Letters archive

John Bailey's pessimistic view that a lack of alien visitors indicates there are no aliens out there (21 February, p 54) carries with it two hidden assumptions: an advanced civilisation will aspire to interstellar travel, and they will develop the means to do so. It may be that interstellar travel cannot be achieved on timescales …

John Bailey concludes that since we haven't been bombarded with self-replicating alien space probes or spotted heat signatures in space, there probably aren't any advanced civilisations living in our galaxy. He seems to think that advanced races will have a "more is better" philosophy, but climate change is showing us that the opposite is the …

We ought not to fear attracting advanced aliens through interstellar signals (21 February, p 8) . Considering the chances of any sentient life having the technology to detect, recognise and understand our signals, and the distances involved to travel to its source, we will be a very advanced race ourselves by the time they arrive. …

Jessica Hamzelou describes the enormous influence intestinal bacteria have on the behaviour of the human body (14 February, p 8) . I wonder if this casts doubt on the validity of epidemiological studies on the diet. Could the benefit of a Mediterranean diet be dependent on a Mediterranean faecal biota? To my knowledge, standardisation of …

I agree with Michael Le Page's argument for genetic alteration of embryos to treat those with major abnormalities (14 February, p 26) , but where do you draw the line? Congenital deafness? A genetic predisposition to cancer? A predisposition to stammering? I stammer, and am pleased I was not interfered with at conception. I think …

Hal Hodson draws our attention to the increasing prevalence of automated systems that tend to be driven by predictive equations (7 February, p 30) . These equations often have one thing in common: they rely on incomplete and proxy information to make their predictions. It is sobering to consider how accurate similar predictive equations are …

In examining whether the UK should press ahead with fracking for gas, you write that a lot of imported gas originates in Russia (14 February, p 10) . But according to government figures, the gas we import comes primarily from Norway, Qatar and the Netherlands. The prevalent misconception that we need to frack to keep …

You are correct. We meant to say that importing more gas to the UK could increase demand for Russian gas in other countries.

Colin Barras credits the leaf shape of the coco de mer tree for the high level of nitrogen and phosphorus in the soil around the tree, as it funnels rainwater and the nutrients it picks up down the trunk, but there is another explanation (14 February, p 13) . The dense, fibrous root zone of …

This is a very good point, and the researchers are looking into options to study the potential relationship between coco de mer and mycorrhizal fungi.

I don't think it is disputed that there was some biological contribution to the formation of the gold deposit in the Witwatersrand basin (7 February, p 11) . Since its discovery, various theories have been put forward as to how the deposit formed, including sedimentation, hydrothermal processes and precipitation by microbes. That gold can form …

Peter Borrows asks if roller coasters could be used to treat brain cancer (14 February, p 55) . The answer is no. The brain produces cerebrospinal fluid. Most of this fluid passes out to bathe the outer surface of the brain and spinal cord, from where it is reabsorbed. Anything blocking this flow, such as …

Theists and atheists can at least agree on one important statement: "There is no such thing as god" (21 February, p 54) . For the theist, this isn't because god isn't real, but because god isn't a thing. God by definition is the author and sustainer of creation; not an item within it. Faced with …

In his article on megaprojects, Michael Marshall discusses flooding the Qattara depression in Egypt (3 January, p 34) . This is an old idea that will lead to the creation of another Dead Sea. Evaporation will gradually increase the salinity of the water until a supersaturated salt lake is created. The salt water will seep …

I was upset by the bad press given to Scottish country dancing by Roger Malton (14 February, p 55) . This type of dancing should certainly not be high impact, nor cause any twisting if done in proper light shoes on a suitable floor. It is in fact very healthy exercise for both mind and …

Health minister Beatrice Lorenzin needn't worry about Italy's falling birth rate (21 February, p 8) . If each woman has 1.39 children, it will take about 49 generations for the population to fall to 1 (at which point Italians will presumably go extinct). There's nothing to fear from a lower population. Historically, Italy has always …

• An error landed in our story on meteors (21 February, p 13) : Manuel Moreno-Ibàñez is affiliated to the Institute of Space Studies (CSIC-IEEC) in Barcelona, Spain.