Â鶹´«Ã½

Tom Chivers rebuts claims by surgeon Roger Kneebone that students lack manual dexterity because they spend too much time with flat screens ( 10 November, p 25 ). When I was at the Indiana University School of Medicine in the 1970s and 80s, we built patient simulators to enhance the examination skills of medical students, …

An ion-powered plane may have lift-off ( 24 November, p 7 ). But landing a full-sized, battery-powered plane is an engineering challenge. Airliners are much lighter on landing than take-off, because the fuel tanks are empty. Overweight landings are possible in an emergency, but often lead to structural damage. A discharged battery weighs much the …

As an engineer who has spent years on electric propulsion systems for both cars and low-speed aircraft, I found the article on ionic-propulsion flight intriguing. A primary concern for electric aircraft is propulsion efficiency: thrust multiplied by speed per watt of power. A well-optimised system driving a propeller with an AC motor fed through an …

What will happen to a bird that flies into the ion drive ? The plane will be quiet, and the gaps between its wings could give the impression it is possible to fly between them.

The MIT model may well be the first such aeroplane to fly freely. But a similarly powered model , developed by veteran aircraft designer Alexander de Seversky, took off vertically and flew in 1964, albeit tethered to its power supply. It could be steered by varying the voltages applied in different places. Such direct lift …

What if the other side thinks WE'RE the dark matter? Kelly Reay develops the idea of particles crossing to our world opening a portal to a dark-matter realm ( 1 December, p 36 )

Michael Marshall discusses what is now being called autonomous sensory meridian response ( 3 November, p 35 ). I have experienced this since I was a child. I have a distinct memory of where it started and therefore how it might actually happen. My first experience of a warm, feel-good tingling, as described by other …

• Gravity waves are a feature of fluid dynamics; gravitational waves are in the fabric of space-time (Letters, 24 November and 1 December ).

The hosting of the UN climate change conference by the coal mining town of Katowice, Poland, and its sponsorship by coal firm JSW highlighted the economic dependence on coal in such countries (Leader, 8 December ). I do appreciate the importance of ultimately stopping the use of fossil fuels, but suggest that an interim step …

At the end of an interesting article on spiders' maternal behaviour, you state that milk secretion is exclusive to mammals ( 8 December, p 20 ). Another non-mammal that certainly has glands that produce brood food and feeds this to its young is the honey bee. You can buy "honey bee milk" as "royal jelly".