Letters archive

You investigate why Australia has relatively few serious cases of covid-19 18 April, p 10 . One factor could be that, at the end of summer in an outdoor living nation, few people will be deficient in vitamin D. By contrast, in the northern hemisphere, other than in the tropics, people's vitamin D levels are …

Sam Edge is certainly right when he says that pharmaceutical firms only bear a small part of the costs of vaccine development, as "most of their work is founded on existing research..." (Letters, 4 April ). That is the way science works. Even Isaac Newton noted that he had seen further only because he could …

You report on a new study suggesting that cave bears died out at the height of the last glacial maximum 24,000 years ago because their skulls were shaped in a way that prevented them from switching to a diet of meat 11 April, p 18 . Like many similar ideas, this doesn't explain why the …

Alert readers of "Creatures of the abyss" may have wondered about the names Osedax (said to mean "bone-eating" in Latin) and Xylophaga (said to mean "wood-eaters" in Latin) 18 April, p 40 . They seem to have nothing in common, so which bit means "eat"? The explanation for the conundrum is simple: Osedax is based …

I have been advocating face masks (18 April, p11 ) for several weeks as a way of slowing the spread of respiratory infections such as covid-19 and, four weeks ago, devised an easy, home-made, five-layer mask from a folded, non-woven kitchen cloth that encloses three layers of paper kitchen towel. As well as conforming well to …

Jessica Hamzelou reports on the mixed evidence for the efficacy of the general use of face masks in the fight against covid-19. Given their use will probably become more widespread in the future, and is likely to be advocated by governments including ours, there is one situation where face masks will have a significant effect …

Your pages have been full of stories on the effects of the pandemic on day-to-day life. Here, 30 kilometres from Frankfurt airport, the virus has brought changes, too. People live, but noise has died. In the garden, where the Boeings fought a winning battle with the larks, the dinosaurs have at last reconquered Earth as …

In Australia, we had our own little green invader (11 April, p42 ): a cactus called prickly pear that was introduced in about 1787, only to become an invasive weed by the early 20th century. Then, in 1925, an insect was introduced, Cactoblastis cactorum, which ate the prickly pear and solved the problem. Cane toads, …

Tom Gauld may have a problem in finding a really good quantum mechanics cartoon (11 April, p26 ). It might not be possible to know exactly how funny a joke is and unequivocally what it is about at the same time.

Liz Berry wrote about the possibility of immunity from pathogens by eating earthworms (Letters, 25 April ). Back in the 1950s, my brother was found at the bottom of the garden rolling earthworms in sugar before eating them. He hasn't suffered from pathogens, but does have high blood pressure – presumably from all that sugar.