Letters archive

Richard Elwes reports on Harvey Friedman's fascinating work on incompleteness in Boolean relation theory, but it is quite a stretch to extend his work to ask "are the rules of arithmetic... unsound?" (14 August, p 34) . In logic, as in everyday language, the label "unsound" is generally reserved for arguments which prove false statements …

Your article on the role of fever in fighting infection (31 July, p 42) missed one of the most interesting chapters in this saga: in the late 1800s and early 1900s a doctor called William Coley attempted to cure cancer with fever, with some success. An earlier article in New Scientist (2 November 2002, p …

Robert Richardson warns us of the perils of squandering our limited helium resources (14 August, p 29) . Schemes to make a lot of money by cornering the market in a supposedly irreplaceable commodity usually fail, because the market is ingenious at finding either new supplies or alternatives. However, Richardson suggests that the chance of …

Matt Kaplan writes about the effect that meteors could have on the Earth's geology, suggesting that the Deccan Traps were caused by an impact somewhere else on the planet (5 June, p 38) . As a miner, I learned that rock is very strong under compression. All rock-breaking explosions had to be directed towards a …

Trevor Cox's discussion of the acoustics of ancient theatres reminded me of a trip to Greece with my medical student colleagues (21 August, p 44) . We tested the acoustics of the amphitheatre at Delphi by going to the top tier of seats and sending one of our number down to the stage. Not having …

Thomas Frost criticised using as a criterion for species membership the ability to interbreed to produce fertile offspring (31 July, p 27) . I was surprised that he did not cite the most widely accepted definition of species: the biological species concept. It was first proposed by Ernst Mayr, in his 1942 book Systematics and …

In his article on morphing dinosaurs, Graham Lawton discusses possible functions of the triceratops's neck frill, such as it being a signal of maturity. However, he surely implies its real function with the description: "it had numerous large blood vessels running over the surface" (31 July, p 6) . This suggests heat exchange: the frill …

Sebastian Hayes suggests in his letter that the laws of physics might evolve over time (26 June, p 30) . Some versions of this idea have already been considered in fact, such as the possibility that the gravitational constant changes over time. Even if we don't count that, we need to consider what would control …

The simile comparing gravity to an elephant, unaware of quantum fluctuations, or "microbes", on its skin (15 May, p 9) appeared in the same issue as Feedback's illumination of the meaning of numbers via elephant-related metaphors. The amount of amusement arising from this concordance was equivalent to .

• The correct reference for the paper by Rouzbeh Allahverdi and others on universal inflation (21 August, p 6) , is Physical Review D , DOI: 10.1103/PhysRevD.82.035012 . • Corsin Müller is at the University of Vienna in Austria, not the University of Zurich as we stated (21 August, p 12).