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Regarding the debate over the start of the Anthropocene Epoch, the era of human influence on planetary systems, perhaps it wasn't to do with geology at all. Before we created technologies that led to the Anthropocene, a change in attitude had to happen. I would pinpoint this as occurring in the 16th century, when white …

The article on how some alien worlds may lack the conditions for the discovery of fire suggests that smelting ores to extract metals is probably a prerequisite for the evolution of advanced societies. Yet it neglects the possibility of enzyme or catalyst-mediated manufacturing. For example, one of the hardest and longest-lasting materials in nature is …

Your story states: "Lab experiments have found that combustion can't fully occur in atmospheres with oxygen levels below about 18 per cent." Under what conditions of temperature and pressure does this hold? We can't assume alien atmospheres will always be at pressures and temperatures similar to Earth's.

Though I enjoyed your recent look at the standard model of particle physics, I was surprised the "How to break the standard model" section didn't mention teleparallel gravity, whose "twistors" may unify the electromagnetic force with that of gravity ( 9 September, p 36 ).

I had never heard of an atlatl, the ancient weapon in your recent story. But Australians may have heard of the rocket base developed at Woomera in South Australia , aptly named after an Aboriginal spear-launching device of the same name. This weapon is possibly of far greater antiquity than the one examined at Kent …

UK prime minister Rishi Sunak says it is OK to carry on installing gas boilers until 2035 because the lifetime of these devices means most of them will be replaced by 2050, when the country has pledged to reach net zero. Similarly, we can keep buying new fossil fuel-powered cars until 2035, instead of the …

If the lambda-CDM model of the universe doesn't seem to be working, perhaps the reason is that one of its assumptions is wrong: that the distribution of galaxies is a cosmic web. It could equally be a cosmic foam, which would look much the same. The difference would be that the voids contain an active …

Having worked on Emmerdale and other soap operas, I know Chanda Prescod-Weinstein has a point about timescales in such shows making no sense, even if she was exaggerating a bit. I can recall at least one case of a prepubescent cast member vanishing only to be replaced soon after by an actor several years older. …

You report research that says it is bad for the planet if we use more than 10 per cent of all biomass. But we can actually solve problems by harvesting biomass. This doesn't mean deforestation, but using it in a sustainable way to sequester carbon. This would cut carbon in the atmosphere, reverse global warming …

Thanks to Guy Cox for noting that, 100 years ago, chloroplasts were known to be structures in cells. In my article, I was referring to the state of knowledge in the 1920s and 30s about human cells. Outside the nucleus, the only structures known then were mitochondria, whose function was unknown, and putative Golgi bodies, …