Letters archive

Richard Hemingway's letter suggests there is a connection between obesity and global warming (10 August, p 31) . Last year, Anna Gryka and colleagues at Robert Gordon University in Aberdeen, UK, calculated that if all obese and overweight people lost 10 kilograms, global carbon dioxide emissions would fall by 0.2 per cent ( International Journal …

Anything that diverts attention from the road ahead, no matter how briefly, increases the risks when driving. So reader Andrew Lockley's suggestion that texting is safe because it is quick and may avoid detours leaves me a little incredulous (3 August, p 30) . How many texts are likely to be sent during a journey? …

You are quite right to highlight the danger of drivers being distracted, and the safety benefits of un-distractable autonomous self-driving cars (20 July, p 3) . My all-time favourite distraction is a massive illuminated government sign, well off drivers' normal eyeline, warning that "distracted drivers are dangerous drivers". Did someone let the work experience novice …

Amanda Gefter's presentation of efforts to eliminate infinity was well written (17 August, p 32) . It reminded me of the furore that greeted philosopher Ludwig Wittgenstein when he confronted the use of infinity and the infinite in mathematical propositions. In dissecting Cantor's theorem, Wittgenstein took a view that is eerily similar to the points …

While the achievements of machine learning are impressive, it is too soon to call artificial intelligence a solved problem, despite Douglas Heaven's optimism for new approaches (10 August, p 32) . When a computer finally scraped a win at chess over Gary Kasparov, no one mistook it for AI, and Kasparov was doing almost as …

Anil Ananthaswamy mentions the world's oldest temple at Göbekli Tepe being perhaps linked to the sudden appearance of Sirius, the dog star, at about the same time (17 August, p 14) . I suggest an expansion of this view. Almost all hunter-gatherer societies have a religious specialist, often called a shaman. These might plausibly maintain …

Tim Birkhead's Instant Expert on avian senses was excellent (3 August) . His discussion of navigation made me wonder what happens to migratory birds when Earth's magnetic field flips. Stockport, Cheshire, UK

My wife and I looked after two gulls with incurably broken wings for 16 years. We usually fed them relatively expensive cat food, but once I threw them a cheap brand. The gulls dashed towards it, then stopped 2 metres away and went to the back of the garden. At the time we were puzzled, …

John Hardy's call to ban boxing (10 August, p 26) inadvertently suggests a less dictatorial solution: a ban on boxing gloves. These were originally introduced to protect the faces of rich young men who would pay to go a few rounds with the champions of the day. As gloves became heavier, boxers began defending their …

Surely your report on cryptography and quantum entanglement is quoting a key law of sympathetic magic, as set out by James Frazer in The Golden Bough : things once in contact continue to interact at a distance (20 July, p 15) . And Jacob Aron's piece in the same issue on levitating particles that move …

Linda Geddes's article on the medical potential of manipulating the vagus nerve (17 August, p 12) brought to mind something I learned as a student in 1960. The auricular branch of the vagus nerve is also known as the Alderman's nerve. This is apparently because the nerve's role in encouraging peristalsis – the movement of …

Feedback and reader Roger Christie were correct when discussing the relativity of a 55-minute BBC Science Hour radio show (20 July) , contrary to Jay Pasachoff's letter (17 August, p 31) . A radio listener moving in space will have to constantly retune their radio, if they are moving relative to the transmitter and even …

Steve Elliott was surprised to learn that heat pumps can "operate at 300 to 400 per cent efficiency" (Feedback, 20 July) , but was reassured by reader Barry Manor (10 August, p 31) . However, what Manor describes is the coefficient of performance, a measure of the efficacy, not the efficiency, of the heat pump. …

I can't see much call for a beefburger made from lab-grown meat that costs £250,000 (10 August, p 10) , but I can see a demand for more exotic varieties. How about mammoth burgers created from a single preserved stem cell? And, taking it to extremes, with a single stem cell donated by a celebrity: …

If alternative sources of protein such as synthetic meat can offer significant environmental benefits over more direct ways of exploiting vegetable protein, then they may be worth further investigation. If not, perhaps people such as Sergey Brin of Google fame, who funded the lab-grown burger, would be better off putting their money and talents into …

• Our report on Icarus Interstellar's Starship Congress went into a bit of a spin (24 August, p 8) . The organisation was founded in 2011; Philip Lubin's calculations refer to a 100-kilogram, not a 10-kilogram craft; and a radioisotope thermoelectric generator is a power source, not a fuel source. • As beneficiaries of hindsight, …