Raising the roof
A warning to anyone tempted to throw paint on their roof to cool their house (“White paint on a hot tin roof”, 25 March). First check the substratum of the roof on which your asphalt tiles are laid. This is usually wood. An asphalt tile roof must “breath”.
As I discovered to my cost a couple of years ago, roof paints seal the roof, and consequently condensation beneath the tiles will quickly rot the wooden substratum.
The cooling effect of white roofing paint is not doubted. I measured the temperature drop with external air temperatures in the mid-nineties (Farenheit) of some 10 degrees. But the cost in terms of a new roof after little more than a year 鈥�
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Thrashing managers
The removal of David Bishop from Oxford’s Institute of Virology was indeed startling (Letters, 22 April).
The explanation is given by Ian Stewart in his article on juggling (“Juggling by numbers” 18 March): “It has been known for a long time that control systems can behave chaotically 鈥� if they are ‘over driven’ 鈥� The entire system thrashes, spending nearly all of its time reacting to its own errors and very little time reacting to the reality it is supposed to be controlling.”
The burgeoning numbers of managers in our research establishments ensure that this kind of thing is going to happen increasingly often.
Many wives
Re Kate Charlesworth’s “Life, the Universe and (almost) everything” on “Boffin lurve” (29 April): I doubt I will be the first to pick the following nit. I assume that by “polyandrous males” she actually meant “polygynous males”. Or is there some really obscure joke that I’m missing?
More on moonbows
It seems to me that James Hamilton-Paterson may have overlooked some rather significant factors in making the comment, “I can’t see why the right conditions of strong incident light on falling rain should occur any less often by night than by day” (Letters, 29 April). Two major aspects come to mind:
There is a huge difference between the brightness of moonlight and sunlight. The Moon only intercepts a small fraction of the radiation from the Sun, of which only about 3 per cent is reflected from the lunar surface, and not much of that arrives on the Earth. According to the Larousse Encyclopedia of Astronomy, at best the Moon gives only 1/450 000 of the Sun’s light.
In humans, colour sensing depends on the cones on the retina while black-and-white vision uses the rods. The cones are far less sensitive which means that the light level needed for colour perception is considerably higher than for black-and-white vision.
In my experience, in these latitudes, a person who has good colour vision and whose eyes have become adapted to low-light levels needs an exceptionally clear and bright moon near the full to be just able to differentiate between the red colour of a brick wall and the green of grass and leaves 鈥� even though the same person can see sufficiently well at far lower light levels to move about in the monochrome outdoor world at night without much difficulty, and some can do so even by starlight.
In view of the need for good colour vision and exceptional moonlight, the scarcity of reports of coloured moonbows is hardly surprising.
Hamilton-Patterson comments that although he has never seen a reference to such rainbows they are doubtless well-documented somewhere.
One description which exactly matches his is to be found in the works of the Scottish poet Hugh MacDiarmid. In the poem “The Watergaw” MacDiarmid writes:
Ae weet forenicht i’ the yow-trummle
I saw yon antrin thing,
A watergaw wi’ its chitterin’ licht
Ayont the on-ding.
As any Lallans speaker can tell you, this describes a cold grey rainbow showing against a heavy rainstorm in the early evening. Nice to know poets can get there first.
Lunar rainbows were described by Aristotle in his Meteorologica. He describes their rarity as being due to the fact that they are only likely to be visible near the time of full Moon (when it is bright), and when the Moon is low in the sky (so that it may shine below any clouds on the other side of the sky): a total time of only a few hours a month.
Other unlikely conditions must coincide: there must be clear skies around the Moon and localised rain showers opposite (uncommon at night in temperate climates), and of course the observer must not be asleep. Aristotle describes having seen such a thing only twice in fifty years, a statement which led to a longstanding myth that lunar rainbows are only possible twice in fifty years.
This reference 鈥� and many more 鈥� may be found in The Rainbow 鈥� from Myth to Mathematics by Carl Boyer (Macmillan Education, 1987).
The spectrum of colours in a lunar rainbow is of course the same as that in a Sun rainbow, since moonlight is reflected sunlight with minimal modification. The reason why a lunar rainbow appears white (and also why a moonlit landscape has a mysterious silvery look) is that the light intensity is very low and our eyes will be dark adapted 鈥� their colour-sensitive cone receptors will be inoperative.
The spectral sensitivity is also shifted a little toward the blue, so a lunar rainbow will appear to have a slightly smaller radius than a Sun rainbow.
Stoned spiders
Your article on spiders under the influence of drugs states that the work was done by NASA in Alabama (This Week, 29 April).
P. N. Witt, C. F. Reed and D. B. Peakall wrote a text called The Spider’s Web (Springer Verlag, 1968) in which they reported this type of bioassay work extensively. It was built on Witt’s earlier German publication of 1956, which itself grew out of earlier work begun in 1948.
On the next page, Debora MacKenzie describes “the coelacanth’s limb-like pectoral fins making it the only known survivor from the era when vertebrates began to evolve into land-dwellers”. Setting aside the probability that the modern coelacanth is probably not a species that was present in the past, but a descendant from past species, MacKenzie neglects the four well-known species of lung fish from Queensland, Africa and South America. These fish all have lobed fins.
Yes, it seems that scientists have been turned on by the idea of spiders under the influence of drugs for some time. The NASA researchers have taken the idea a stepfurther by trying to create a more accurate toxicity test by adapting statistics from crystallography (applied to the “cells” of the webs) and devising a computer program to crunch the numbers 鈥� Ed
Breast is best
Is the rise of obesity, “that great bane of Western affluence”, and the decline in breast-feeding that took place with the introduction of formula milk just a coincidence (“For a few burgers more 鈥� “, 22 April)? Or could people lose the ability to judge their energy needs by being denied the opportunity to practice it in infanthood?
If infants are allowed to breast-feed as frequently and for as long as they want, they can have considerable influence on the intake of specific nutrients, especially fat. The concentration of constituents of breast milk changes during a feed. The “fore” milk is large in volume, but watery and low in fat. This gradually progresses to “hind” milk which is low in volume but rich in fat.
If breast-fed infants require increased amounts of fat, they obtain it in high concentrations by prolonged feeding from one breast. If they have received sufficient fat they come off the breast, although they may feed from the other breast if they require more water, carbohydrate or protein. It is an extremely clever system.
Bottle-fed infants receive all their nutrients as a homogeneous mix in a concentration and volume dictated by the milk manufacturers. A regimentally breast-fed baby (10 minutes each side every four hours) will also be denied much of the control of their water and fat intake.
Perhaps by interfering with early feeding behaviour there is a risk that the subsequent ability to match food intake with energy requirements will be compromised. Subsequently, this may fail to return even when control over food intake is restored.
Note, however, that the decline in breast-feeding levelled off around 1980, and in many countries has subsequently increased 鈥� Ed
Lopsided lure
David Concar’s article on body symmetry was a very interesting read (“Sex and the symmetrical body”, 22 April). However, it sparked a few questions in me. If symmetry is so important, why are so many hairstyles parted left or right? And why is the wearing of an earring on one side (deliberately upsetting the balance) considered so attractive in males? Could this be a modern conscious rejection of our biological preferences for symmetry?
The case for symmetry being a core element of beauty is even stronger than presented. “Average” faces, created digitally or photographically from many images, are often highly attractive. Composites of a selected set of attractive faces are even more attractive, and exaggerated versions of these are the most attractive, but slightly less symmetrical.
Further, radial symmetry will be constrained by functionality, whilst asymmetrical hairstyles or jewellery may aid individual recognition (or even work on the handicap principle, whereby those who are physically favoured affect “handicaps” to show how little they have to care about the matter).
Attractiveness may therefore include features unrelated to symmetry, but since many such preferences are consistent across cultures they are also likely to benefit the genes of a choosy partner.
Pay reviews
Phyllis Starkey argues that anonymous peer review is “the best we’ve got” (Forum, 22 April). One problem with the current review process is that it is highly labour intensive and can take a very long time because reviewers often have to find a slot late at night when their paid duties are completed.
The quality of reviews is also highly variable, ranging from an extensive considered study, much better than the paper reviewed, to a scribbled note amounting to, “don’t publish, it’s rubbish”.
Reviewers’ employers should be properly paid, at commercial rates. The reviewers would then be allocated time and resources to do the job professionally, and be prepared to stand up and defend their recommendations. Editors should be similarly paid.
Only publication in such professionally reviewed journals should count in research quality assessments. We now have the World Wide Web for rapid dissemination of “for information” publication, much of which really does not need reviewing. Even in referred journals, the reader cannot take anything as “true” without critically reviewing it themselves. For most researchers, WWW would be quicker and simple; you can always print the paper out to read on the train or plane.
Fishy facts
In your article on overfishing, it is stated that catches soared to 101.3 million tonnes in 1993 (This Week, 25 March). Unfortunately this statement gives a false impression that marine fisheries have improved in the last year.
In fact, the figure quoted represents the total world production of fish, crustaceans and molluscs from both capture fisheries and aquaculture. It also groups production from marine and inland waters.
A better set of figures for 1993 would be: total world production 101.4 million tonnes, of which the total from capture fisheries is 85.7 million tonnes (marine 78.8 million tonnes and inland 6.9 million tonnes) and total from aquaculture is 15.7 million tonnes (marine 5.4 million tonnes and inland 10.3 million tonnes).
While total world fish production increased by 2.6 million tonnes between 1992 and 1993, 1.87 million tonnes of this was derived from aquaculture and only 0.8 million tonnes from capture fisheries. This adds to the growing evidence that the world’s fisheries have now reached an apparent level of stabilisation of total catch which really represents a considerable degree of over-exploitation as most stocks are degraded in composition and size structure at this level of exploitation.
The shortfall in production is increasingly being met from culture systems whose contribution to world production has been growing steadily over the past decade.
Shady insurers?
I was appalled to read Mick Hamer’s article about the heavy rate of loss at sea of bulk carriers (“Clampdown on the rust buckets”, 29 April).
What I would like to know is what the attitude of maritime insurers is. After all, surely it would go a long way to solving the problem if all marine insurers, before granting cover, were to insist on the production of a report from a reputable marine surveyor and were to lay down as conditions of cover requirements about proper use and maintenance of vessels?
I can only suppose that there are some shady insurers about who are prepared to offer cover on a “no questions asked” cut-price basis, no doubt calculating that they can afford the odd loss, on the basis of additional premium income earned over the years. Or am I just being cynical?
Eugenic agenda?
With reference to Nick Hopwood’s comment in his review of The Facts of Life: The Creation of Sexual Knowledge in Britain, 1650-1950 (Review, 22 April), the reason that I did not bring out “the unpleasant connections between Stopes’s mystical celebration of middle-class marital sex, and her promotion of birth control to prevent the breeding of the ‘thriftless’ and the ‘racially negligent'” was that I am very far from persuaded that such a connection existed.
It has become an unexamined clich茅 that a malign eugenic agenda underlay the whole of Stopes’s work; a simplistic assumption which ignores the complex and often contradictory nature of Stopes’s opinions and activities.
This additionally ignores the pervasive currency of eugenic thought throughout the 1920s, much of it a good deal more hardline than Stopes, who thought that a significant part of the problem of the “C3 population”, could be obviated by giving over-burdened poor mothers the means of spacing pregnancies and limiting their families 鈥� see, for example, her much reprinted Letter to Working Mothers.
It is perhaps additionally of interest to mention that when eugenic concerns appear in the copious correspondence from the general public received by Stopes, they are not about fears of some group “out there” recklessly and thriftlessly breeding poor stock. They are very largely about the anxieties of individuals as to whether they ought to have children in the light of what they perceive as hereditary failings within their own families.
Very very large
Although Peter Stockhill argues tbat scientists may be willing to initiate space missions that will last beyond their life span (Letters, 1 April), the politicians and taxpayers who provide their budgets may not share their altruism.
However, an interstellar mission will not be undertaken for a long time. Meanwhile, increasing understanding of the genetic basis for ageing may extend the average life span by between 10 and 20 years. Translated into mission duration, this will mean a threefold increase of the volume of space within reach of exploration.
In regard to the “stop-gap” FOCAL mission, time may be a smaller problem than guiding a probe with the necessary precision to find the solar focus.
I suggest a simple remedy: when a new generation of probes is sent to the outer solar system (Pluto, Neptune, Pholus, and so on) let them carry radio telescope dishes that can cooperate as a single synthetic aperture antenna. As the aperture increases, the error when tracking an object decreases. A radio telescope 80 astronomical units across may not guarantee hitting the solar focus, but it would help a bit.
Mass and metabolism
Inside Science (18 March) states that the basal metabolic rate (BMR) of an animal is proportional to the three-quarter power of body mass, which agrees with the book I consulted, The Restless Kingdom: An Exploration of Animal Movement by John Cooke (Blandford, 1991).
However, Inside Science goes on to say that the formula means that for every quadrupling of mass there is a trebling of BMR. This statement is incorrect. If quadrupling of mass did indeed lead to a trebling of BMR, then there would be no need to include a power of mass in the formula.
In fact, according to the formula, quadrupling of mass leads to BMR being multiplied by a factor of 40.75 = 2.8284. This figure is only fortuitously close to 3. If mass doubles, BMR increases by a factor of 20.75 = 1.6818. If mass increases ten-fold, BMR increases by a factor of 100.75 = 5.6234. If mass increases 100-fold, BMR increases by a factor of 1000.75 = 31.623.
The formula matches quite well to the example BMR data comparing an adult human with a baby. However, I am unable to relate the formula (or even the incorrect version of it) to the BMR data comparing a mouse with a human.
The article also goes on to say, “Whatever the underlying factors which relate” BMR to body mass, as if these factors are not understood. However, in the book I consulted, it was possible to derive the formula by consideration of the fact that BMR is proportional to cross-sectional area, that is, the pull of a muscle, and hence its oxygen consumption (a measure of BMR) is related to its cross-sectional area, which is proportional to the threequarter power of body mass. In this way BMR is related to body mass.