Uncombined heat
Tony Fogarty suggests that to realise the efficiency gains of combined heat and power energy-generation, all new power stations should be CHP stations (28 April, p 20). This is one of those superficially attractive ideas that quickly sours when practicalities are taken into account.
Although CHP is justified where suitable heat generation is adjacent to the site requiring heat, in most cases this does not apply.
Is Fogarty suggesting that necessary electricity generation capacity should be sanctioned only if the developer can find a site adjacent to people or businesses who will agree to take all of the heat, not to mention having to get permission to dig up roads to put in heat pipelines?
The efficiency figures he gives are those typically achieved when the balance between electricity and heat load is optimised. This may be difficult unless the heat load is required by a nearby industrial process. And the recipients of the heat want to be sure the supply is reliable. Back-up heat sources must be available for times when the main CHP plant is down for maintenance or repair. This last requirement both increases the capital costs and reduces the overall efficiency.
Finding your level
Feedback mentions a sign in the maths and physics building at the University of Tasmania reading “You are on level 2. Level 3 is one floor up” (21 April). This information appears to be necessary 鈥� for students at least.
You would be surprised how many university students pester you with questions like “Where is level x?” when they are standing on level x+1 or x-1 with plenty of information to say where they currently are.
For the record
鈥� On the graph of atmospheric oxygen levels accompanying the article “Breath of Life” (28 April, p 40) the Permian extinction was marked as a minor extinction rather than major mass extinction.
鈥� We incorrectly said that Doug Cartlidge works for the Whale and Dolphin Conservation Society (28 April, p 34). He is executive director of the European Cetacean Organisation.
Falsifying warming
Roger James asks for a “theoretically conceivable or possible observation” that would convince us that “global warming is not caused by carbon dioxide emissions from human activity” (14 April, p 22).
Here’s a suggestion for the sceptics. How about we eliminate emissions based on human activity, or at least reduce them down to some reasonable level not too far from pre-industrial levels. If the temperature then continued to rise, we’d have our counter-example and the case would be proven.
This is theoretically possible. But of course the sceptics want this result proved before we carry out the experiment, or claim it is too hard to carry out. There’s the fallacy.
Schr枚dinger's treacle
Michael Pavitt asks what happens when a quantum event causes a viscous fluid to creep, or not. That is, if it is observed to have flowed, was it creeping all along (14 April, p 22)?
The answer is that the observation determines not only “what is” but also “what was”. It determines the unobserved past as well as the unobserved present 鈥� the cat’s continuous breathing and the treacle’s running. It may seem illogical, but that’s the quantum world for you.
Chill out!
From time to time you report connections between genes and obesity (21 April, p 16, for example). But surely the genome of the UK population can’t have changed that dramatically in the short period 鈥� 50 years 鈥� of the obesity boom. It would seem much more likely that there is some new dietary, environmental or lifestyle factor at work.
A possibility that occurs to me is that winters are less severe; we go outdoors in them less, anyway; and houses, cars and offices are much warmer than they were, as a result of central heating. As a consequence, if 鈥� as seems likely 鈥� we are predisposed (like squirrels) to increase food intake for the winter, and nowadays it doesn’t get burned off keeping us warm, it will be retained as fat.
Is there evidence for this? There must be statistics on average winter temperatures, outdoors and indoors, over the past 50 years. How many calories are needed for the maintenance of body temperature over this range? The results may show that we can simultaneously solve the obesity crisis and global warming by turning our thermostats down to zero.
Before everything
In his feature, “The universe before ours”, David Shiga suggests that one day we may be able to answer the question “why is there anything at all instead of nothing?” (28 April, p 28). This is more than optimistic: the question is a priori unanswerable.
By definition, there cannot have been anything before everything that is, and there cannot be anything outside it or after it. Calculating the probability of there being something rather than nothing at all is pointless, because this is beyond probability. There just is something rather than nothing, and there can be no deeper answer than that.
From Peter White
You mention the issue of whether time is infinite or whether it has a beginning and an end. These possibilities both assume that the structure of time is analogous to a straight line. There is another possibility, that time might have a structure analogous to a loop: everything happens only once, but time is not infinite and has no beginning or end.
One model of the universe with which this would be compatible is one in which the expansion phase after the big bang is followed by a contraction phase leading to a big crunch. The singularity at the big crunch would not be similar to the singularity at the big bang; it would be the same one.
Time has a loop structure, and the singularity is just another point on the loop. I don’t know whether this is compatible with any of the models discussed, but it is at least a logical possibility and a way out of the dilemma.
Cardiff, UK
From Andy Howe
The feature reminded me of an essay by Roger Penrose over 20 years ago. According to the “strong” anthropic principle, the universe is the way it is because it needs to be observed by some self-aware life form. Penrose applied this argument to humans, explaining that the universe did not have to develop this way just to create the likes of us.
Noting that an uninhabitable universe of black holes is far more likely than one suitable for us, Penrose said: “The cheapest way of making a roomful of people, or even a world full of people, is by random selection…a statistical fluctuation, if you like, in an otherwise high-entropy universe.” Expand Penrose’s “world full of people” right up to the observable universe, and what you get is perhaps what the “black hole sea” model discussed in the feature is actually describing.
Sheffield, UK
From Paul Robinson
Am I missing something here? Isn’t asking what happened before the big bang rather like asking what conditions are like 25,000 kilometres below the Earth’s surface?
London, UK
Warming swindle
Alan Thorpe, attacking my film The Great Global Warming Swindle, tells us not to “play games with the evidence” (17 March, p 24). Right ho. Let’s not.
He says: “There is no question that the more CO2 there is in the atmosphere, the warmer the planet becomes.” Perhaps Thorpe is too young to remember the post-war economic boom. To remind him, it was the biggest explosion of economic activity in the history of human civilisation up to that point; an unprecedented volume of CO2 was pumped into the atmosphere from lots of factories. What happened to the temperature? It went down. According to most temperature records, it went down from 1940 to about 1975.
Coincidental with the post-war cooling was a marked downturn in solar activity. Yet Thorpe boldly asserts, without any supporting evidence, that solar variations have an insignificant effect on the Earth’s climate. I refer interested readers to the work, published in 2005, by Jan Veizer and Willie Soon .
Then Thorpe admits, reluctantly, that in the ice core data, the temperature variation is followed, rather than preceded by changes in the level of CO2 in the atmosphere. So carbon dioxide is clearly not driving climate. Awkward. So what is driving it? Thorpe says it’s the sun (mighty powerful thing, the sun), but then he tries, feebly, to salvage his CO2 argument by suggesting that maybe the resulting changes in CO2 amplify the temperature changes still further.
Oh really? As it happens, there is no evidence at all that this is true. Very often in the ice cores CO2 rises like a rocket, while the temperature plummets. So who is playing games? Thorpe implies that I think there is a global warming conspiracy. I don’t. But I know that lots of scientists (like Thorpe), and journalists too, have staked their reputations on this theory being true. Many have built their careers on it. I sympathise with them.
The editor writes:
鈥� For full discussion of climate myths, turn to Climate myths and www.newscientist.com/climatemyths 鈥� and comment on Veizer’s paper is at
Accident on porpoise
Discussing how to protect underwater structures from terrorists, Chris Cantell claims Westminster International’s diver detection system is unlikely to harm marine mammals because it can correctly identify a target on 98 out of 100 occasions (28 April, p 34). This sounds great, but to a marine biologist with a knowledge of marine mammal distribution, this level of error is deeply disturbing.
While it may be rare for such a system to encounter a diver, it is likely to encounter marine mammals with a frequency many orders of magnitude higher. Marine mammals may pass through the same area many times a day, and many thousands of individuals may pass within range of one of these systems every year.
A 98 per cent success rate implies that 2 per cent of identifications are wrong. This could mean hundreds of marine mammals being accidentally classified as divers and thus exposed to high-intensity sounds that could injure or kill them.
This level of error is in no way safe for marine mammals. Such automated systems should not be implemented until the classification rate is several orders of magnitude better.
From Mark Simmonds, Whale and Dolphin Conservation Society
Thank you for drawing attention to the conflict between marine wildlife and new undersea defences. I want, however, to clarify the effects of underwater noise on wildlife.
Interruption of normal behaviour, displacement from key habitat areas and impacts on hearing are likely outcomes of exposure to loud noise. For example, there is an association between strandings of beaked whales 鈥� a family of deep-diving species 鈥� and the deployment of certain military sonars.
Many stranded whales are found to have gas embolisms in their tissues. The most likely explanation is that the unexpected noise forced them to surface faster than their physiological tolerances would allow, causing gases to come out of solution and leading to a “bends-like” syndrome.
Further information on underwater noise can be found in a recent report from the US Marine Mammal Commission () and in our own publication Oceans of Noise at .
Chippenham, Wiltshire, UK
Overweight baby galaxies may solve mass mystery
Weighing babies has long been used as an indicator of healthy development (28 April, p 6). The almost mandatory visit by mothers and infants to the infant welfare nurse or health visitor is part of the culture of having children. It is good to see solid evidence that the growth charts are flawed in favour of babies fed on formula milk, and that a revision is under way based on the weights of breastfed babies. This can only be of benefit to infants and mothers alike.
The baby health clinic visit has always provided useful opportunities for mothers to learn the difficult task of caring for a new baby. However, a decade ago in a research project in Brisbane, Australia, we found that weighing was beset by error 鈥� so much so that any changes in the recorded weight of an infant under 9 months of age at weekly clinic visits were most likely due to error (Journal of Advanced Nursing, vol 25, p 587).
A longer period between weighings was necessary to detect real weight change. For older infants, the visits had to be at least a month apart.
One must be careful, however, of throwing the baby out with the bath water. We recommended that visits to the baby health clinics be used as education and learning sessions for parents, without the emphasis on weight gain so encouraged by some infant welfare specialists.
From Nikki Stokes
Growth charts based on formula-fed babies may do more than just put breastfeeding mothers under pressure: they may discourage new mothers from seeking advice from their local maternal and child health (MCH) nurse at all. I stopped visiting my local nurse after she used the formula-based growth chart to exaggerate my 8-month-old son’s “growth slow-down” and suggested I was being a negligent mother by continuing to primarily breastfeed. I also know other mothers who stopped attending check-ups with their MCH nurse after similar experiences.
Being a new mother is challenging enough without being undermined by well-meaning MCH nurses using these inappropriate measures of normality, which only serve to damage the nurses’ credibility and put new mothers at risk of missing out on the valuable support that MCH nurses provide.
Boronia, Victoria, Australia
From Kerre Willsher
For about 20 years as a maternal and child health nurse I used these charts knowing they were flawed, out of date and indicative of artificially fed white, middle-class, American infants. Unfortunately, there were no other guidelines available. In an extreme case I was using them on Korean children living in Australia. I always told their parents that the charts were dated and that as long as the infant looked well there was no cause for concern.
I am distressed that as a conscientious health worker I may have inadvertently put children on the road to obesity. I will be relieved to see charts that are more accurate and in context, but will always correlate them with my own observations.
Whyalla, South Australia