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I have read your fascinating article on the phenomenon of superluminal shadows in astronomical contexts. It is truly captivating to explore these cosmic curiosities. However, I would like to point out that apparent superluminal motion isn't just confined to the depths of space( 27 September, p 42 ). Engineering equipment capable of demonstrating similar effects …

You looked at a book discussing Neanderthals' extinction at a time when a separate species, Homo sapiens , moved into their areas. Both populations were distinct prior to interbreeding, and today a vestige of Neanderthal DNA remains in our species( 27 September, p 30 ). The current genetic mix we see in Homo sapiens today …

Rosemary Sharples feels that public transport doesn't go everywhere and doesn't allow for the user's choice of time, route or travel companions, and says the most flexible form of public transport, a taxi, is the most expensive. But look at Vienna, where public transport does indeed go everywhere and is very frequent, including late into …

In your look at how to live to 100, Bryan Johnson states that he doesn't need to worry about how long he will live because it won't be long before he can upload himself to an AI( 20 September, p 40 ). This is, of course, massively optimistic, requiring not only the technology, but also …

Why was there no mention of posture in "How to live to 100"? The typical depiction of older people is of someone bent over while using a walking stick, but good, upright posture aids breathing and mobility, and helps to avoid injuries when exercising.

The idea that our brains are always on the verge of disorder seems to me to have quite limited explanatory value. Criticality in the brain may describe seizure states well mathematically, but it doesn't explain them. If it also describes Alzheimer's disease, in which there is widespread and progressive loss of neuronal function, akin to …

I concur with Robert Sugden's views. As an otrovert, I find no particular attraction in interacting with others solely because they are also otroverts. Interesting conversations come from people with different points of view. I am Russell's paradox, part of a set that doesn't include myself( Letters, 13 September ).

David Robson's article on narcissism is enlightening and a reminder that we can all get carried away with trying to appear cleverer than we are. But the final paragraph sidesteps the elephant in the room: we may well be better off without narcissists, but when we grant them power, they destroy lives and economies. Avoiding …

Congratulations! An article about narcissists without mention of a certain president!

I read your story "Quantum supremacy is here at last". Yes, I agree that the advances reported on build on ideas that have been explored for decades. But is quantum supremacy here yet? I think not. It is still beginning( 27 September, p 11 ).

In addition to improving recycling, Saabira Chaudhuri's call for standardised plastic packaging across brands for similar products could solve quite a problem for me, especially in strange stores. Very few products clearly tell you what they are for – the brand name outshines all such useful information. Standardised packaging would be a great help, along …