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You report that we are roughly in the centre of a very rare void in the universe that doesn't match our cosmological theories. What else seems to be vanishingly rare in our part of the universe, roughly in the centre of the void? Life. (20 April, p 36) That is either an impressive coincidence or …

Clearly, the reason that the Milky Way is near the centre of a cosmic void is that no other advanced life forms want to risk their worlds getting infected with Earth's planet-destroying virus. They aren't yet sure if it is catching, so they are keeping their distance.

The increasing frequency of heavy rainfall events in the United Arab Emirates – like the one we saw recently, probably driven to some extent by rapid climate change – may reduce dependence on energy-intensive desalination, which is currently a key source of drinking water in the region. ( 27 April, p 16 ) Interconnected underground …

If you eat meat, researcher Anthony Hulbert recommends you have grass-fed beef or lamb and wild-caught fish, as they are high in omega-3s, and avoid pork and chicken because they are high in omega-6s. I rarely eat fish as I don't want to contribute to the destruction of aquatic wildlife, and I avoid beef and …

Graham Lawton can count me as a staunch fan. I agree with him that it is self-deception to imagine that he offset much, if anything, of his flight-related carbon dioxide by crossing a greenwashing scheme with a tiny piece of silver. This doesn't mean it is impossible ( 11 May, p 22 ). I fly …

Has Lawton considered that his carbon offset certificate's "1.69 mt" might actually be a correct use of the prefix "m" and mean that he has paid to offset 1.69 millitonnes of carbon? He could probably do a better thing for the environment if, instead of paying into a rather opaque "carbon offset" market, he visited …

Jan Zalasiewicz implies that the mass of evidence of human impact on the Earth system was rejected in the recent vote by geologists over the Anthropocene. Actually, few scientists would dispute that substantial body of evidence. What was rejected was the specific proposal that the start of the Anthropocene epoch should be placed in 1950 …

Katie Steckles's article about "Pythagoras in the wild" reminds me of an interesting experience of encountering maths when buying cake tins. I got two "catering-sized" square ones from a commercial baking supplier. I was intrigued by the dimensions: about 360 millimetres per side. That figure didn't seem to mean anything special. Neither did the equivalent …

Several readers have voiced optimism about reaching a new economic equilibrium in a world where each generation is smaller than the previous one ( Letters, 20 April ). However, such an equilibrium would be only temporary. Once the world population falls to, say, half a billion, no one is building a new particle collider or …

From Butch Dalrymple Smith, La Ciotat, France Chanda Prescod-Weinstein laments the difficulty of seeing the night sky due to modern lighting. There is one group of people who can still appreciate it with no problem: sailors ( 4 May, p 22 ). On the ocean in a sailing yacht you experience the heavens at full …