Letters archive

Amid calls to relax the need for spacecraft sterilisation as we seek evidence of life beyond Earth (6 July, p 8) , it's worth recalling how such efforts have fared in the past. I worked at NASA's Langley Research Center in the 1970s, and I remember the concern that many involved in the two Viking …

You report that a new measure of global prosperity, the Genuine Progress Indicator (GPI), peaked in 1978 and has subsequently been falling while gross domestic product has continued to grow (13 July, p 14) . This was about the same time that annual demand on the planet's resources exceeded its ability to provide those resources. …

Some of the issues related to the US health disadvantage raised by Laudan Aron (13 July, p 28) have also been studied by Richard Wilkinson and Kate Pickett in their book The Spirit Level . In countries and US states for which statistics exist, they found that higher income inequality leads to worse life and …

In your look at the rise of renewables, you said that geothermal energy is "just as effective as hydro and onshore wind, but limited to tectonically active areas" (6 July, p 6) . However, a pilot plant for a hot rock project in Australia recently began producing 1 megawatt of power from water heated by …

Rebranding terrorist "martyrs" as suicidal individuals as suggested by Adam Lankford is long overdue (6 July, p 24) . The use of words such as "war" and "terrorism" give them great kudos. There have been a number of studies into the impact of Israeli policies on the mental health of Palestinians: of military operations, of …

Articles on artificial day and night helping to maintain the quality of picked vegetables (29 June, p 17) and UV light keeping fruit mould-free (15 June, p 23) set me thinking. Domestic fridges could be fitted with LEDs of the right wavelength to maintain circadian rhythm, and a UV light in a fridge drawer could …

We have had the fly-in-the-urinal "nudge" (22 June, p 32) and the historic use of a bee (13 July, p 33) to influence men's aim for the better. In Slovenia I discovered a urinal with a tiny set of soccer goalposts and a ball suspended by a thread from the crossbar – irresistible! Does this …

Fracking technology has developed effective and accurate horizontal drilling to exploit fossil fuels deep underground (8 June, p 7) . This is precisely the technology that would allow the exploitation of clean, sustainable geothermal energy. There is an almost unlimited supply of this in many places; why not develop it?

In his letter, Stephen Rowe is right to say that we need to understand gravity better rather than invent dark energy to account for the accelerating expansion of the universe (15 June, p 33) . We know that quantum theory is accurate over atomic scales. The assumption that gravitational forces are the same at intergalactic …

Regarding the health costs of excessive sitting (29 June, p 44) , what's this obsession with living as if there will be no end? If I spend all my time moving, as suggested, will I also find time to create something of lasting value? Shakespeare's sonnet number 74 says it all: "But be contented when …

Hugh Lawton and Marc Smith-Evans may unwittingly be indulging in cultural imperialism when talking about download progress figures of "4,100%" and "9,800%" for MacKeeper software (Feedback, 22 June) . Where someone in the UK or US sees a thousands separator, a few hundred million in mainland Europe see a decimal point.

You mention the possibility that five other hominins co-existed in Africa at the same time as Homo habilis , each with different human-like features (13 July, p 34) . Is it also possible these hominins were close enough to interbreed and produce fertile offspring, leading to a number of them being our ancestors, rather than …

Your readers might enjoy knowing that the Rashomon software, which syncs video of street protests from multiple sources (29 June, p 22) , is almost certainly named after a 1950 Japanese cinematic masterpiece by director Akira Kurosawa. According to Christoph Koettl of Amnesty International, the software will produce a "comprehensive view" of a situation that …

• We got nuclear geophysicist Rob de Meijer's academic affiliation wrong in our look at a new theory of how the moon formed (6 July, p 30) . His correct place of work is the University of the Western Cape in Bellville, South Africa • It's not the end of the world, but Feedback really …