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While New Zealand may claim some credit for the relatively early closure of its borders, it was still too slow ( 27 June, p 11 ). Nearly a month passed between the country's first known infection and lockdown. That isn't good enough. Scientists had been warning of a covid-type pandemic for more than a decade. …

Corinne Le Quéré misses an important option in her advice to the UK government on how to use the economic stimulus required after the lockdown to encourage the shift to a net-zero society ( 4 July, p 36 ). As well as the electric cars and bikes that she mentions, lockdown has shown that choosing …

You report that Scotland could eliminate the coronavirus if it weren't for England ( 4 July, p 8 ). There are many reasons why the experience of covid-19 has differed regionally in the UK. To take just one example, overcrowding has been shown to be a big issue. Scotland has the lowest population density of …

Peter Borrows wonders what will happen with the move to 1-metre social distancing as the lockdown is lifted ( Letters, 4 July ). Here is one simple answer: the dole queues will get shorter.

It would be satisfying to be able to dismiss the idea that we are living in a simulation, as earlier letters have, using the argument that it would require unfeasible amounts of energy to run ( Letters, 4 July ). Yet I am not entirely convinced. If our reality is a simulation, then the laws …

The energy-related arguments that we don't live in a simulation created by an advanced civilisation hold true if the simulating entities are also in a three-dimensional existence. However, what about higher dimensions? Up to 10 are postulated under superstring theory, for instance. Denizens of higher dimensions could be free of the energy constraints we face, …

I have watched the pursuit of fusion power for more than 50 years ( 13 June, p 30 ). However, the current approach begs a question. Half the world's population is funding one giant fusion experiment – ITER – that was designed decades ago. It relies on just one proposed fuel and is projected to …

The estimated number of people who have contracted coronavirus in the UK according to SeroTracker is 5.13 per cent ( 20 June, p 10 ). The source of the cholera outbreak that John Snow identified wasn't the water pump handle, but the water being pumped ( 6 June, p 54 ).

I share Peter Borrows's feelings on inverse square laws applying to social distancing ( Letters, 4 July ). But there is another mechanism beyond direct transfer that is relevant to stopping the coronavirus. The question of indirect transfer – inhaling contaminated air that has been circulated from a distant person – seems relatively neglected. In …

Regarding the use of water instead of argon in double-glazing, two thoughts come to mind ( 11 July, p 15 ). Firstly, wouldn't water add a fair amount of weight to each window? This wouldn't just be from the weight of water, but also from the frame and seals, which would have to be upgraded. …