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Your article reporting on the poor state of maintenance of wells in Ghana and Mali gives the erroneous impression that these problems are typical of other areas in Africa (28 March, p 4) . WellWishers, a group dedicated to funding wells in Ethiopia, has constructed 141 wells in that country over its seven-year lifetime. Apart …

Robert Adler reports that ancient footprints discovered near Ileret in northern Kenya could provide information on important questions about human evolution (7 March, p 10) . My first reaction was to question how the findings passed muster to be published in the first place as a report in Science , and secondly how Â鶹´«Ã½ …

Andrew Simms is right to highlight the inadequacies of the carbon trading system, which seems to be yet another way for the financial sector to try to make large sums of money, rather than a serious attempt to stave off global catastrophe (18 April, p 22) . There are more effective alternatives. For example, any …

Phil McKennna's suggestion that gasifying trash could solve the energy crisis was simplistic (25 April, p 33) . The materials that we now simply discard represent a problem and an opportunity at the same time. While recovering energy efficiently is probably an improvement on sending it to landfill, it would be even better to recover …

Tony Waldron's comments on research into treatments for myalgic encephalomyelitis (ME) fail to address the effect on these studies of confusion over the definition of ME (25 April, p 24) . In most studies into the efficacy of cognitive behavioural therapy (CBT) and graded exercise therapy (GET), the people who report in favour of the …

There seems to me to be a fundamental flaw in Saibal Mitra's idea for saving the world by applying an interpretation of the "many worlds" idea, reported in your recent news story (18 April, p 11) . The mistake is to try to apply the concepts of probability theory to an infinite set – in …

I suspect that James Dyson's space-saving kitchen gadgets you describe (2 May, p 20) will fail to be popular, for several reasons. For instance, very few people will ever want to replace all their equipment at the same time, and when a new appliance is needed, supermarkets sell kitchen gadgets at ludicrously low prices. More …

Sebastian Hayes argues that science is relative, but religious attitude is universal (18 April, p 24) , but he is wrong. A sufficiently intelligent being on the other side of the galaxy would conclude that gravitational attraction between two bodies is inversely proportional to the square of the distance between them. This conclusion follows from …

• Hal Pashler, whose criticisms of interpretations of brain scans we reported (2 May, p 4) , is at the University of California, San Diego. • We got the time it takes light to arrive from the Horsehead nebula wrong by a factor of a million: the light we see from it is a mere …