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As a cyclist who has ridden in many cities and countries over the decades, I have learned not to trust any driver. But I have to disagree with Matt Sparkes in his hope that AI-controlled vehicles might reduce danger on the road. Drivers instinctively recognise me as a fellow human. There is no way an …

I greatly appreciated your article on lesser-known food allergens. For some 70 years, I have experienced heart palpations and projectile vomiting when I eat cheese, but I don't have an adverse reaction to milk or yogurt. As cheese doesn't appear separately on the UK Food Standards Agency's list of allergens that must be highlighted on …

I understand Merten Reglitz's argument that internet access should become a human right. However, spending the best part of half a trillion dollars on this wouldn't automatically give people access to clean water, enough food, basic healthcare or the means to make a decent living to pay for these things, which they might consider a …

It is very refreshing to read Sophie Attwood's comments around the (often unwarranted) assumption that "natural" materials are automatically better than "modified" or "synthetic" versions. My response to people telling me that something is "totally natural" in this context has always been: "So is arsenic, but it's still going to kill you( 30 August, p …

Your article on infinity deals with very large and very abstruse concepts of it. But what about smaller, everyday infinities? The number pi is something we use often enough, but it can only be expressed accurately with an infinite series of digits. This doesn't make it large – we all know that 4 is a …

Could it be that the number zero is another infinity? Does a perfect vacuum exist? Does absolute zero temperature really exist? It seems to me that both the physical and the mathematical worlds are bounded by at least two infinities.

Regarding David Robson's piece on how bosses tend to exploit their loyal employees: in my career in the National Health Service, I often worked with newly qualified therapists who didn't feel they could say no to anything managers asked and were in danger of early burnout. I advised them to say: "Yes, I'd love to …

Almost all of the problems with the mining of minerals vital to renewable technologies like electric cars can be solved by newer technologies: zero-rare-earth magnets, zero-rare-earth electric motors, zero-lithium supercapacitors( 23 August, p 36 ). The only remaining requirement will be copper. It is even possible that a form of carbon could replace copper in …

Jupiter's moon Ganymede could be used to detect large dark matter objects, which are likely to be composed of many particles ( 23 August, p 8 ).

While reading your article on the potentially unstable brain, I was reminded of a close parallel: controlling the Eurofighter Typhoon, a modern jet fighter. In essence, the plane is aerodynamically unstable and requires computer input to function. However, the gain is that the plane is more manoeuvrable and more agile. The key point is that …