Letters archive

The complex issues of robot war that Chris Baraniuk discusses (15 November, p 38) can be boiled down to three questions. First, do we accept the utilitarian principle that we should choose the option that maximises good and minimises harm, rather than being driven by absolute principles? Second, do we agree that violence is the …

Chris Baraniuk discusses whether robot weapons should be banned. There is a long history of bans on new weapons technology, but most have met with little success. As early as 1139, Pope Innocent II, agreed to ban the use of the crossbow against Christians. Richard I failed to differentiate between Christians in France and Muslims …

The implicit assumption in your article is that robotic weapons would be deployed against human combatants. This ignores the facts about arms acquisition in the modern world. In many conflicts, the same manufacturer may ultimately have provided the weapons used by both sides. This was the case in the 1980 war between Iran and Iraq, …

Tiffany O'Callaghan explores fears that reading on screens will have detrimental effects on the development of literacy skills (1 November, p 40) . It's unfortunate how many people hold strong positions on this, given that we have "such a shallow knowledge base", as researcher Anne Mangan notes. This is opposite to my own concerns, about …

As a recent biographer of John George Haigh, the "acid bath murderer", I was interested to read Erwin Vermeij's article on the science of dissolving bodies (8 November, p 44) . I would take issue with two points, however. First, Haigh was only convicted of killing one person, Henrietta Helen Olivia Robarts Durand-Deacon, although he …

Why does anyone suggest, as Paul Younger does, that divesting from the fossil fuel industry would cause more fuel poverty (15 November, p 26) ? Fossil fuel exploration subsidies in the UK total £750 million a year on average, largely as a result of tax exemptions for oil and gas activities in certain types of …

In justifying his stance against divestment, Paul Younger mentions that our plastics rely on fossil fuels. Surely when oil is made into plastic, the oil should not be referred to as a fuel – fossil or otherwise. It is more akin to "plastic ore" in the same way that iron ore is used for making …

I was very pleased to read your articles exploring the Transatlantic Trade and Investment Partnership (TTIP) ( 1 November, p 32 ). I live in New Zealand, where a similar trade deal, the Trans-Pacific Partnership (TPP) agreement, is being negotiated for the region, likewise undertaken in near-total secrecy. No useful information is coming from the …

Whatever one may think of the hermit thrush, nobody who has listened to Australian butcherbirds can doubt that birds make music (8 November, p 12) . Their varied songs can all be transcribed – both pitch and rhythm – into Western notation. Many Australian composers have used their songs, and Brett Dean even incorporated an …

Jan Zalasiewicz ponders whether human action has pushed Earth into a new geological age (8 November, p 26) . Discussing anthropogenic changes like new minerals (concrete being an example), one other unique long-lasting material was omitted – plastic. This material is possibly more widespread than any. With that in mind, we could call the new …

I was deeply shocked to read that the Intergovernmental Panel on Climate Change (IPCC) calculated emissions must be "capped at 2.9 trillion tonnes to give a 66 per cent chance of avoiding global warming of more than 2 °C", widely held to be the threshold for dangerous climate change (8 November, p 8) . By …

Steve Orchard illustrates the inefficiencies of storing excess wind power as compressed air (15 November, p 31) . Compressed air isn't the best option for storing energy unless one has a proper use for the huge quantities of very cold air that will be available when the bottled air is released. Combining wind-powered air compression …

Looking at the difference between skinny and larger people, Linda Geddes comments that inactive skinny people move about more during the day, but may also burn more calories at night (15 November, p 32) . Perhaps this is also due to moving about more? Individuals' movement during sleep varies enormously. In our house, the skinnier …

Michael Slezak refers to the widespread coral bleaching seen during the last spike in ocean temperatures as evidence of the harm these changes have caused (15 November, p 8) . However, coral bleaching – the expulsion of symbiotic algae by the coral – is an adaptive response, akin to sweating in humans. In most cases, …

The illustration accompanying your piece on the first run of historic quantum software (1 November, p 10) was captioned with the phrase "Testing, 1, 2, 3". But surely it should have been "0, 1, both"? Berlin, Germany

• Flight of fancy: we referred to Lynn Rothschild as creator of a biodegradable drone; in fact she led the team that created it (15 November, p 21).