Carbon-free nuclear?
Wade Allison produces a good argument for drastically raising the limits on the amount of radiation to which people can be safely exposed (31 July, p 24). I am less convinced by his use of the phrase “carbon-free nuclear power”.
Nuclear power is certainly dependable, but the construction and decommissioning of power stations and the mining of uranium require energy and generate carbon dioxide. Indeed, the extraction of uranium will gradually require more energy over the years, as the grade of the ore declines and deeper deposits have to be exploited, according to researchers in Australia at Monash University and the University of New South Wales ().
To put it in perspective, a 2008 study by Benjamin Sovacool at the National University of Singapore found that the average life-cycle carbon emissions of a nuclear power plant amount to 66 grams of carbon dioxide equivalent per kilowatt-hour of electricity produced, compared with 960 g for a coal-fired plant, 32 g for a solar photovoltaic facility and 10 g for an onshore wind farm ().
There is a case for nuclear power, but it is not as strong as its proponents often claim. As Jim Riccio, Greenpeace’s nuclear policy analyst, has stated: “There’s no such thing as a carbon-free lunch for any energy source.”
Cholesterol confusion
In your recent article on cholesterol (17 July, p 5), William Neal of West Virginia University is reported as suggesting that screening children for high cholesterol and treating those with elevated levels would reduce their risk of developing coronary heart disease later in life, thus preventing hundreds of premature deaths each year.
Yet in a letter in your 3 July edition (p 29), Marshall Deutsch refers to studies that show older people with high blood cholesterol live longer than those with low blood cholesterol.
Am I right to be confused? As a 78-year-old with a blood cholesterol level that was considered normal 20 years ago but is now deemed slightly too high, should I be sorry or glad that statins were not around when I was a child?
William Neal writes:
鈥� Mortality from heart disease is influenced by many more factors than blood cholesterol level. Family history is crucially important: we all know of 90-year-olds who smoke. But there is good evidence that high levels of bad cholesterol are associated with coronary artery disease.
A generation ago it was felt that a total cholesterol level of less than 240 milligrams per decilitre was acceptable, but large population studies now indicate that the risk of early heart disease is considerably lower when the total cholesterol is less than 200 mg/dl.
A very small percentage of children, those with familial hypercholesterolaemia or diabetes, require statins. But our findings continue to indicate that a healthy lifestyle is more important than any pill. The key to preventing most illnesses is physical activity and a nutritious diet.
A man's view
While analysing the reactions of the 19 men you asked to look at alternative covers for New 杏吧原创, did it occur to you that the cover they most strongly favoured bears a strong resemblance to a woman’s breast (7 August, p 32)? It even has the appearance of having a nipple. The other two designs look muddled in comparison.
This hardly seems a viable or even-handed test of brain activity and purchasing preferences, especially since you completely disregarded the possible reactions of women. There are female scientists, you know. And female New 杏吧原创 readers. Or, at least, there used to be.
The editor writes:
鈥� The decision to use male subjects was an entirely practical one. We had the time and resources to run tests on about 20 subjects; NeuroFocus advised us that to get meaningful results they should all be the same sex. Given our predominantly male readership, we decided to use men. We would very much like to run a similar experiment with women.
Pressure to confess
In his article about the doctor who doubts shaken baby syndrome (31 July, p 8), Andy Coghlan states: “No independent witness has ever seen a shaken baby with such symptoms, the only evidence has come from confessions.” It is important to add that confessions can be unreliable because there can be so many pressures on parents to confess, such as the threat that their other children will be taken into care, or the promise of a shorter sentence.
They may also be advised to confess to dropping the baby accidentally. In many cases they are told that shaking is the only way their baby could have received the injuries. Furthermore, the parents must deal with such pressures while suffering intense emotional distress at their child’s death.
A confession may look like an attractive option if it reduces the risk of parents having to fight their case in court, with pathologists and paediatricians testifying against them, and removal and adoption of their children and a prison sentence the likely outcome. Confessing to a crime they may not have committed could allow the other parent to keep the remaining children.
Let there be dark
Peter Aldhous reports that night-time lighting is having a disruptive effect on nocturnal animals, and suggests we dim the lights for their sake (17 July, p 8).
We might do so for our sake too. As a certified snake-catcher with a permit to relocate venomous snakes away from habitation, I frequently speak to people about how they can reduce the risk of encountering an undesired reptile.
One tactic is to use minimal outside lighting at night. Lights attract insects, insects attract frogs, toads, geckos, skinks and other animals, which in turn attract hungry snakes. For our own safety, let there be dark.
War in the air
Kate Ravilious’s article “Patterns of war” is correct to highlight the influence of Frederick Lanchester’s ideas on military thinking (31 July, p 34). However, it confuses a number of aspects regarding the Battle of Britain.
The “big wing” strategy involving large formations of aircraft was certainly not the favoured strategy in the earlier phase of the battle. The paper you cite () comes to no definitive conclusion over the strategy’s effectiveness, other than to observe that there is no evidence that a greater concentration of RAF numbers led to greater fighting strength. It does, however, note that Lanchester’s key insight- that loss rates are proportional to enemy numbers- was broadly correct for the RAF but less so for the Luftwaffe.
Fortunately, the RAF had prepared for the attrition that war would bring by planning for high rates of aircraft production and a comprehensive pilot-training programme, underpinned by an extensive logistic organisation with significant repair capability. As a result, the RAF got steadily stronger as the battle progressed- unlike the Luftwaffe, which became steadily weaker.
Spark of invention
Catherine Brahic notes in her article about the origins of cooking that the earliest confirmed archaeological evidence of fire at a site of human habitation goes back to 790,000 years ago (17 July, p 12). But people could well have been making fire in a domestic setting much earlier.
In this semi-rural area of New Zealand, there is a wandering, shallow stream whose shores and bed are covered with large rounded rocks and pebbles of all sizes. Some years ago, a small band of local children found that if you strike these rocks together they create sparks. After lots of time and many attempts, these children managed to ignite small campfires.
Since the earliest archaeological record of stone tools is around 2 million years ago, we imagine that this process of discovery and invention must have occurred many times. The question is, were ancient hominids as bright and inquisitive as modern human 10-year-olds?
Hidden cost of wind
In their defence of wind power, J茅r么me Guillet and John Evans state: “You end up paying less for your electricity when wind power is part of the mix” (24 July, p 24).
This is simply untrue. Industrial-scale wind power is so capitally expensive per megawatt-hour generated that it would not be commercially viable, in the UK at least, without the Renewables Obligation, which obliges electricity suppliers in the UK to source a proportion of their electricity from renewable sources. The CEO of the UK power and gas company E.ON UK is on record as saying: “Without the Renewable Obligation certificates nobody would be building wind farms” ().
The Renewables Obligation in effect delivers a subsidy that more than doubles the value of electricity from onshore wind farms, and in some cases more than trebles it offshore. It also compels the sale of renewably generated power, which because of its unpredictability, would not otherwise be marketable.
Flying for breath
When discussing the controversy over atmospheric oxygen levels during the age of the dinosaurs, Stephen Battersby asks: “Did the dinosaurs have to breathe heavily despite their efficient bird-like lungs?” (17 July, p 38).
A more interesting question is, what evolutionary imperatives resulted in the development of those efficient lungs, which were later important in the flight ability of birds? If oxygen was plentiful, as suggested by researcher Tim Lenton in the article, there would have been no need for highly efficient breathing systems. Robert Berner’s competing model of low oxygen levels seems far more likely, and might be supported by the steady increase in the size of flying dinosaurs before they became extinct: as the air became thinner, bigger wings would be needed for flight to be possible.
Gorilla in the midst
When viewing a video of people moving around and throwing a ball, many observers fail to notice a gorilla enter the scene (26 June, p 32). But is there a difference between watching an event in a two-dimensional video and experiencing it in real life? Did the experimenters compare people watching the video with those seeing the same scene live?