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You report that ingestion of microplastics by mice changes their behaviour in the face of a deadly corn snake. After being given food contaminated with plastic, they failed to treat the snake as a threat( 10 May, p 38 ). Would it be too cynical to speculate that the lack of concern over the past …

From 22 March, p 30

Jon Cartwright points out "that string theory was so flexible it could describe a truly vast array of fantastical universes. Something like 10 500 in fact – a number so huge it belied any physical comparison". I recommend taking a look at protein folding, in which there are reportedly 10 500 potential folding possibilities.

Mark Lynas's article on the risks of nuclear war was refreshing. The threat of annihilation hangs over us every second of every day, but it seems that politicians and the media prefer to pretend it is all OK( 24 May, p 21 ). As a design engineer, I know too well the impossibility of developing …

While Lynas's hopes and wishes are admirable, with Vladimir Putin threatening the use of nuclear weapons and Donald Trump promising to "drill baby, drill", I fear that the Fermi paradox is secure in its implication that technological civilisations tend to destroy themselves in short order, and that nuclear war and climate change are inevitable. Maybe …

UK governments have long favoured multilateral nuclear disarmament. However, it always seems to boil down to: "You first."

You rightly threw cold water on the romanticism of colonising Mars. Sci-fi offering The Expanse was mentioned as a tonic to such visions. Its Martian colonists sensibly began to flee the Red Planet as soon as green worlds became available (thanks to alien tech). Why abandon our own green world for a hellscape?

Surely what is beneficial in maintaining a healthy brain is continual stimulation via all the senses, not just smell. Some stimulation, such as studying and practising a second language, may be more effective, but only long-term research will elucidate their relative effectiveness. That said, the benefit of developing the olfactory sense looks promising, and little …

So pleasant smells can help reduce chronic inflammation, and being able to smell unpleasant things can help us avoid health threats and stimulate the immune system when necessary. There is also evidence that a declining sense of smell or its loss may be addressed by regularly exposing people to a wide range of scents. However, …

You report a study that suggests an optimal way to chop onions without crying. Forget slow cuts with sharp blades, black spray paint, electron microscopes and such like – just slice the top and bottom off the onion, soak it in water, chop. No tears. Easy-peasy( 24 May, p 12 ).