Getting the wind up
John Etherington’s criticism of the financial support provided to wind power is fundamentally flawed because it ignores the high “external costs” of electricity generation by fossil fuels and also the subsidies that these fuels receive (21 August, p 27).
The European Commission published a report in 2003 that concluded the costs of the harm caused to human health and the environment by generating electricity from fossil fuels were significant (). In the UK, including these costs in electricity bills would have raised them by between 4 and 7 Euro cents per kilowatt-hour for generation from coal. By comparison, the external cost of generation from wind was estimated to be 0.15 Euro cents per kWh.
The energy market is further skewed by the subsidy of $557 billion that the was handed out by governments to the fossil fuel industry in 2008. A global subsidy of just $46 billion was given to renewable energy in 2009, .
The IEA research also concludes that the phasing out of fossil fuel subsidies, as agreed by the G20 last year, would cut greenhouse gas emissions by 6.9 per cent by 2020, equivalent to 2.4 gigatonnes of carbon dioxide. This is equivalent to the current emissions of France, Germany, Italy, Spain and the UK combined. This has to be the way forward in our climate-changing world.
Friends of the Earth Cymru
John Etherington suggests that the UK’s Renewables Obligation legislation 鈥� which compels power companies to provide a proportion of their power from renewables 鈥� is in effect a subsidy for otherwise unviable renewable energy sources.
He appears to have forgotten the indirect subsidies received by fossil fuel-based power generators, in that they have not had to bear any of the costs imposed on the rest of the world by their carbon dioxide emissions. If the true cost of dealing with climate change and other forms of environmental degradation caused by fossil fuel electricity was applied to these generators, their electricity would likely be thought unmarketable. All this without even considering the many direct subsidies received by coal, oil and other fossil energy industries.
Shaken babies?
Your editorial on the science behind shaken baby syndrome calls for new avenues of thought on the issue (31 July, p 3). After years of clinical paediatric practice and research into pressure relationships in the nervous system, I now consider that repetitive squeezing to calm a child might lead to similar symptoms to those of SBS.
The skull and spinal cavity are a closed box, with a shock-absorbing system to cope with sudden changes in pressure. This system consists of the cerebrospinal fluid bathing the brain and cord, and the venous “sponges” around the spinal cord, which hold blood that drains into the main veins returning to the heart. With each heartbeat or other change in pressure in the brain, an instantaneous transmission of hydraulic pressure causes these venous sponges to transmit an equivalent volume of fluid out of the system and into the azygos vein system of the upper abdomen and chest.
If the venous sponges of the spinal cord or the return of blood to the great veins is compromised, the shock-absorbing effect is diminished. One way that this can happen is by increased pressure in the chest, which restricts blood flow from the azygos vein system into the great veins, producing large rises in intracranial pressure. This inadvertent raising of pressure in the chest during physiotherapy on premature infants was probably responsible for bleeding into the brain 鈥� something which vanished when the chest pressure technique was stopped. I suggest that similar repeated episodes of apparently non-violent squeezing the chest may be the underlying mechanism in “non-accidental brain injury”.
Squeezing a baby around the chest, which might start as a calming activity, will raise intracranial pressure. If repeated it may cause quietness 鈥� unconsciousness 鈥� just by the fact of raising the pressure. At the ages where blood vessels are proliferating and easily damaged, raised pressure may cause blood leakage and even vessel rupture anywhere in the brain or spinal cord. I find it far more likely that the almost unconscious action of squeezing a baby around the chest to calm it, rather than shaking, may lead to a sequence of increased squeezing that could lead to death.
Waney Squier of the Department of Neuropathology, John Radcliffe Hospital, Oxford, UK replies:
The function of the system of intracranial vascular “sponges” and extensive dural venous reservoirs is unknown, but a role in buffering hydraulic pressure seems reasonable. These structures are much larger in newborns and in the first year of life than in the adult, suggesting they have a role during delivery.
The venous outflow from the brain returns to the heart via valveless channels; increased intrathoracic pressure and chest compressions during resuscitation increase pressure in the dural sinuses and may cause intradural bleeding, which is common in the young infant and readily mistaken for the thin film subdural bleeding often associated with non-accidental injury. Such physiological mechanisms should be considered. While childbirth and potentially CPR may cause intradural bleeding, whether the “unconscious action of squeezing a baby… to calm it” might do so is an interesting, but unproven, hypothesis.
Acoustic intent
Trevor Cox’s article on acoustic archaeology mentioned the debate about the intentional use of sound in prehistory (21 August, p 45).
Archaeo-acoustics is a broad subject, and there is no doubt about intentionality in the case of lithophones 鈥� rocks that ring when struck, creating drum or bell-like sounds. Indeed, Palaeolithic and Neolithic lithophones have been found bearing rock art or percussion marks. Under the auspices of the Royal College of Art in London we have been conducting acoustic mapping on Carn Menyn in Wales, the source of the Stonehenge bluestones. A ringing rock there is marked with artificial hollows 鈥� anyone making the markings would have heard the stone ring out.
Intentional use of the acoustical characteristics of stone chambers in Neolithic mounds is indeed harder to prove, but they would have been evident to anyone at any time who had ears. There is also some evidence of deliberate engineering. Archaeo-acoustic research helps us to acquire additional information from some archaeological sites and, in my view, the approach will become increasingly important and sophisticated.
Peter Sheppard Skaerved
I read Trevor Cox’s excellent article about the acoustics of ancient architecture on the way home from recording some new music, on a 17th-century violin, in a small 13th-century church. My sound engineer and I find that working in acoustic detail inside old buildings actually raises the awareness of the natural world outside their walls: the sounds of leaves, sonic qualities of different weather and even, on one occasion, a butterfly’s wings on medieval glass.
Rather than modern people being acoustically primitive, as Cox’s article suggests, my experience of listeners’ reactions to music and silence in different environments shows me that we are profoundly affected by subtle changes in our acoustic space. It is just that, with the constant aural clutter in the media, people get treated as if their aural sensitivity is crude.
London, UK
Pioneering unity
Reporting on Petr Horava’s ideas on how to unify quantum theory and relativity (7 August, p 28), Anil Ananthaswamy comments that the theory will be difficult to test because the “predictions will deviate from those of Einstein’s relativity only at energies far, far higher than can be probed in labs today”.
Rather than high energies, could we instead look to tests carried out over longer time periods and distances? The Pioneer 10 and 11 spacecraft, currently heading into the outer solar system, are experiments which have been running for nearly 30 years. Their acceleration towards the sun is greater than is predicted by general relativity 鈥� a phenomenon known as the Pioneer anomaly. Other satellites have experienced similar effects, but not planets.
Might this scenario provide a useful test bed to judge Horava’s theory against Einstein’s?
From Simon Williams
I read about the end of space-time with great interest, thinking that Horava must be about to replace Einstein, and everyone else would be using his work to good effect, until almost the end of the article and the mention of dark energy. Here it transpired that Horava’s theory “contains a parameter that can be fine-tuned” to allow the value for vacuum energy to fit observations.
This parameter sounds remarkably like what I, as a business analyst, would call a fiddle factor…
Cramlington, Northumberland, UK
Space recycling
Your article debates how to recycle a space station (21 August, p 5). I should think the enormous cost of constructing the space station would dictate that the facility be “mothballed” in orbit as a resource after its useful life. Its components could be used for future missions, a moon colony, or sold to a private operator for space tourism. Is it feasible to lift the facility to an orbit such as the Lagrange point L5 that doesn’t decay because it has the same orbital period as the Earth?
Probably guilty
The worst mistake in the thinking behind the use of DNA evidence in court is a simple one of mathematics (21 August, p 8).
Say that a court is told that there is a 1 in a million chance that the DNA matches someone apart from the suspect. If we assume that gender can be identified with absolute certainty, this means that for a case in the UK, there are 30 other people in the country who would match the DNA profile. So it is not a 1 in a million chance the police got the wrong person, it’s 1 in 31 that they got the right one 鈥� based on DNA evidence alone.
This is why it is important to have other evidence too, such as an eye witness.