Letters archive

The equation devised by Frank Drake to estimate the number of advanced civilisations in the Milky Way detectable by radio signals received another couple of airings last month. It was alluded to in your "Instant expert" on astrobiology ( 7 May ), and mentioned the following week in your editorial (14 May, p 3) . …

Twice in his interesting article on the limits of knowledge (7 May, p 34) , Michael Brooks stated that quantum uncertainty means the universe could have appeared from nothing – meaning that it could have arisen from a quantum vacuum. But a quantum vacuum is not nothing; it is a particular kind of fluctuating energy …

I'd like to add an observation consistent with Benjamin Libet's experiments, which showed volunteers' brains initiating movement before they became consciously aware of an intention to move, as mentioned in "The grand delusion" (14 May, p 35) . When rock climbing many years ago, I often found that while tackling a difficult move I would …

We read a great deal in New Scientist about the world food crisis, the threat of global shortages and food wastage, as in the article by UN Environment Programme director Achim Steiner (16 April, p 28) . One important but rarely mentioned factor is that a considerable proportion of the world's food is eaten by …

Soldiers playing video games that "desensitise players to violence" might be sleeping more easily (12 March, p 25) , but should the rest of us be? You don't have to be an expert to understand that the "more violent dreams combined with a sense of helplessness" experienced by those who didn't play the games, were …

You describe the use of computers that use evolution-like methods to create designs whose success cannot be fully understood, as part of "The next wave" (14 May, p 30) . Surely all that is being achieved is a tireless and very high-speed use of that usually derided technique, suck-it-and-see.

"The MIT puzzle" part of the "Killer codes" feature ( 21 May, p 40 ), mentioned that the RSA algorithm was developed by Ron Rivest, Adi Shamir and Len Adleman in 1977. In fact this algorithm had been worked out before then by mathematicians James Ellis and Clifford Cocks, but as they were working for …

The difference between the short and long-term carbon cycles seems to be overlooked in "The rush towards renewable oil" (21 May, p 6) . Planting tomatoes and trees or growing algae only "offsets" fossil-fuel carbon emissions until the tomato is eaten and respired, the tree dies and rots or the biofuel is burned; the carbon …

To describe your religion in 17 characters or less on the UK census form is a challenge (Letters, 23 April, p 28) . Alan Charlton made do with "ScientificRealist" (17 characters), since "scientific realist" (18), as suggested by earlier correspondent Martin Hunt, was too long. Thank the good Lord I live in California, so I …

Robots downloading apps to acquire new functionality (19 February, p 24) ? While the idea appeals to my inner nerd, I'm afraid it may appeal to other people's inner criminal. Imagine the day that malicious software could result in a robot letting strangers into your house, setting fires or even harvesting your organs while you …

Regarding the interview with dream researcher J. Allan Hobson (23 April, p 48) , I like to think of brain activity while asleep as akin to a computer defragmenting its hard drive. Dreams are just some of this information transfer rising to the conscious level as memories are relocated to more appropriate locations.

On the subject of the supposedly outmoded "air scribble" gesture used to request a restaurant bill (Feedback, 9 April) , the scribble is not completely redundant yet. Bills are still sometimes signed for when paid with a credit card. However, I still prefer my business partner's method: he gets the waiter's attention and then pretends …

The "Drive-by advertising" story (7 May, p 24) , which mentions safety fears about turning car windows into billboards, reminded me of a passage in an old sci-fi novel. The Space Merchants by Cyril M. Kornbluth and Frederik Pohl, published in 1953, describes a time when advertising companies dominate the world, and includes the quote: …

• In the feature on gut microbes (14 May, p 42) , the figure in the first paragraph was wrong. It should have said the bowel disease necrotising enterocolitis kills up to 5 per cent of premature babies. • The solution we published in the 7 May issue (p 30) to Enigma puzzle 1639 "Square …