Crusty creation
Lawrence D’Oliveiro wonders whether continental crust is disappearing (17 November 2007, p 24). In fact, new continental crustal material is continually created by partial melting of rocks in the denser and silica-poor mantle and partial solidification of existing magmas. Both processes produce magmas richer in silica 鈥� the building blocks of continents. These rise and solidify, forming new crustal material. When teaching this to students, I likened it to the formation of scum when you boil fruit to make jam. The continents, I would tell them, are truly the scum of the Earth.
For the record
鈥� The “record-breaking crust” we mentioned in Greenland (22 December 2007, p 24) is 3.8 billion years old 鈥� not 1000 times younger, as we stated.
鈥� We described Weta Digital as “giving Gollum a voice that sounded human” (27 October 2007, p 32). Gollum’s words were spoken by the human actor Andy Serkis.
Time police
In response to the letter from Lee Cottrell (1 December, p 25) and concerning a popular time travel paradox: this is a highly speculative consideration given that neither do we possess the capability to travel in time to the past nor do we have anything approaching a useful model of the properties of time.
However, it has been suggested that every event precipitates a divergent future. Would it then, amongst the myriad branching of multiverses, be possible to acquire certitude that you had travelled back to your “own” past? The murder of what you believed to be “your” grandparents would affect possibly only one of the almost infinite possible versions of “you”, but highly improbably yourself.
What if, by chance, you were able to arrive in your own past? Might you then engender new branches in which, upon returning to your “original” time it would be discovered that you either possessed differing grandparents or now belonged to a future where your attempt had failed (the successful attempt being in the past of an alternative now)?
Clearly, if you ceased to exist then you would be unable to act, allowing your grandparents to conceive, allowing you to act thus ensuring that you ceased to exist, allowing your grandparents to conceive, allowing you to act thus ensuring that you ceased to exist, etc, etc ad infinitum.
Cat got the cream
Feedback reports research involving a “bottomless” bowl of soup (13 October). Readers may be interested to learn of a similar experiment that I carried out on the family cat, Trixie, in about 1952. I hasten to add that I was then in my early teens. There was not then 鈥� so far as I am aware 鈥� any need to obtain a licence for animal experiments and the cat was free to leave at any moment of her own choosing. Which she did.
I had wondered why it was that a saucer of milk appeared to be just the right measure for a cat. Had saucers been designed with cats in mind? Or perhaps vice versa? So one evening I waited until Trixie had finished her bedtime milk and then refilled the saucer. This she ignored, and indeed became very cross at being repeatedly taken back and encouraged to have a second helping.
Not content with these results, I set up a length of Bunsen tubing feeding the saucer from a glass filter funnel supported by a retort stand. The cat began to slow up when she had drunk the equivalent of two saucers of milk, but carried on valiantly until she was just past her third helping. She then left the house. Quickly.
With the benefit of hindsight it seems I should have published this experiment 鈥� I too might have won a prize!
Only financial bilge
It’s good to see a profile of Arthur C. Clarke (1 December, p 58), and particularly a reminder of the days when he, as an officer of the British Interplanetary Society (founded in Liverpool in 1933), was arguing the case for space travel against ignorance and lack of ambition.
Andrew Robinson repeats the old “utter bilge” quotation from Richard Woolley, the Astronomer Royal. Though this sounds as though Woolley was an old fuddy-duddy, Robinson crucially misses the point that he was arguing about the cost of space travel, and that he was right.
Woolley is actually reported in Time in 1956 as saying about space travel: “It’s utter bilge. I don’t think anybody will ever put up enough money to do such a thing… What good would it do us? If we spent the same amount of money on preparing first-class astronomical equipment we would learn much more about the universe.”
So what changed? Woolley’s estimate of a prodigious cost for a space programme was correct. It was the successful launch of Sputnik the next year, part of a Soviet campaign to outdo the west, which persuaded the Americans to fight the cold war by proxy as a space programme.This resulted in Kennedy’s decision to fund the Apollo programme.
Woolley was certainly wrong in the long term, but as Clarke points out in Greetings, Carbon-Based Bipeds (using a slightly different quotation) he was wrong for a very good reason and (at the time) more nearly right than the naive underestimates of the British Interplanetary Society.
It’s not by chance or pure idealism that the revival of the American space programme comes after the decision by China to go into space.
Panel panacea
The map showing the parts of the globe best suited to generating solar electricity and the area of solar photovoltaic panels required to meet our existing needs (8 December 2007, p 32) makes the prospects look very dim indeed. The area is the size of a small country!
At present, a large proportion of energy is wasted on transmission from centralised sources and through other inefficient practices. Much of the electricity we now generate is used to produce low-grade heat. There are much easier and more sustainable ways of producing this energy. If electricity were used rationally and efficiently, the area of photovoltaic panels required would be relatively small and our solar future a lot brighter.
More light than heat
The effect whereby an increase in central heating output is required to compensate for the heat lost when replacing inefficient bulbs or appliances with more efficient ones is known as the heat replacement effect. When calculating savings, this is accounted for by applying reduction factors, and that it may not be explicitly mentioned does not mean it is not considered.
The system boundary for the delivery of electricity extends well beyond the home to the power station chimneys. In the UK, electricity generation emits 2.5 times as much carbon as natural gas per unit of energy generated, and is four times as expensive. So for every kilowatt-hour of heat he receives from his light bulbs, Dave Riddlestone (8 December 2007, p 24) is causing 2.5 times as much carbon dioxide to be emitted as he would if that heat came from natural gas 鈥� and paying four times as much for the privilege.
Concerns about central heating systems wasting energy by heating unused rooms can be resolved by fitting a full set of heating system controls, especially thermostatic radiator valves, which allow the temperature in each room to be controlled separately.
Dave Riddlestone must have an exceptionally well-insulated home if his electric lighting provides adequate heating in winter. If it does, he must be wasting electricity when the weather is warmer.
Well done the European Union for mandating the phase-out of incandescent light bulbs.
Son ou lumi猫re
When Harry Collins asked people who are colour-blind and those without perfect pitch to pretend otherwise, it seems to me that the colour-blind were at an advantage (24 November 2007, p 58). When trying to convince judges, through questions and answers, that they are fully colour-perceiving, colour-blind people would be aided by the fact that they can already distinguish between some colours (unless Collins found extremely rare totally colour-blind subjects).
To fake it, they only need know how to talk about the colours they can’t identify (“red is bright and angry, it reminds me of fire”). Is this the “interactional knowledge” that Collins describes?
Trying to pass as pitch-perfect would be harder, as you either have it or you don’t.
Moth myths
In his otherwise excellent article, Jaap de Roode unwittingly perpetuates some more myths about the peppered moth (8 December 2007, p 46), and in particular about Bernard Kettlewell’s classic experiments in the 1950s.
Kettlewell placed moths on both branches and tree trunks where they would not be exposed to direct sunlight. The only moths placed during the daytime were for the direct observation experiments, to replace moths that had been eaten.
For the crucial mark-and-recapture experiments, moths were placed at dawn, while they could still move about.
In a control experiment, in which Kettlewell released moths before dawn when they could fly to their own resting places, the predation percentages were indistinguishable from those for hand-placed moths. There was even an internal control: some moths evaded capture on the first night after release, and were captured on the second night, after spending the day in spots of their own choosing. Again, the predation results were indistinguishable from those for the hand-placed moths.
It is not clear how the myth that Kettlewell placed moths only on trunks and only in daylight came about, as the details are set out clearly in the original papers. Perhaps, like the myth that Arthur Eddington fudged his eclipse results, a good iconoclastic story has a momentum beyond the reach of mere facts.
The story of the peppered moth is one of natural selection. A previously scarce but existing group (dark moths) became more common under favourable conditions (dark trees) than a previously favoured group (light moths that rested on light trees).
That natural selection is at work in the world is self-evident. The crucial and more interesting question is whether natural selection is responsible for the diversity of life, and indeed life’s very existence. The peppered moth may have generated much intellectual heat but has done little to illuminate this issue.
鈥� Yes, the peppered moth is an example of natural selection, but that is not to damn it with faint praise. Natural selection is a key element of the theory of evolution which creationists seek to destroy. No, the peppered moth is not an example of speciation 鈥� of the origin of diversity 鈥� but nobody ever said it was. And yes, it doesn’t shed any light on whether natural selection can explain the origin of life but, again, who claimed it did?
Approximate truths
In his article about establishing a causal link between human activity and harm to the environment, Andrew Baker claims that this can never be possible because “uncertainty rules” (24 November 2007, p 22). Yes, it can be claimed that Newton’s theory of gravity is “flawed”. However, considering the solar system, it is equally true that Einstein’s theory of gravity offers only minor corrections for all but a few solar-system bodies.
Nowhere in “real life” do we demand absolute proof. The fact that some witnesses lie does not mean that we banish all from court. Half of all marriages fail, but we do not forbid weddings.
So although Baker’s statement that there is no certainty might be correct from a philosophical point of view, for all practical purposes it is meaningless.
Baker also demands that scientists should emphasise the uncertainty of their results. 杏吧原创s do this all the time when they speak of evidence rather than proof.
Freud's legacy
In her article about the importance of unconscious thought, Kate Douglas writes: “Modern notions of the subconscious were invented by Sigmund Freud as part of his now discredited theory of psychoanalysis. These days the subconscious is on a firmer scientific footing 鈥� although many neurobiologists avoid the word ‘subconscious’, preferring ‘non-conscious’, ‘pre-conscious’ or ‘unconscious’ to describe thought processes that happen outside consciousness” (1 December 2007, p 42).
In fact, it was Freud who postulated the theory of a system of the unconscious, pre-conscious and conscious, and he was well aware of the power of the unconscious in influencing our choices and actions. It is often forgotten that Freud was no mean neuroscientist himself, author of more than 200 neuroscientific titles, which included substantial original work, including his research on aphasias.
Freud left a heritage of psychoanalytical psychotherapy that remains an important method of treatment in the UK’s National Health Service.
鈥� We appreciate that the theory of psychoanalysis has many supporters and has made an important contribution to modern psychiatry. However, Freud’s theory of psychoanalysis 鈥� the idea that the unconscious mind is split into id, ego and superego, which compete for control over our thoughts and actions 鈥� has long been discredited as a scientific theory of how the mind works.
Fish facts
It is dismaying to see the UN Food and Agriculture Organization promoting the idea that we need more fish farms to avoid overfishing wild stocks (1 December 2007, p 10). For salmon farming at least, this is agribusiness propaganda which covers up the truth touched upon at the end of the article: for each live-weight kilogram of farmed salmon produced, around 3 or 4 kilograms of wild fish are required to make their food.
Far from being a solution, salmon farming as practised now is part of the overfishing problem. Unless farmed fish can be produced without feeding them more than their weight in wild fish, aquaculture will continue to be a drain on wild stocks.
Energy incentives
There are many things a government can do to encourage the generation of solar electricity in addition to guaranteeing that it can be sold at a premium price (8 December 2007, p 3). These include: purchasing solar equipment in bulk at a good price, and passing the saving on to the private buyer or contractor; not charging sales or value added tax on solar equipment; allowing an immediate tax write-off of its full price; passing on carbon credits to owners of solar panels; and waiving road taxes on electric vehicles. Another is to implement the “Berkeley option”, in which municipal bonds finance the equipment, paid back through electricity bills over 20 years.
Debunking biofuel
You go some way towards debunking the fallacious reasoning used to justify biofuels as a way of reducing greenhouse gas emissions (15 December 2007, p 6 and p 3) 鈥� but there is more.
The net greenhouse gas saving for current biofuel crops in temperate regions is not more than a tonne of carbon per hectare per year 鈥� and is sometimes negative. But we need to take account of the opportunity cost of the land on which biofuel crops are grown. Reforestation, for example, could remove at least tens of tonnes of carbon per hectare from the atmosphere: so the payback period is decades at best. Even in the tropics, annual greenhouse gas savings are a few tonnes per hectare, at most.
Growing biofuels may require land to be cleared, perhaps indirectly: for example, because food production has been displaced by the biofuel crop. Land clearance results in immediate greenhouse gas emissions, whereas the biofuel savings occur over time.
Then there are the issues of displacement pointed out in the letter from Elliott Spiker (15 December 2007, p 18). Using biofuels may merely free up fossil fuels for someone else to use, perhaps in another country. National governments and the European Union should abandon all subsidies and quotas for biofuels forthwith.