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It was nice to read that what was just a whisper about problems with our leading explanation of the universe is now a shout – that "our best model of the cosmos, a seemingly serenely sailing ship, might be holed beneath the water line" ( 28 November, p 34 ). Indeed. The real question arising …

As your interview with Heidi Larson suggests, it would seem that persuasion, coercion or appealing to people's better nature is unlikely to have much effect in the uptake of a vaccine against covid-19 ( 21 November, p 12 ). So how do we deal with the problem? Perhaps a system of registration could go some …

Wouldn't it be prudent to issue a secure and easily identifiable badge at the time of vaccination to show who has had it and encourage others to get the injection? It isn't as though it would take long to manufacture them.

The arrival of successful vaccines for covid-19 is great news ( 21 November, p 36 ). But if a possible outcome is a shortage of the special glass needed for the vaccine vials , has their recycling potential been considered? Borosilicate glass can't be recycled in normal waste streams . You mention an estimate that …

The trolley dilemma always puzzled me ( 31 October, p 23 ). Anyone who has played with a train set as a child knows that accidentally setting the points to the halfway position will derail the train. So, move the lever to this position, the runaway trolley is derailed and stopped, and all the people …

Regarding the Aperture photo ( 14 November, p 28 ). Despite what the text says about the birds being calm, drone photography at any nesting site mustn't be allowed.

We should have said that birds that moult all their flight feathers from both wings at once may be predisposed to evolving flightlessness ( 5 December, p 17 ).

Guy Cox, St Albans, New South Wales, Australia Your report on work to develop the first laundry detergent for use in space implies that International Space Station crew members are expected to wear their clothes until they are quite unpleasant ( 5 December 2020, p 17 ). But why wear clothes at all during regular …

Simon Baron-Cohen points out that about 100,000 years ago, a rise in empathy and in inventiveness occurred, and that the brain circuits involved in both "surprisingly" arose at about the same time (5 December 2020, p 34). He notes that in each individual, one circuit tends to dominate, and that the genes for invention are …

I am furious at the collapse of the Arecibo telescope ( 2 December 2020, online ). How was this allowed to happen? Puerto Rico is an unincorporated territory of the US, not of a low-income nation.