Letters archive

Theunis Piersma's article regarding the health issues of weightless space flight, while certainly correct about the biology (13 November, p 30) was incredibly pessimistic. Artificial gravity should solve all the physiological issues mentioned. While the exact level of artificial gravity required to maintain health is unknown, Earth's gravity would likely be the upper limit. Constant …

I was disappointed that Douglas Fox's otherwise enjoyable article on anthropomorphism left unexamined the empathy felt by people in hunter-gatherer societies for the animals they hunt (27 November, p 32) . In David Attenborough's series The Life of Mammals , one episode focused on Kalahari bushmen and "persistence hunting". This examined a hunter's techniques and …

When explaining the effect of biology and geography on the supremacy of western science, Ian Morris writes: "People in Australia, Siberia or sub-Saharan Africa stuck with hunting and gathering" (30 October, p 32) . With respect to sub-Saharan Africa, this is plainly wrong. In his book The Civilizations of Africa: A history to 1800 , …

I read Colin Barras's article on literacy in robots with interest as well as some amusement, given the quirks and vagaries of the English language (27 November, p 22) . It is easy to envision a robot-owner presenting his digital charge with a task list consisting of: dust the floors; prepare two rabbits for tonight's …

Reading about the mechanisms by which animals use magnetism for navigation (27 November, p 42) prompted me to wonder how they cope when the Earth's magnetic poles reverse, which happens on average every 300,000 years. Not only would the poles reverse, but the field strength would weaken during the time of change, perhaps being close …

Mark Schrope's interesting article on electric aeroplanes (6 November, p 40) did not mention the possibility of using cables or catapults to launch or assist planes into the sky. To an outsider, it seems that such a technique could reduce kerosene usage because the fuel used would not have to be lifted into the sky.

Why is the grandfather paradox so named (20 November, p 34) ? Surely the same effect would be achieved and the same paradox would result if you travelled back in time and killed one of your parents before they met. Why not call it the father paradox or the mother paradox? Yours, a nervous grandfather.

• We misspelled the name of Eberhart Zrenner in our article on retinal implants (6 November, p 10) . • In our diagram showing the human and Neanderthal evolutionary tree, the label for present-day humans should have read " H. sapiens with up to 4% Neanderthal genes" (4 December, p 32) .