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I realise that it might just be a turn of phrase, but I am quite concerned about the use of "unlimited" with respect to tapping magma chambers as a source of energy. It may be an unimaginable amount, but it isn't unlimited. Ask anyone who has been in space and seen the finite size of …

Your article got me thinking about indirect contributors to the Mediterranean diet's healthful properties ( 13 January, p 32 ). Specifically, with large amounts of fresh and unprocessed foods, how many more beneficial microorganisms are supported? We are learning of the importance of our intestinal microbiome: has anyone yet compared that of long-lived Mediterraneans with …

From Letters, 13 January

Tony Green suggests that, billions of years from now, only the mega-rich will be able to afford to decamp to the moons of the gas giants to avoid the sun's expansion, while the rest of us plebs are left behind. I think he is taking too pessimistic a view about the survival of economic systems …

We appreciate your efforts to present diverse views concerning the definition and application of the Anthropocene. Nevertheless, we are concerned by the closing quote of the article, which suggests that standing against defining an Anthropocene Series/Epoch in the geological time scale, as we do, is to deny anthropogenic global climate change. As scientists and as …

When it comes to dark skies, Aotearoa (New Zealand) aims to be the world's first dark sky nation , a fact that warrants a mention. It is a lofty goal, but the country already has five dark sky reserves to enjoy while we wait for this to happen ( 6 January, p 28 ).

You report that beeping shoes boost walking ability in people with Parkinson's disease. Around 40 years ago, I was working with people on the autistic spectrum, one feature of which can be difficulty feeling the ground you walk on. When a colleague of my husband's got Parkinson's disease and was having difficulty walking, I suspected …

You report on the issue of organic waste generated by cod fishing. When I visited the Lofoten Islands in Norway, cod waste was turned into fertiliser. A little forklift trundled back and forth all day feeding cod heads, bones and skin from the fish finger factory into a fertiliser plant. It smelled horrible, but the …

The idea that the brain may exploit quantum effects in its operation left me with a profound sense of "so what?" Consciousness, however defined, is a phenomenon of the mind, which is embodied in the central nervous system. This is a biological entity, that relies on chemical and electrical processes, which themselves arise from quantum …

When archaeologists are confronted with observations for which they have no clear explanation, they often tend to attribute religious, or symbolic, significance, as with the straight roads between settlements found in the Ecuadorian Amazon. Might it not be that for some mundane, technical reason, such as a mode of transport, the roads needed to be …