Turbine turmoil

OPINION LETTERS Printing peace From Adrian Bowyer The problem of 3D printers being used to print plastic guns is in the air again (6 October, p 22), with my own RepRap printer mentioned as one potential route. As the article points out, attempts to use the law to prevent this are unlikely to succeed. So let’s have something stronger. While most technologies bring more benefits than problems, explosives seem the obvious exception. They have limited beneficial uses in mining, quarrying and demolition, although we do have alternatives for each. However, the principal use is the opposite of beneficial – killing. What’s more, virtually every machine that we make for killing relies on explosives, including guns. Explosives contain organic molecules with a lot of energy locked up in their chemical bonds. In other words, they are an ideal potential food source for yeasts, bacteria and archaea. But explosives haven’t been around long enough for explosive-eating microbes to evolve. Surely we could selectively breed such microbes – recombinant DNA techniques

would probably not be needed – and release them into the wild? Then bombs might rot in their silos and ammunition might turn to harmless waste. Priston, Somerset, UK

Turbine turmoil From Kay Siddell There is room for disagreement about the effects of wind turbines upon humans without casting those of us who suffer as wildeyed hysterics (6 October, p 26). I should dearly love to become a turbine refugee, but the 52 turbines in front of my house, the nearest being only 680 metres away, and more proposed behind it, mean that nobody is rushing to buy the property. Oddly enough I find the constant movement of the blades more disturbing than the noise. As the windows of every major room in the house look out onto the turbines, the curtains are kept drawn and as a result I have to take vitamin D tablets to make up for the lack of sunshine. Old Dailly, South Ayrshire, UK From David Allen Beauty may be in the eye of the beholder, but I think wind turbines are the most beautiful

Enigma Number 1721

Odds and evens SUSAN DENHAM To the right is a long multiplication sum in which odd digits have been replaced by O and even digits by E. What are the two three-figure numbers being multiplied?

O E O E E O O E

E O E O O O

O E E E E E

E O × E E E E

WIN £15 will be awarded to the sender of the first correct answer opened on Wednesday 28 November. The Editor’s decision is final. Please send entries to Enigma 1721, New Scientist, Lacon House, 84 Theobald’s Road, London WC1X 8NS, or to [email protected] (please include your postal address). Answer to 1715 Open the box: The piece of card was 8 cm by 3 cm The winner Peter Hayes of Moreland, Victoria, Australia

28 | NewScientist | 27 October 2012

things because they signify that there is a chance, a very slight chance, that my grandson has a future to look forward to. I have little sympathy for those whose event horizon is selfishly limited to how they feel, when the whole reason for wind farms is to get rid of the carbon emissions that may potentially bring down our civilisation. Fulham, South Australia

Human factor From Ken Pettett Of the 10 most influential popular science books that were chosen as a result of your readers’ poll (29 September, p 48), only one is about physics – A Brief History of Time by Stephen Hawking – and only one is about mathematics – Chaos by James Gleick. The other eight are all on biological themes, mainly to do with humanity. There are none on chemistry, engineering, astronomy (in the noncosmological sense), space travel, logic/philosophy, computing or technology. I know it’s risky to draw conclusions from a sample of just 4000 votes, but have we really become so introspective? I am filled with sadness and despair. Sandy, Bedfordshire, UK

Reality’s roundabout From Nathaniel Hellerstein It seems only logical for a circular definition to be the result of a search for the foundation of reality (29 September, p 34). The alternative is either an endless chain of explanations of explanations, or an explanation of reality in terms of something unreal. If reality is to have finite depth, then it must have a circular definition. Indeed, I would say that this circularity is the essence of reality. San Francisco, California, US

Aim for the stars From Babatunde Okunoye I was elated to read your interview with black American astrophysicist Hakeem Oluseyi, who recounted his journey from a tough childhood to his grand vision to democratise astronomy by putting telescopes in every country, including all the African nations (29 September, p 26). What a story. It highlights the fact that everyone can dream big and achieve those dreams. Abuja, Nigeria

Life’s snapshots From Frank Fahy As part of your special report on memory, David Robson wrote: “When people find it hard to recall specific events from their past,

however, they feel overwhelmed by life’s challenges, which slowly pushes them into depression” (6 October, p 38). This suggests that it might be a good idea to keep a regular visual record of life’s more enjoyable experiences, something made easier by small digital cameras and the vast and growing data storage capacities. The only downside is that formats change so fast it might not be possible to recover one’s record in later life if depression strikes. King’s Somborne, Hampshire, UK The editor writes: n Some people, such as “lifeloggers”, already keep a daily