Letters archive

The use of hyperbaric chambers as a humane method to render chickens unconscious before slaughter (9 November, p 14) brought to mind my flying training. A group of us were put into a decompression chamber to learn how to recognise the signs of hypoxia before we passed out. We wore oxygen masks, and the operator …

The vacuum technology described in your article about chicken slaughter reduces the oxygen concentration to lower levels than required for life. Coincidentally, it also reduces the CO 2 levels, and it is this that avoids suffering. A similar result could be achieved by subjecting the animals to an atmosphere of pure nitrogen, so letting their …

Your look at the paradox of why women in wealthier nations tend to have fewer children included social psychologist Kristina Durante's finding that women living in US states with a low proportion of men tend to have highly paid jobs (26 October, p 46) . This is perhaps not surprising. However, her suggestion that this …

In Michael Slezak's article on time, what a delight to find cosmologist George Ellis arguing that "the passage of time one of the most fundamental features of daily life" and "the whole process of doing science depends on time rolling on" (2 November, p 34) . If physics thinks it has killed time, good luck …

One thing you can be sure of, when you've lived many years, is that while "now" may not exist much longer, "then" always will. Austin, Texas, US

To add to Slezak's uncertainty over the meaning, and indeed existence, of time, I was taught that "time flies like an arrow, but fruit flies like a banana". Southampton, UK

Douglas Heaven writes about the spooky illusion created by staring into a mirror in poor light (2 November, p 39) . He seems to be describing "scrying", known since medieval times. It was done using a polished surface, such as a sword, mirror or crystal ball, in low light. The resulting facial distortion was ascribed …

Jonathan Seagrave backs tree planting on unused farmland to capture carbon (2 November, p 32) . If only it were that simple. In Scotland it is difficult to find land or financial support to plant native trees to provide multiple benefits, including carbon sequestration, because of competing demands for crop growing or livestock grazing. And …

One of the dangers of Gaia theory – that life steers the environment in its favour – is that we might be tempted to rely on it as a sort of omnipotent safety net that will save us from any mess the planet gets into. Luckily, your recent article (26 October, p 30) pours doubt …

You report on a Mozilla Firefox browser plug-in called Lightbeam, designed to reveal the numerous websites which grab data when you browse (2 November, p 23) . However, going a step further would be useful. The old firewall program Zone Alarm Professional version 7 could not only detect all these data grabbers, but also allow …

Hugh Newbury writes that turning off a self-aware robot would not be considered murder (2 November, p 32) . Surely the more relevant question is how one would respond if, prior to such an act, the robot said: "Please don't turn me off, I don't want to die." Edinburgh, UK

I was very surprised to read in your editorial that nuclear fission reactors are accepted as one of the energy providers that should feature in the UK's energy generation portfolio (9 November, p 3) . As has been pointed out before in your magazine, Germany has decided to abandon that approach. The case against nuclear …

In his look at a world without online anonymity, Chris Baraniuk considers the effect on behaviour towards another person, if the first person can remain anonymous (26 October, p 34) . I wonder what the behavioural effects would be if, every time someone wanted to record or view my email or phone data, my financial …

Hurrah for your look at the benefits of urban trees, so relevant to my own worries about the loss of city foliage (9 November, p 40) . At present, I am disturbed by plans to fell mature poplars on a stretch of the north bank of the river Avon in Bath in the UK to …

Having just got thoroughly soaked clearing leaves from a blocked drain, I find it hard to believe that trees planted in urban streets prevent flooding. Hindhead, Surrey, UK

Further to your look at how common "modern" diseases were in the past (9 November, p 36) . I showed some years ago that the age-specific prevalence rates of cancers that involve bone were of the same order of magnitude in the past as they are today. This finding is in line with the hypothesis …

While it is excellent that Alfred Russel Wallace is at last getting his due credit alongside Charles Darwin for his work on the theory of evolution (9 November, p 48) , could I make a plea for the same thing to happen to arboriculturist Patrick Matthew? Both Darwin and Wallace admitted that Matthew beat them …

Your coverage of the 21-second universal law of urination (26 October, p 18) reminds me it has been common knowledge on the British music scene for years. The garage act So Solid Crew in their 2001 hit 21 Seconds were in full agreement with the Georgia Institute of Technology in Atlanta. You get a real …