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I was very concerned reading your piece on the use of the keto diet as a treatment for anorexia. This diet has the potential to cause serious harm to someone with, or at risk of, an eating disorder ( 13 June, p 28 ). The study your story references is a feasibility trial, which isn't …

As an introvert, I don't have a wide social network. After reading various studies on superagers that recommended socialising, I wondered if I need to spend more time doing so to keep sharp ( 20 June, p 38 ). However, after more research, I found that a lot of intelligent people kept working into their …

You discuss the threat of fully autonomous weapons, programmed to kill without human intervention. In a previous era that saw the rise of a new and horrific way of killing – the spread of nuclear weapons in the decades from the end of the second world war – there was an interesting political development. A …

Your leader's question of "whether a human should always be involved, ultimately responsible for the decision to pull the trigger, or whether machines can be allowed to act alone" assumes that there is a distinction. Yet in both cases, someone has made the decision to build and deploy the killer robots. Even when machines are …

Writing in response to my letter about travelling to the TRAPPIST-1 system (6 June), Bryn Glover is, of course, completely right when he says that it would be practically impossible to get there while taking all your propellant with you in a 1 g spaceship ( Letters, 27 June ). So, how about scooping it …

Glover says "I can't imagine how to calculate the mass of fuel that would be required" for a trip to TRAPPIST-1 and back. Surely all you need is the Tsiolkovsky rocket equation, which expresses the relationship between a rocket's mass and the propellant required to move it, plus some assumptions about the astronauts' needs for …

Regarding the subjects of your book of the week, Steve Brusatte's The Story of Birds , I'm so happy to live alongside them in the bush on the outskirts of Wellington, especially the blackbirds. I often imagine them as dinosaurs, scuttling around very close by and doing raids to get food ( 13 June, p …

The distribution of the 100-odd moons in the newly discovered Mundilfari group around Saturn reminds me of the distribution of individual shots on the paper target sheets I used to check my progress when learning to handle a shotgun as a boy on the family farm. I recall that the target sheet was about 30 …

In Close Encounters of the Third Kind , Roy Neary lives with his wife and three children ( 20 June, p 26 ).