Empty Australia
Obviously Tim Flannery sees the optimum Australia as a desert (22 June, p 42). His desired population number of between 7 and 8 million puts the population density at one person per square kilometre, exactly equivalent to the Western Sahara, which has the lowest density in the world.
Self-supporting China, at 133 people per square kilometre, may be too cramped for most tastes (although nothing compared to Singapore at 6942 per square kilometre), but Australia can support many more people than at present, based on other countries’ statistics.
Could Flannery be a voice in the wilderness?
For the record
鈥� In our news story on SETI (20 July, p 22) we mentioned the Rio scale, which is designed to inform the public how likely it is that an unexplained radio signal is from an extraterrestrial civilisation. We incorrectly stated that the scale runs from 0 to 1. It actually runs from 0 to 10.
Eco-construction
Your reporter Fred Pearce has slipped from his normal standards of excellence (13 July, p 38). The magnesium-based cements that he describes are not a green panacea.
Pearce quotes John Harrison, a technologist from Hobart, Tasmania, who proposes an industry that takes magnesium carbonate ore and converts it into magnesium oxide cement. Buildings using the MgO cement would absorb carbon dioxide from the air, turning cities into CO2 sinks. But the cement can only reabsorb at most the same amount of CO2 after the structure has been built as was released during the manufacturing process. You can’t use it to make a city a real carbon sink. The fact that magnesium cements are expensive should be a warning flag. It may just be due to a lack of economies of scale, but it’s equally likely to be due to the nature of the whole industry, from ore extraction, refining, cement manufacture and transport at all stages. These activities cost money and also cause CO2 emissions. It is important that a full life-cycle environmental analysis be carried out before governments and environment agencies start actively encouraging a magnesium cement industry.
It could well be that MgO cement is significantly less of a climate hazard than traditional calcium-based cement. However, wood or locally produced materials of any kind could well be better, particularly for housing. Making cities eco-friendly is a challenging but achievable goal. Tangible steps forward would include filling them with as many and as diverse trees and other plants as possible, and, as Barcelona has done, insisting that all new buildings have solar panels on their roofs.
Informed consent?
Sylvia Pag谩n Westphal’s article on IVF and the number of embryos implanted per cycle was right on the money (13 July, p 4).
The devastating consequences of preterm multiple births are well documented. As a neonatologist who looks after the babies that often result from the implantation of too many embryos (that is, more than one!), I can attest to the overwhelming morbidity and mortality that results. I wonder how many couples are told of the potential adverse consequences of multiple pregnancies before they give their “informed” consent to go ahead.
The news is good
I won’t be here to see it, of course, but I think that the advantages of a population of “only” 3.2 billion by 2150 鈥� which is still double the population at the start of the 20th century 鈥� will outweigh the disadvantages of labour shortage and an ageing population (20 July, p 38).
Life is cheap in many parts of today’s world, with millions living and dying in poverty and squalor. Things will only get worse if a growing population puts ever more pressure on finite resources and living space.
So a shrinking population is good news, not only for the human race, but also for the planet and the other species we share it with.
Letter
You ignore many advantages of a smaller population. Humanity will have a smaller ecological footprint, with less appropriation of land and resources.
True, there will be social problems, but each of our descendants will have a larger “slice of the cake”, and be more valuable to the wider community. The infrastructure of modern civilisation will be less strained than it is by the current seething masses, and we can focus more on solutions tailored to individuals. Quality of life can improve, for although 10 billion people cannot possibly achieve the standard of living of the present-day US, perhaps 5 billion can.
Do we want 50 great-grandchildren eking out a meagre existence in a world teeming with children, or five great-grandchildren enjoying a fair share of the Earth’s resources? We should stop viewing the current population figures as the norm, and instead look at them as a brief crest in the wave of human history. Quality, not quantity, should be the watchword of humanity.
Letter
Projecting a future fall in world population on current trends has one major flaw. Certain countries, especially in the Muslim Middle East, are far less affected. Strong patriarchal traditions, such as those confining women to the home, are a part of this.
The falling populations of the developed world will gradually be replaced by more fertile peoples, leading to renewed population growth in what could be an increasingly Islamic world.
All in a spin
Of course the Universe is spinning! Every free-floating particle or celestial body or galaxy is rotating, and I hope no one these days would ask the question asked by Ernst Mach in 1893, “relative to what?” (13 July, p 17).
An accelerometer attached to a spinning flywheel would show an acceleration 鈥� the spring pulling inwards to stop the weight flying off tangentially. The flywheel could be in deep space with no visible reference point.
Letter
Of course Mach was right. Nothing spins or does not spin, moves or does not move, without a frame of reference first being specified. It moves relative to that frame and that frame is chosen by the observer.
If the Universe is rotating there needs to be a centre of rotation (or does every point become a centre of rotation?). If so, the most distant galaxies would have phenomenal velocities, and yet they cannot exceed the velocity of light.
According to Einstein, the laws of physics change in accelerated frames of reference. A rotating body is an accelerated body (centripetal acceleration).
You report that a team at the University of Ulm in Germany proposes adapting the ring-laser gyros currently used to track rotation in aircraft and satellites to find out whether the Universe is spinning. What they will be measuring is not “rotation”, but a possible directional asymmetry in the laws of physics.
Letter
Space itself spinning? Truly revolutionary! If it is, then surely it must have a centre. Furthermore, the Universe would then have a plane of rotation, and so not look the same in all directions 鈥� another U-turn for my confused brain to try to absorb. Phew, gotta go鈥y head is in a spin!
Eugenie Samuel writes: There are solutions to Einstein’s equations of general relativity in which the Universe rotates. In these models, there is no centre of rotation. Instead, particles at every point appear to experience an accelerating force. This does indeed mean that the Universe would not look the same in all directions and detailed observations of this could be another way of detecting the spin.
Sniffing for oil
Your report on oil exploration using “microlepton” detectors looks very much like a remake of the “avions renifleurs” (“sniffer planes”) affair (6 July, p 7).
In essence, the affair goes back to 1976. Two “inventors” persuaded the management of the oil company Elf that they had developed a device capable of detecting oil fields using something like “targeted neutrons”. A site was even “detected”, but drillings produced no oil. The hoax was discovered in 1979, but made public only in 1985 after an audit. The cost of the whole affair amounted to almost one billion francs, and the resulting scandal was widely quoted in the French media around 1985.
What is interesting is the number of parallels with the British case: authorities not listening to specialists in the field (a junior Elf technical employee was even fired after expressing misgivings); the use of mysterious elementary particles 鈥� non-existent “microleptons” and the “memory” of neutrons; the use of aircraft to sniff out oil fields; and the drilling permits granted by the authorities.
Coral creation
I suggest that the phenomenon reported in your article on growing coral using electricity is by no means novel (6 July, p 38). The process of supplying direct current to a steel structure, by immersing the structure and an inert anode in an electrolyte, is a well-known corrosion control method called cathodic protection. It was first investigated by Humphrey Davy 鈥� also in sea water 鈥� and described by him in a paper to the Royal Society in 1824.
Interestingly he also reported the growth of a precipitated film on the protected metal, in his case copper. Davy writes: “I had anticipated the deposition of alkaline substances in certain cases upon the negativelyelectrical copper. This has actually happened. Some sheets of copper that have been exposed nearly four months to the action of sea water鈥ave become coated with a white matter, which on analysis, has proved to be principally carbonated lime, and carbonate and hydrate of magnesia.”
Nose jobs
You report that Australian researchers have started testing a treatment in which nerve cells from the nose are injected into the spines of people suffering from paralysis (13 July, p 18).
For more than a year a team from the Egas Moniz Hospital in Lisbon has been treating spinal cord injury patients with grafts from the olfactory mucosa.
Big genomes
In comparing the genome size of organisms, surely it is important to consider the entire life cycle of the organism, not just its immune system or “intelligence”(13 July, p 19).
As a biologist I see the fact that plant genomes are bigger than those of animals as entirely logical in terms of the organism’s total biochemical capacity and control. In essence, an animal can do three things that a plant cannot do: move, eat and think. Conversely, plants have the genetic and biochemical capacity and control for many processes not found in animals.
Here are some of the most obvious examples: regeneration of roots, shoots, leaves or flowering parts; photosynthesis; transpiration and water uptake through roots; surviving on basic mineral inputs; complex biosynthesis (amino acids, sugars, carbohydrates, lignin, vitamins, pigments, gums, latex and so on); distant fertilisation; survival as dormant seed. This suggests a large genome.
Dig deep
Deputy Prime Minister John Prescott calls for radical thinking about housing in Britain, especially in the Southeast.
Green belt land is to be progressively sacrificed. At what point will consideration be given to the possibility that far more people can live in central London 鈥� beneath existing housing?
The question is, why are no feasibility studies being undertaken on the proportion of people such as students and nurses who would be prepared to live underground, if commutes could be reduced to a few minutes? Who owns the huge volumes of space open to such development under central London? What are the costs of converting tunnel-drilling machines to work vertically? What are the construction, maintenance (air conditioning, lifts, and so on), and possible rental costs? What are the security risks?