Letters archive

You report that spraying salt water into the atmosphere over the Pacific to brighten clouds for nine months a year for 30 years to save California from extreme heat could eventually cause dire temperature increases in Europe as a side effect ( 29 June, p 11 ). However, other studies are more hopeful about such …

The idea of our cosmic insignificance is a matter of emotion rather than reason. We all feel it, but it does, after all, involve equating physical size with significance. This is absurd, as we don't say an elephant is more significant than a human, or a mountain than an elephant. What happens is that, when …

When it comes to our "cosmic perspective", there is one aspect of our existence that I find deeply significant. We are composed of matter and energy that has become capable of thinking about and describing matter and energy. Thus, through us and any other technologically advanced beings that may exist, matter/energy – and, by extension, …

The article "Digital damage?" misses the real danger to children from screen time – the extremely sophisticated marketing that sucks them into ruthless games that have no socially redeeming value. They are being purposely led deeper and deeper into a highly cloistered digital environment and away from being able to develop discrimination regarding how they …

You write about the singularity, the "infinitesimal point of infinite density" within a black hole. The concepts of infinitesimally small and infinitely large are extremely powerful in pure mathematics. But is their use acceptable in trying to model the physical universe? ( 15 June, p 32 ) At the centre of a black hole, the …

What a magnificent photograph of the Milky Way seemingly emerging from the summit of Aoraki/Mount Cook in Aotearoa/New Zealand. In it, our galaxy also seems to be looking down on the rapidly retreating terminus of the Hooker glacier and the equally rapidly expanding Hooker Lake. By 2016, this lake had lengthened from nothing to 2.5 …

You outline research showing how varying stride length while walking helps burn more calories. However, it does more than that. It enhances muscle tone and overall fitness. This is the idea behind fartlek, a training method for runners. Practitioners vary their pace (and thus their stride length) while running through woodland or open country, switching …

You raise the idea of paying people to lose weight. Use of financial incentives isn't new. American football player William "The Refrigerator" Perry had a clause in his contract with the Chicago Bears stating he would be penalised if his body weight went above a certain level ( 29 June, p 12 ).

When it comes to obesity, some people claim healthy food costs more. This is false. I cook all my food, mostly vegan, and it costs just a fraction of what most people spend on their unhealthy food.

There is one vagus nerve on each side of the human neck ( 29 June, p 19 ).