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Having read the tribute you published, I am reflecting on the death of Bernard Dixon, editor of Â鶹´«Ã½ from 1969 to 1979 (5 December 2020, p 26). I started reading Â鶹´«Ã½ as a very young child in the 1960s, and I well remember the improvements made by Dixon in the early 70s. It …

Although I don't consider myself to be a domestic cat lover, I feel they are being unfairly accused of decimating British wildlife, particularly birds ( 31 October 2020, p 42 ). I am not disputing that birds are killed by cats, but remember that many birds are killed during the migrating season every year when …

Your article on mass testing to control covid-19 emphasises the importance of using multiple methods to keep it restrained, and highlights the success of certain Asian countries in doing this ( 28 November 2020, p 14 ). Living in Thailand, where the infection rates have been low, it seems likely to me that the use …

The "something obvious" Matthew Allan is missing in how to steer a solar-powered space vessel is the resultant force felt by an object when light reflects from it ( 28 November 2020, Letters ). If it uses a mirror set at a non-right angle to the light as a sail, the reflected photons will create …

An equivalent of solar sailing on the sea, into which the keel bites to allow the ship to tack upwind, is gravity. The mathematics is more complicated, but sailing a spacecraft using solar wind and gravity is similar to sailing on wind and open ocean.

Further to your report on the prolonged problems that a coronavirus infection can cause, my wife was diagnosed with covid-19 in March 2020 ( 31 October 2020, p 10 ). She experienced a high temperature, sore throat, chest discomfort and breathlessness. Interestingly, a nurse said the chest discomfort in the sternum (and possibly the sore …

Thank you for your thoughtful piece about efforts to free the orca best known as Lolita from the cramped confines of the Miami Seaquarium ( 28 November 2020, p 40 ). It is unimaginable for any of us to envision 50 years in lockdown, let alone in conditions that fail to meet our basic needs. …

Sylvia Terbeck presents two versions of the trolley problem: one in which you divert a trolley that will kill five people so it only kills one other person, and another in which you push someone into the path of the trolley to stop it ( 31 October 2020, p 23 ). This addresses the problem …

Michael Le Page writes about the exciting news that an AI system has learned how to predict how proteins fold ( 5 December 2020, p 15 ). That is all well and good and I am sure it will help the human condition immeasurably, but when will the great scientific minds teach a robot to …

After reading about efforts to put a quantum twist on Einstein's theories of space and time, I think I am getting a torsion headache ( 28 November 2020, p 34 ).