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James Ball discusses some reasons why people are nervous about new technologies ( 19 February, p 27 ). Here is another: risk. Some technologies, such as the burning of fossil fuels, come back to bite us. We deploy new technologies globally and rapidly with no idea of the long-term consequences. The internet brings benefits, but …

While Catherine Collins rightly highlights fossil fuel emissions and overfishing as the sources of coral reef destruction, rejecting coral gardening is like denying the usefulness of a bandage in protecting a wound while it heals, or cancer surgery while we lack a cure for the disease ( 5 February, p 27 ). We need to …

I can imagine that we humans influence space-time, but not that we create it, as you suggest in your new perspective on quantum reality ( 5 February, p 38 ). Who created space-time when humanity didn't exist? I always had difficulty with Schrödinger's cat. For me, it is clear that the cat is either dead …

Adam Vaughan's excellent review of ways of removing greenhouse gases from the air didn't mention biochar production, which could be deployed at scale ( 19 February, p 20 ). Pyrolysing (heating at high temperatures) organic materials under anaerobic conditions creates charcoal, which is called biochar when pulverised to gravel or dust-sized pieces and used as …

To paraphrase the journalist H. L. Mencken, "for every complex problem there is an answer that is clear, simple, and wrong" ( 12 February, p 38 ). So it is for materials and the circular economy. Consider two options. Produce 350,000 tonnes of very sophisticated materials, fabricate them into solar panels, then mount on metal …

I read again that 30 per cent of food is wasted. It is high time to bring back the pig to its rightful role of converting food waste into edible protein and fat. I know that the veterinary profession, of which I am a part, has been against swill feeding for decades, but this must …

A particular nuance of happiness has been overlooked ( 22 January, p 38 ). In her novel A Closed Eye , Anita Brookner touches on it when one of her characters reflects thus: "Happiness was what young people wanted; at his age he knew that comfort was more important."

The frequent discussions about converting land to forests in order to sequester carbon are missing something if they merely focus on using animal pasture to do so ( 19 February, p 20 ). In the UK, large chunks of land sitting unproductively under concrete could be used for new woodlands: car parks, both public and …

As someone who has suffered with chronic pain and repetitive strain in my 30s and 40s, I read "Are you sitting comfortably?" with great interest. However, can I question the usefulness of the main trial quoted in the article? This was done with 17 to 22-year-olds. Surely such a young, fit and flexible population isn't …

As a sixth-form student, I was struck by your report that routine cervical swabs can also identify ovarian cancer and potentially also individuals at risk of developing this serious disease ( 12 February, p 23 ). Due to the early success of the human papillomavirus (HPV) vaccine, there has been a fall in the incidence …