Family line
My wife’s parents have six children, the first three and the sixth of whom are girls. Four of these children have children of their own, seven in all, and all of them girls. I am aware that men in certain occupations are more likely to father girls, but in this family the seven grandchildren have four different fathers. Is this purely coincidence, or are there other factors at work?
Mark Higgins
Glasgow, UK
Without knowing all the details, I will venture that coincidence seems likely. Any foetus has approximately a 1-in-2 chance of being female; the chance of seven children all being girls is therefore 1 in 2 to the seventh power, or 1 in 128. These are not particularly long odds, and if you consider that one would probably find several other combinations remarkable too (all boys, for example, or exactly alternating girls and boys), the odds that any given set of six grandchildren will exhibit a ‘remarkable’ pattern is low enough that such an occurrence is, in fact, unremarkable.
This question stems from the human ability to find patterns in random data. It has been observed that people’s expectation about what a random sequence looks like are actually quite different from a typical random sequence. With coin flips, for example, a person might cite ‘HTHHTHTTHHHTTH’ as a typical sequence, but a truly typical random sequence might look more like ‘HHHHHTHHTTHHHH’: less alternation, longer runs of one value, and a ratio of heads to tails that is often far from 0.5 for short sequences. This means, conversely, that sequences that actually are random often appear not to be random to most people.
If the group eventually reached 15 grandchildren and all were girls, then I might raise an eyebrow and wonder whether there might be a non-random cause at work. But even here the probability is still low enough (1 in about 32,000) for it to have happened quite a few times by chance throughout history.
Ben Haller
Menlo Park, California, US
Cold surface
I have heard that a common way to catch a cold is if somebody with the virus touches your hand before you touch your own nose or eyes. Apparently it can even be passed on via a third surface such as a door handle. How long can a cold virus or any other pathogen live on a surface? Does it depend on the surface and does moisture make a difference?
Cory Caulfell
Washington DC, US
It depends on the surface. Cool, moist glass in the shade, for instance, might retain many kinds of rhinovirus or coronavirus for days.
Brass which is dry, sun-baked and covered with verdigris and zinc compounds, on the other hand, might be germ-free within half an hour of being touched. Such compounds are bad for most microbes, so filthy lucre, especially coins made of copper alloys, is not nearly as horribly germy as one might expect.
By and large, rhinoviruses are the most common causes of colds. They are picornaviruses, which are generally only moderately stable. Desiccation and ultraviolet light in open sunshine should render most surfaces safe quite quickly. A cosy damp pocket handkerchief, though, might harbour the germs for days, unless it is infested with decay bacteria that digest viruses along with the nutritious secretions donated by the owner.
To avoid infection in a viral epidemic, it makes sense to avoid touching your face as far as possible and to wash your hands before doing so.
Jon Richfield
Somerset West, South Africa
Killer chemical
How does chlorine in swimming pools kill harmful organisms, and why is it the chemical of choice?
Tommy Krone
Copenhagen, Denmark
Chlorine is not the only member of the halogen group that can be used to disinfect water; iodine and bromine will also do the job, though not fluorine because it is too reactive. Chlorine is often chosen simply because it is cheap, readily available and relatively easy to handle.
Disinfection relies on disrupting a harmful organism’s metabolism or structure. That can be achieved by oxidation and non-oxidising chemicals which have similar effects, as well as by non-chemical processes such as ultraviolet (including sunlight), X-rays, ultrasound, heat (as in pasteurisation), variations in pH and even storage to allow organisms to die naturally.
Chlorine gas consists of molecules of two chlorine atoms but no oxygen. When added to water, one of the atoms forms a chloride ion. The other reacts with water to form hypochlorous acid, an oxidising agent. Disinfection comes from the hypochlorous acid reacting with another molecule, most probably in the bacterial cell wall, in an oxidation-reduction reaction. If this happens enough times, the organism’s repair mechanisms are overwhelmed and it dies. So concentration of disinfectant and the length of time pathogens are exposed to it are important factors.
Chlorine is available in many different chemical forms, such as chlorine gas, sodium hypochlorite powder (often used in home swimming pools), and chlorinated lime or bleaching powder. Some chemicals containing chlorine are not disinfectants because the chlorine in them, usually in the form of chloride, is completely reduced with no further oxidising power. Sodium chloride is such a chemical, which is why water cannot be disinfected using a pinch of salt, and why pathogens can survive in seawater.
Philip Jones
Water Environment Consultants, Woking, Surrey, UK
Disinfection needs to be carried out under closely controlled pH conditions, ideally between 7 and 7.6. If the pH is too low – less than 6.8 – there is a tendency for nitrogen compounds, especially urea (a common pool contaminant) to degrade via another route to chloramines. The worst of these is nitrogen trichloride, which irritates the eyes and creates the so-called chlorine smell associated with poorly run or overused swimming pools.
Philip Stainer
Lach Dennis Consultants, Haverhill, Suffolk, UK
Chlorination removes contamination immediately in the pool, whereas ultraviolet and ozone treatment work in the plant room. All these systems also use filters to remove organic matter. The less turbid the water, the lower the dose of chlorine needed to sterilise it. So a constant, low level of chlorine can be maintained in the water circulating between pool and plant room, and it can be altered as pool users and pollution levels vary.
Lois Vickers
Bideford, Devon, UK Thanks also to Roger Cole of Proton Water Services
Pipe dreams
During a conversation about playing the bagpipes at high altitude, I wondered what would happen to the sound of the bagpipes if they were played in the helium/oxygen mix used by deep sea divers, which distorts speech. Would the double reed chanter (the output part of the bagpipe that consists of a tube with holes and is played with the fingers) be affected in the same way as the single-reed drones (the output pipes confined to single notes)?
Roger Malton
Errol, Tayside, UK
The construction of a bagpipe allows a continuous supply of air to be maintained. A flexible bag is filled with air and acts as a reservoir. By squeezing the bag while a breath is taken, the flow of air can be kept up in both drone pipes and chanter.
The fundamental frequency of a resonating cavity, whether it is the voice or a resonating tube like a bagpipe chanter, is directly proportional to the speed of sound of the gas occupying the cavity. The speed of sound is proportional to the square root of T/M (where T is the absolute temperature of the gas and M is its molecular weight). Therefore the speed of sound is higher in gases with smaller molecular weights. For example, the speed of sound in air (where M = 28.964) at 0 °C is 331.3 metres per second. And in helium (where M = 4.003) the speed is 891.2 metres per second. The resonance frequencies of the vocal tract are therefore almost 2.7 times higher for helium than for air and the pitch will be much higher than usual, rather like Donald Duck’s.
The original question is, of course, the wrong one. It is difficult to imagine playing the Scottish bagpipe in the confines of a diving bell filled with the helium-oxygen mix. The question is more relevant to the Irish whistle which is easily portable and still satisfies a deep-seated human need for Celtic music.
I carried out an experiment by inhaling from a toy helium balloon with my brass Sindt D whistle 41 metres above sea-level, where the ambient temperature was 22 °C. Once a stable note had been reached, the pitch jumped up almost exactly three semitones from D to F and remained in tune from then on. Although I had to blow harder to keep the notes constant I could play the first 12 bars of ‘Down by the Sally Gardens’ without taking a breath, albeit slightly faster than usual. The air/helium mix I exhaled after taking the first breath of air returned the pitch to D sharp. However a pure D did not return for some time as residual helium was slowly cleared from my lungs. Residual lung volume accounts for about 25 per cent of total lung volume, therefore the first breath of helium was probably about 75 per cent mix, and the second approximately 18 per cent, assuming that the gas inhaled from the balloon was pure.
Tony Lamont
Brisbane, Queensland, Australia
The pitch of both types of pipe in the bagpipes is determined by the effective length of the pipe (which is varied by opening holes in the chanter) and not by the reed. The reed adapts its frequency to the resonance set up in the pipe in which it sits. The frequencies of the modes of any pipe are proportional to the velocity of sound in the gas and, because this is much higher in helium than in air, the pitch of the bagpipes must rise.
I used to teach the physics of music to opera singers at a major music college, and they were always impressed when I took along a helium cylinder and had them fill their vocal cavities and lungs with it. When you do this you need to be careful to retain some carbon dioxide in your lungs because this stimulates the automatic breathing reflex. In the case of singers, the pitch does not in fact change, because it is determined by the vocal cords, not the pipe.
The resonances are not strong enough to dominate the heavy vocal cords and their di-muscular control. What does change is the frequency of every resonance of the vocal tract, and hence the tone colour (actually, the formant) of the voice changes dramatically. The voice sounds higher because the colour shifts to higher frequencies, not the actual pitch.
In practice, very few singers managed to hear much of their new voice, because they invariably laughed at the unfamiliar sound they produced and quickly expelled the helium.
John Elliot
UMIST, Manchester, UK
Yes, bagpipes do work with helium or helium mixtures – 100 per cent helium in the bag raises the pitch by about an octave and some retuning is required between chanter and drone.
Trials were done with bagpipes as a precursor to designing the heli racket, an instrument entered in the new musical instrument challenge run by BBC2 TV programme Local Heroes. Helium and air were blown through a bagpipe chanter, and notes changed by varying the ratio of gases using a mixing valve (in this case, a bathroom tap), rather than finger holes. The instrument gave a passable televised rendition of ‘Twinkle Twinkle Little Star’.
As an alternative to helium, mixtures of gases heavier than air, such as oxygen and neon, could be used to lower the pitch.
I can also report that changes of gas do nothing for tone quality.
Mark Williams
Winchester, Hampshire, UK
The resonant frequencies of all pipes and air chambers are directly proportional to the speed of sound. A helium/oxygen mixture will increase all the frequencies but carbon dioxide will have the reverse effect, so musicians beware.
Woodwind players know that they must avoid drinking fizzy drinks before performances. If you belch into the instrument as you play it, you fill it with carbon dioxide which has a lower sound velocity.
The instrument goes horribly flat and doesn’t recover its pitch until all the carbon dioxide has been blown through. Changing from pure air to pure carbon dioxide would send the instrument about seven semitones flat.
Laurie Griffiths
By email, no address supplied
In response to the question asking whether bagpipes sound better if played with a mixture of helium and oxygen instead of air: of course not, bagpipes already sound perfect.
Joe Boswell
Aberdeen, UK
Received pronunciation
How do accents develop and change? More specifically, how do new accents form, such as those that arose in Australia and New Zealand? Presumably these are no more than 200 years old.
Ciaron Linstead
Plymouth, Devon, UK
Accents and dialects develop and change for two distinct reasons, one phonetic, the other social. On the phonetic side, speech sounds change because of the way they are produced and perceived. Feel the position of your tongue against the roof of your mouth when you say the K sounds at the beginning of ‘key’ and ‘car’. The tongue makes contact farther forward in ‘key’ than in ‘car’, because it is anticipating its forward position for the vowel sound EE. This more forward position has led to changes in which K sounds became CH or SH or S sounds before EE or E vowels. The Latin word centum began with a K sound, but Italian cento begins with CH and French cent with S. These changes were among many that occurred as Latin evolved into modern Romance languages.
Phonetic changes don’t happen continuously, though, because language is used to communicate. If your pronunciation is suddenly different from that of the people around you, you won’t be understood. The communicative function of language provides a social brake on the phonetic causes of change. In any community, however, phonetic changes can take hold from one generation to the next. When communities are relatively isolated as Australia was from England during its development they may adopt different phonetic changes. This is how Australian and English pronunciations have diverged. Two hundred years is plenty of time for differences to develop.
This kind of divergence brings a more subtle social effect into play. The information you convey when you talk is not limited to the linguistic meaning of your words, but includes many things about yourself, such as regional origin or level of education. Speakers unconsciously (or consciously) tailor their speech to sound like the person they want to appear to be. This has an influence on the development of accents and their change: people adopt or reject specific sounds and sound changes to signal their identification with a particular community.
Bob Ladd
Professor of Linguistics
University of Edinburgh, UK
Starting with a relatively uniform speech community, minor variations in sounds may acquire greater or lesser prestige by association with individuals or groups who use them.
In Australia and New Zealand, the biggest divergence from English ‘standard received pronunciation’ is in the vowel system. In the early 19th century, there was a tendency in southern England, where many colonists came from, to pronounce the vowel in ‘bad’ (known to phoneticians as RP Vowel No 4 or RP 4) in a more ‘closed’ position (with the mouth less open) so it sounded more like ‘bed’. Later, this trend was halted and partially reversed in England. Its southern base was relatively stagnant demographically compared with the booming North and Midlands, which kept the more open A in ‘bad’. Today, the very closed version of vowel 4 is increasingly stigmatised as ‘hyperposh’ and causes surprise when heard in old 1940s newsreels.
By contrast, in Australia and New Zealand it flourished, perhaps cementing solidarity among the older settlers as against the later-arriving Poms, who had the more open vowel. The ‘closedness’ was exaggerated further, causing potential confusion with RP 3, as in ‘bed’. The latter vowel had to move over to make room for it, by becoming even more closed and sounding like ‘bid’. The vowel in ‘bid’ (RP 2) in turn had to become still more closed, to sound like RP 1 ‘bead’, which in turn tended to become a diphthong, sounding something like ‘buyd’. In New Zealand, the process was similar, except that RP 2 (‘bid’) was pushed into the centre of the mouth, to sound like RP 10 as in ‘bud’ or RP 12 – the sound in the second syllable of ‘cupboard’.
This phonetic musical chairs, caused by an initial point of imbalance in the system, is known to linguists as a ‘push-chain’. RP 4 ‘pushed’ the others to make room for itself.
There can also be a ‘pull-chain’ in which a departing vowel leaves a slot into which a neighbouring sound can expand. This also happened in Australia. Once RP 4 ‘bad’ had moved over to ‘bed’, the long back-vowel of ‘bard’ RP 5 was free to drift to the front of the mouth, without fear of confusion.
Thus, RP 4 has ‘pulled’ RP 5 after it. In support of this, in Australian soaps like Neighbours, older characters tend to have accents closer to received pronunciation, but younger ones have a pronunciation typical of the system outlined here.
Steve Tanner
Carmarthen, UK
It is often assumed that accents in countries that see large-scale immigration will diverge from the accents of the settlers’ original country. The reverse may be true, however. The original accent can remain in the country now occupied by immigrants, while the accent in the nation of origin develops along new lines. This has occurred in the development of American English.
The first permanent English immigrants to North America settled in Jamestown, Virginia, in 1607, while 13 years later the Pilgrim Fathers landed further north at what is now Plymouth, Massachusetts. The Cambridge Encyclopaedia of the English Language by David Crystal tells us that these two settlements had different linguistic consequences for the development of American English. The Jamestown colonists came mainly from England’s West Country and spoke with the characteristic burr of these counties. This pattern can still be heard in some of the communities of the Jamestown region, especially Tangier Island in Chesapeake Bay. Because of the relative isolation of this area, this ‘Tidewater’ accent has changed only slightly in 400 years and is sometimes said to be the closest we will ever get to the sound of Shakespearean English.
The Plymouth colonists, by contrast, came from eastern England. These accents dominated in what is now New England, and their speech patterns are still the main influence in this area. An outline of the development of English in all its forms can be found on the BBC website www.bbc.co.uk/routesofenglish — Ed.
War nuts
An entry in the local school logbook for the village of Nash in north Buckinghamshire, dated 9 November 1917, states ‘Letter of thanks received from the Director of Propellant Supplies for chestnuts gathered for the making of munitions’.
John Harris and Greg Davies
Milton Keynes, Buckinghamshire, UK
We have had visions of chestnut shrapnel, but this can’t be right, can it? So what were chestnuts used for and what is their link with propellants? — Ed.
This question was asked in the February 1987 issue of Chemistry in Britain, the Royal Society of Chemistry’s monthly magazine. Subsequent correspondents gave the answer that the chestnuts were used in the First World War for the production of acetone which, in turn, was needed for the production of cordite, the smokeless powder used as propellant in small arms ammunition and artillery.
Smokeless powders such as cordite had changed the face of battle. They offered longer range than ‘black powder’, better known as gunpowder. Producing only a faint blue-grey haze, they permitted machine guns to fire without obscuring the gunner’s view and they permitted snipers to operate without revealing their position. Cordite is a mixture of the explosives guncotton (65 per cent), nitroglycerine (30 per cent) and petroleum jelly (5 per cent), gelatinised with the aid of acetone before being worked into threads for use.
Prewar techniques for large-scale acetone manufacture were inadequate to meet the demand during the First World War. As minister of munitions, David Lloyd George appointed Chaim Weizmann, a chemist who had emigrated from mainland Europe in 1904, to increase acetone production using a process of his own invention involving the bacterial fermentation of maize starch. Factories at Poole in Dorset and King’s Lynn in Norfolk produced up to 90,000 gallons of acetone a year. When supplies of maize ran short, it was supplemented as a source of starch with horse chestnuts, collected by schoolchildren. Since the factory locations were withheld for the sake of security, the schools addressed their parcels to government offices in London, but workers at the General Post Office apparently knew to send them directly to the factories.
This is how Lloyd George’s acetone problem left traces in school record books. It also left, in his own words, ‘a permanent mark on the map of the world’. Lloyd George was so grateful to Weizmann, an ardent Zionist, that on becoming prime minister he gave Weizmann direct access to the foreign secretary, A. J. Balfour. The result was the famous and controversial ‘Balfour Declaration’ of 2 November 1917, stating that the British government viewed with qualified favour ‘the establishment in Palestine of a national home for the Jewish people’. When the state of Israel came into existence, Weizmann was elected as its first president in 1948 and held that position until his death in 1952.
Michael Goode
Harwell, Oxfordshire, UK
Tony Cross, who is the curator of the Curtis Museum in Alton, Hampshire, drew our attention to similar school records from his own area and to an explanation he received for them from the Imperial War Museum. The answer below summarises that explanation — Ed.
During the First World War some 258 million shells were used by the British Army and the Royal Navy. The basic propellant used to fire these shells, and for a whole host of other military purposes, was cordite. The solvents used in manufacturing cordite were acetone and ether-alcohol.
Acetone was produced almost entirely by the destructive distillation of wood, for which the world market was dominated by the great timber-growing countries. Before the war acetone was mainly imported from the US. In 1913 a modern factory was established in the Forest of Dean but, by the outbreak of war in August 1914, the stocks of acetone for military use stood at only 3200 tons. It was soon apparent that production would not meet the rapidly growing demand. When it was discovered that acetone could be produced from potatoes and maize, new factories were erected to undertake this work.
By 1917, however, the German submarine offensive in the Atlantic had caused a shortage of freight which threatened to cut off supplies of North American maize. With the possibility of a serious maize shortage, experiments began to find a substitute and it was discovered that the horse chestnut could be used as an alternative in acetone production. Vast quantities of horse chestnuts were collected, but only 3000 tons reached the King’s Lynn plant. Collection was restricted by transport difficulties, and letters in The Times tell of piles of rotting horse chestnuts at railway stations.
After initial production difficulties the King’s Lynn factory began production of acetone from horse chestnuts in April 1918. Work was hampered by the fact that the horse chestnut was a poor-quality material from which to produce acetone. The plant was eventually closed in July 1918.