Letters archive

From From David Muir, Edinburgh, UK It was good to read about the advances in direct air capture of carbon dioxide. However, the purchase of offset carbon credits by large corporations on the back of this strikes me as nothing more than a licence to pollute. Such firms should be doing more at source to …

Scaling up direct air capture (DAC) raises many questions. How will the giant new plant be powered? In other words, how much carbon dioxide will be released into the atmosphere to power this plant? What's more, how long will such plants need to operate to remove the same amount of CO 2 that was released …

Considering that the world's terrestrial vegetation absorbs some 12 gigatonnes of carbon dioxide every year, wouldn't it have been better to not invest in this plant, but to grow more trees instead? Also, let's stop burning existing trees – allow them to live a full life, then turn them into useful products, so this CO …

I was struck by the juxtaposition of the article on the use of CRISPR technology to create disease-resistant pigs and another piece urging us to consider the welfare of AI chatbots. This highlights a troubling inconsistency in our ethical priorities. On the one hand, we are developing tools to intensify pig production, perpetuating a system …

No one has yet proven that artificial intelligence in its true sense even exists. In fact, there are many reasons to say that it doesn't, including the fact that no "AI" has yet demonstrated critical reasoning. Starting to talk about the rights or welfare of AI is therefore utterly ridiculous.

In your ultimate guide to skincare, David Robson says that showering a few times a week may suffice to keep the body's outer layer in good condition. Speaking as an older reader who didn't encounter a shower in someone's home until the age of 18, I can assure him that showering zero times a week …

If weight loss were to occur as a side effect of using semaglutide to treat heart disease, that might not always be a good thing. I am talking about for treating older people, who may be severely underweight already. Weight loss wouldn't be healthy there ( 11 January, p 19 ).

Cities like Singapore, Tokyo and Hong Kong enjoy relatively low crime rates and long lifespans despite population densities 100 times the planet's average – hardly evidence of a John Calhoun-style breakdown due to population growth. There are problems due to overpopulation, but not of the sort he predicted ( 14/21 December 2024, p 52 ).

It is wrong to claim that Calhoun's forecast of social breakdown in an increasingly crowded world "hasn't (for the most part) materialised". It seems to me that Earth's population is indeed in the middle of its "behavioural sink" and unfortunately appears likely to destroy itself.

A lunar colony would be far preferable to one on Mars. Its foundation is within the ambit of modern technology, and it could be rapidly serviced from Earth. The moon has many valuable resources, including water, which could be used alongside excellent solar power generation, unaffected by dust storms as it would be on Mars. …

Keeping a Mars colony going as a useful backup for humanity would be astronomically expensive, and you would need to continue this for thousands of years, just on the off-chance of something truly awful happening on Earth. It is a childish distraction from the less glamorous but more important problem of adapting to live on …

We are urged to try the writing of philosophers, such as the "impeccable logic" of Bertrand Russell, as a remedy for poor fact-checking in popular science books. Turning to Russell's 1948 book Human Knowledge: Its scope and limits , we read that "helium... has a nucleus consisting of four protons and two electrons" ( Letters, …