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Michael Le Page discusses the potential of very large-scale desert solar and wind farms to increase local rainfall and hence vegetation ( 15 September, p 16 ). And UN secretary-general AntÓnio Guterres declared on 10 September that we are at a defining moment for avoiding runaway climate change. It seems we have a critical need …

Yvaine Ye reports on using sound pressure to create a bubble from a levitating droplet ( 22 September, p 19 ). Five years ago Jacob Aron described similar levitation using sound, creating a standing sound wave in which gravitation and acoustic forces cancel ( 20 July 2013, p 10 ). Levitated objects could be moved …

Pascal Boyer assembles a convincing array of observations on how the general population doesn't understand the economy – or, at least, on how it doesn't share the same understanding as the economists he is familiar with ( 22 September, p 40 ). But behavioural economics has fairly comprehensively killed the idea that we behave anything …

Your article on folk economics states that the "wealth pie" being finite is a flawed idea. This is far from self-evident. We have one planet, and we don't account for negative wealth such as forest loss or damage from climate change. Another of the "flawed ideas" discussed is that sellers can fix prices. But corporations …

Boyer allows no room for the sort of redistributive taxation policies that from 1945 to the early 1980s helped to narrow the gap between rich and poor in the UK. Since then, right-wing taxation policies have been reopening the gap, to the detriment of the country as a whole. Yes, that's a left-wing view, but …

Adam Smith argued in his Wealth of Nations that for free markets to work, employers must not be allowed to confer. And "free" markets are in fact highly regulated, to prevent adulteration of food, for example. That does happen without regulation. And consumers cannot choose lower prices if no companies offer them.

Boyer says that it is as if the human mind is designed to misunderstand mass-market economics. But retroactive maladaptation would be hard to explain. I offer a counter-proposal: it is as if mass-market economics is designed to be misunderstood by human minds. This is easy to explain. Those in charge of such economies have a …

Congratulations to Enid Smith for blowing the whistle on washing machines that accept only cold water (Letters, 8 September ). We live off-grid, running on solar power, and our only water supply is what falls on our roof. When we went to buy a washing machine, the only one with a sufficiently low power consumption …

Smith writes that she was unable to find a washing machine that took warm water from the domestic system. The fact that washing machines need high-pressure water used to mean there was no option but to connect them to the cold water supply. Many houses now have high-pressure hot water systems. If her solar panels …

Clare Wilson reveals some of the earliest known human mark-making, possibly pushing back the beginning of the history of art ( 15 September, p 7 ). I am irritated, though, by the use of "etching" instead of "engraving" or "incising" to describe how the marks were made. The distinction is important to me as an …