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There will doubtless be many antagonistic responses to your interview with Laura Agustin, but I say "hoorah" for her views on prostitution (6 July, p 25) . Anyone can sell all sorts of body-based services, but only the sale of sex is considered to be wrong. This simply boils down to the idea that sex …

Caroline Williams discusses the possible use of smart meters to enable power companies to control customer appliances when demand exceeds supply, and the alternative self-sufficient "community" grids which use local storage (22 June, p 38) . Also worth considering is the use of dynamic tariffs based on the real-time price of wholesale electricity. With substantial …

In his look at computer programming, (8 June, p 36) Michael Brooks omits a branch of languages: the "English-like" ones of which LiveCode, by RunRev in the UK, is the foremost. Recently made open-source, anyone can access its coding, and its programs will run on any platform. It is easy to learn and memorise.

Stuart Clark's alternative moon-formation theory based on a massive natural explosion inside Earth was intriguing (6 July, p 30) . It made me wonder if a self-propelling planet could exist somewhere. It would need a less explosive but still significant heat output from a natural, internal nuclear reactor, and to be near enough to a …

Fred Pearce repeats the suggestion that "we are most likely heading for peak population by mid-century" (6 July, p 42) . This ignores the effect of evolution: when the environment changes, species change to maximise reproductive effectiveness. In the past it was only necessary to form a sexual partnership and children would probably arrive. Now, …

The complex biology of cancer's development from primary tumour to metastases was excellently described in your story (22 June, p 6) , highlighting exciting research to improve the outlook for future patients. It also opens the debate on the donation of tissue at very sensitive times for patients and their families. As an independent group …

Anti-terrorism vigilance as a result of misinterpretation extends beyond journalists with invoices for articles about chemical weapons in Syria (Feedback, 15 June) . I am an academic, but also a novelist under my pen name, Lior Samson. After my techno-thriller Web Games was published in 2010, for many months I could not fly from or …

I agree with Robert Gaines and Shanan Peters that if calcium and silica became more bio-available as unusually large amounts of rock were eroded, it could have prompted the Cambrian explosion in complex life forms (15 June, p 30) . Levels of calcium minerals would have been so high that organisms had to find ways …

We don't need the many-worlds interpretation of quantum theory (newscientist.com/article/dn9930) . Its prediction that a single universe splits into two when a quantum measurement is made is indistinguishable from a pair of universes that evolve identically up to that point, and then diverge. If the cosmos is truly infinite, that second explanation seems more natural. …

You discuss the need to create a new language of gestures to interact with computers (25 May, p 40) , but if movement-sensing cameras are now sensitive to 1 millimetre, would it not be easiest to use lip-reading?

The Feedback article on the zero per cent power-setting on a microwave oven chimed with me (18 May) . My manual specifically refers to this as a way of using the oven as a kitchen timer.

Letter writer Stephen Rowe is right to be confused about the use of the phrase dark energy (15 June, p 33) . It is not a very good name to explain the observation that the expansion of the universe is accelerating. On the other hand, "anomalous acceleration" just doesn't have the same ring to it.

The views of Lady Randolph Churchill are quoted in The Last Word on the subject of nations that boast most Nobel prizewinners (29 June) : "We owe something to extravagance, for thrift and adventure seldom go hand in hand." How does this compare with "necessity is the mother of invention"?

It is silly of (some) physicists to claim "there is no time" (15 June, p 34) . Physicists, like the rest of us, experience life sequentially: they are born, grow up, die, read this line before the next. If mathematical physics does not recognise sequence, well, so much the worse for mathematical physics. As for …

• We veered slightly off course in our look at citizen cartography (6 July, p 20) . Kenya's Map Kibera was a project of the GroundTruth Initiative, not the Humanitarian OSM Team.