dead cats and placed them in tombs.

  In the 19th century, many amateur archaeologists were running wild across Egypt. They found so many dead cats in the tombs, that they just threw them away. The mummified cats were used for fertiliser and as ballast on ships.

  Recent x-rays of these cats found that most of them did not die of old age. In fact, these mummified cats were only a few months of age, and were all in good health until they were strangled. The theory is that the cats were bred by priests in the temples, and then killed and mummified, to be sold to temple visitors or tourists as votive offerings.

  Of course there were different grades of mummies — a well-wrapped ones fetched a higher price.

  References

  Brace, James J., ‘Theories of ageing: an overview’, Veterinary Clinics of North America: Small Animal Practice, November 1981, pp. 811–814.

  Thrusfield, M.V., ‘Demographic characteristics of the canine and feline populations of the UK in 1986’, Journal of Small Animal Practice, 1989, pp. 76–80.

  No Lead in the Pencil

  We have been using lead, a grey or silver-white soft metal, for thousands of years. Although lead has many useful properties, it is, unfortunately, also quite toxic to human beings. As a result, lead has been replaced, in many applications, by less toxic metals. Even so, many people still believe the mythconception that lead pencils contain lead.

  For tens of thousands of years, our ancestors drew on cave walls with pieces of charcoal or sticks. About 3500 years ago, during the 18th Dynasty in Egypt, the technology had advanced from burnt sticks to a thin paint brush around 15–20 cm long. The brush made a fine, wet dark line. About 1500 years later, the Greeks and the Romans realised that a sharpened lump of lead would mark papyrus with a dry, light line.

  Another 1500 years later, during the Middle Ages, European merchants commonly used a metal stylus (called a ‘metalpoint’) which could make faint marks on paper. The merchants made these faint marks more visible by first coating the surface with a material like chalk. If the metal were lead — it usually was — it would mark the fingers, so it was often wrapped in paper, string or wood.

  The beauty of the modern pencil is that it combines the best qualities of the paint brush and the lump of metal in one product. The modern pencil makes a line that is very useful because it is both dry (so that it doesn’t run) and dark (so that it’s easy to see).

  The modern lead-free lead pencil first appeared in the early 1500s, in Borrowdale, in the Cumberland Lakes District of England. Legend has it that when a large tree blew over, the local shepherds noticed a black material clinging to the roots. They tried to burn it, thinking that it was coal — but it would not burn. However, they quickly found a use for it — marking their sheep.

  The shepherds had discovered graphite, which is actually a variety of carbon. But at the time they thought it was just a variety of lead, so they called it ‘black lead’.

  We know that black lead was not commonly used in pencils up to 1540, because in that year, the Italian writing master, Giovanbattista Palatino, wrote a book describing what he thought would be ‘all the tools that a good scribe must have’. It did not include anything that looked like a pencil, or contained graphite. But 25 years later, in 1565, Konrad Gesner, a Swiss naturalist and physician, wrote a book on fossils. In his book, he describes and makes a drawing of a new writing instrument that seems to be the first primitive black-lead pencil. Lead pencils were now becoming common.

  In 1609, a character in Ben Jonson’s play Epicoene describes some mathematical instruments including ‘his square, his compasses, his brass pens, and black-lead to draw maps’. In 1622, in Nuremberg, Friedrich Staedtler became the first person to mass-produce pencils. In 1683, Sir John Pettus wrote a book on metallurgy in which he noted that the Borrowdale mine produced a type of lead, which was exploited by painters, surgeons and writers. Painters drew their preliminary sketches with it, surgeons used this black lead as a medicine, while writers rejoiced in this new instrument that freed them from having to carry a bottle of ink.

  For a few centuries after its discovery, the Borrowdale black lead remained the highest quality deposit ever found. Besides its medical, painting and writing applications, graphite had very important strategic military functions in casting cannon balls and other metal objects. Therefore, on 26 March 1752, the House of Commons passed a bill entitled, ‘An Act for the More Effectual Securing Mines of Black Lead from Theft and Robbery’. This Act made it a felony, punishable by hard labour and/or transportation to the colonies, to steal this high quality graphite.

  For many years the English would not allow their enemies to use the pure Borrowdale graphite. It was not until 1795, through the urging of Napoleon, that Nicolas-Jacques Conté finally worked out a method of converting low quality graphite into a fine writing material. He ground low quality graphite very finely, mixed it with finely ground clay, fired the mixture at high temperatures, and finished by adding wax before inserting it into slim wooden cases. In 1832, a pencil factory started operations near the Borrowdale graphite supply. In 1916, it became the Cumberland Pencil Factory, which produced the Derwent pencils still loved by school children.

  However, although writing pencils made of graphite were first used around 1565, writing pencils that used lead were still very commonly used in the 18th century. Why? Because they were cheaper, even if they were toxic. You certainly wouldn’t want to suck on a ‘lead’ pencil if it really had lead in it. In fact, lead pencils became extinct only in the early 20th century.

  The modern lead pencil is very good technology. It is entirely self-contained, uses no messy liquids such as ink, can write a continuous line for some 35 km, makes a well-defined mark that is relatively smudge-proof and is easy to erase.

  Today we have glasses made of plastic, tins made of aluminium and golfing irons made of titanium. So it really shouldn’t bother us that lead pencils use graphite.

  Forms of Carbon

  It was only in 1779, that the Swedish chemist K.W. Scheele proved that the Borrowdale black lead was not lead, but in fact a form of carbon. It was given a new name, ‘graphite’, which comes from the Greek verb graphein, ‘to write’.

  Graphite is a variety of carbon
which is the sixth lightest element, fitting between boron and nitrogen. It is not very common in the Earth’s crust (making up 0.025% by weight), but it makes more chemical compounds than any other element.

  There are three forms of pure carbon — when it exists as pure carbon, and is not combined with any other element.

  Diamond, which is the hardest element known, is made up of carbon atoms arranged in a series of tiny pyramids.

  Another form is called ‘buckyballs’, where the carbon atoms (typically 60, but there can be more or fewer than 60) are arranged in a hollow ball, like a soccer ball. ‘Buckytubes’ or ‘nanotubes’ are very similar — and are carbon atoms arranged in hollow tubes, like a drinking straw. Buckyballs and buckytubes are very strong.

  In graphite, the carbon atoms are arranged in circles of six that are joined, side by side, to make thin sheets. These thin sheets are stacked on top of each other. The chemical bonds are very strong within each sheet — but are very weak from one sheet to the next. This weak joining makes the sheets easy to slide over each other, making graphite an excellent lubricant. The weak joining also means that when you wipe graphite over a slightly rough surface like paper, a few of the sheets rub off, leaving a mark on the paper. Graphite is also one of the softest known minerals.

  Penis to Pencil

  The word ‘pencil’ comes from the Latin word penicillum, which was a collection of fine animal tail hairs that had been shoved into a hollow reed. It got its name from peniculus, which was the Latin word for ‘brush’. In turn, the ‘brush’ got its name from the Latin word penis, which meant ‘tail’— the location on the animal from which you plucked the hairs.