Â鶹´«Ã½

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 – the building blocks of continents. These rise …

• The "record-breaking crust" we mentioned in Greenland (22 December 2007, p 24) is 3.8 billion years old – not 1000 times younger, as we stated. • 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.

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, …

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 – so far as I …

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 …

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 …

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 …

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 …

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 …

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 …

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 – although many neurobiologists avoid the word 'subconscious', preferring 'non-conscious', 'pre-conscious' or 'unconscious' to …

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 …

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 …

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 ) – but there is more. The net greenhouse gas saving for current biofuel crops in temperate regions is not more than a tonne of …