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You report a study claiming that decreased physical activity during the first covid-19 lockdown in England may lead to increased obesity 8 May, p 10 . But I have recently read several convincing articles in Â鶹´«Ã½ showing evidence that there is little correlation between exercise and weight change when measuring over periods longer than …

Reading Stephen Fleming's article on self-reflection, I realised there is at least one training exercise that might improve metacognition – the ability to think about our own thinking – that millions of people do every day: crosswords 8 May, p 36 . How well does your answer fit the clue? Is it the right length? …

Nearly 60 years ago, I had an argument with the curate taking our bible class 1 May, p 39 . I thought the grove of silver birches outside might be conscious and able to communicate with each other; he wouldn't have a bit of it because, he told me, the bible said only humans could …

To add to James Wong's thoughts about the colour of watermelons historically, there is more evidence from the 14th century that the inside of the fruit was red then 24 April, p 22 . Moroccan scholar Ibn Battuta travelled throughout Eurasia. He loved his food and observed that Khwarazm, south of the Aral Sea, produced …

Thank you for your article about the fight to eradicate malaria 1 May, p 44 . Quite apart from reporting the success in tackling that terrible disease, you included a statistic that at any time would be a source of hope, and especially now. Anuradha Gupta's quote saying that, compared with two decades ago, we …

You report on a survey that found 29 per cent of people in England decreased their physical activity between March and August 2020 amid pandemic lockdowns ( 8 May, p 10 ). I assume there is a correlation between physical activity and life expectancy. So the survey could mean that up to 29 per cent …

That we have begun a new geological epoch, dubbed the Anthropocene, seems not to be doubted by anyone, but Adam Vaughan tells us that pinning down its defining feature appears to be troublesome ( 8 May, p 12 ). The problem is that, whereas all the other recognised epochs were defined with the benefit of …

In your look at efforts to address the dominance of some tech companies, John Bergmayer is quoted as saying: "You don't just have one big, global telephone company for Earth, but that's kind of where we are with Facebook ( 1 May, p 34 )." That is a poor comparison. Telephone, the post and email …

The discussion of an ultra white paint to cool buildings in summer sparked a reader to worry it might do this in winter too, meaning we have to turn up the heating ( Letters, 15 May ). Physics says otherwise. In winter, a white surface will radiate less heat, helping to keep the warmth in.

It is a mistake to suggest that, just because animals may not necessarily have our kind of intelligence and consciousness, they therefore don't have it ( Letters, 1 May ). Creatures as disparate as the day octopus, manta rays, corvids and great apes all have the necessary neural substrates to support cognitive processes and all …