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Stephen Battersby is unfair to Albert Einstein in saying his relativity theory fails if Sagittarius A* turns out not to be a black hole (23 May, p 28) . At the British Gravity meeting in April, long-time guru of black holes, Kip Thorne, reminded us that J. Robert Oppenheimer and his student Hartland Snyder predicted …

Linda Geddes's review of End of the Line , a documentary on the effects of overfishing, hits the mark (6 June, p 48) . For decades, the marine environment has been damaged by over-exploitation. The lesson to take from End of the Line is that unregulated fishing cannot continue. This film comes at an extremely …

The recent opinion piece by Edzard Ernst fails to give a balanced view of chiropractic (30 May, p 22) . Since its origins in the middle of the 19th century, chiropractic has changed considerably. It no longer espouses a vitalistic philosophy. Equally, conventional medicine has changed and no longer bleeds dehydrated cholera patients to death. …

While it is likely that there was less public support for the wars in Vietnam, Afghanistan and Iraq than for the first and second world wars (16 May, p 26) , Stephen Wealthall wrongly assumes that this is reflected in prevailing attitudes in the military. As Wealthall states, the majority of world-war veterans did not …

Prompted by your essay on C. P. Snow (2 May, p 26) , David Roser commented on the poor communication between related disciplines at his university (30 May, p 20) . I am a first-year student studying anthropology, sociology, psychology and philosophy. All the courses deal with concepts of "the person", but with little overlap. …

David Attenborough uses the example of termites working blindly in a nest to illustrate that humans may also lack a sensory mechanism – the one they need to perceive a creator (16 May, p 28) . However, should the termites sense him, there is no reason why they would impute him to be their creator, …

In her article on medical research into death by fire, Linda Geddes states that it is a myth that bodies usually sit up as they burn (23 May, p 32) . As an apprentice electrician in the mid-1950s, I was working one day on a thermostat control in a newly built crematorium. An operator directed …

Frederick Blundun argues that an intelligent being would inevitably develop Newtonian dynamics (23 May, p 25) . However, the universe experienced by a microscopic or nanoscale intelligence would be dominated by fluid dynamics, chaotic turbulence and fractal boundaries. They would be likely to develop a theory of relativistic quantum dynamics long before they developed the …

I was fascinated by the link found between brain physiology during conflict and post-traumatic stress disorder in soldiers, reported by Peter Aldhous (9 May, p 40) . Is it possible that potential interventions and treatments mentioned in the article could be applied far more widely? I suggest that most mental distress, unless drug related, is …

Never mind Ray Kurzweil's singularities in 2045 (9 May, p 26) ; when will we all have personal helicopters and more leisure time? Any futurologist who doesn't promise these isn't playing the game properly.

• We mistakenly suggested that greater gender inequality increases the instance of female mathematicians in a country. Of course that should have been gender equality (6 June, p 7) . • Some corals live in water flowing at a rate of 10 metres per second. However, we should not have implied that this was a …