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“carefree sex” (22 November 2008, p 41 and p 5). Detractors will no doubt include those who are also against vaccinating girls against cervical cancer, just because in order to get it you have to have had sex at some point. Those who criticise the use of the PrEP pill on such grounds, and those in favour of abstinenceuntil-marriage campaigns, should consider the fact that in Africa and other parts of the world huge numbers of married women are contracting HIV. This is in large part due to their low social and economic status, allowing them little power to insist that their husband wears a condom even if they know or suspect he is HIVpositive, and even if they know he visits local prostitutes. Unmarried women also often face violence and force if they ask for condom use or refuse sex. This pill, if provided cheaply, could be a lifeline to millions of women, their children, and men. It is an opportunity that must be embraced. London, UK
From Marsha Rosengarten, Department of Sociology, Goldsmiths, University of London Though you covered many of the key issues raised with the promise of HIV pre-exposure prophylaxis (PrEP), enthusiasm for the possibility of reducing new infections appears to have glossed over the complexities of this intervention. The most appealing feature of PrEP is that it offers women who are unable to institute the use of condoms a form of possible protection. But on the basis of experience with the contraceptive pill, we can anticipate that PrEP will affect gender relations: while it will enhance some women’s capacity to protect themselves, it may place more onus for HIV prevention on them. Implementation of PrEP could merely replace some of the risk of HIV infection in otherwise healthy women with the risk of side effects from the drug – including risk in pregnancy. PrEP presents us with a quandary, one that will require advanced techniques for managing the coming together of a complex mix of biomedical and social factors. London, UK
Principles first From Sebastian Hayes Mark Buchanan’s report of the claim by Mitchell Feigenbaum and Vittorio Gorini that the celebrated space-time anomalies
of Special Relativity “emerge… from basic, purely mathematical considerations” shows how once-discredited “a priori” reasoning is becoming somewhat acceptable in science again (1 November 2008, p 28). The philosopher Gottfried Leibnitz took a broadly “rationalist” position, which essentially claims that certain truths about the universe can be deduced by reasoning alone. Isaac Newton, who also invented calculus at the same time, claimed to take an empiricist position: “I do not make hypotheses,” he famously wrote in 1713 concerning the nature of gravity. During the 20th century, largely because of the crushing weight of the positivist position in philosophy, a priori reasoning became thoroughly unrespectable in science. The work by Feigenbaum and Gorini and colleagues is a real body blow to that positivist scientific correctness. Shaftesbury, Dorset, UK
No. 1526 Bob Walker JOE did not trust the accuracy of his two digital thermometers, but he knew he could be confident that their percentage errors were constant over the range he needed to use them. He placed the sensors of both www.newscientist.com
thermometers in a beaker of oil and noted the temperatures indicated as the oil slowly warmed up. When one indicated 76.3 °C the other indicated 150.1 °F, and when one indicated 98.1 °C, the other indicated 184.3 °F. As the oil cooled down, one indicated temperature was 167.2 °F and Joe found he was able to calculate the corresponding true temperature of the oil in degrees celsius. What was the true temperature?
Earth was flat, 5000 years old and at the centre of the universe. It took scientists with a lot of guts to stand up and challenge those ideas. Hobart, Tasmania, Australia
For the record Testing the obvious From Jim Palfreyman Your correspondent Tony Kline implies that any human who has walked in the woods with a hungry Labrador that has dragged them towards a previously discovered food source will find the hypothesis that the animal has foresight obvious. He also says that “comparative psychologists
Enigma Degrees of error
should get out more and keep their eyes and minds open” (22 November 2008, p 25). This is an insult to the scientific process. Just because something is “obvious” doesn’t mean that it shouldn’t be tested. It was once “obvious” that the
£15 will be awarded to the sender of the first correct answer opened on 4 February. The Editor’s decision is final. Please send entries to Enigma 1526, New Scientist, 84 Theobald’s Road, London WC1X 8NS, or to enigma@ newscientist.com. The winner of Enigma 1520 is Peter Smith of Cropston, Leicester, UK. Answer to 1520 Just pondering 48 paving slabs make up the path
● We reported that the Wilkins Ice Shelf in Antarctica was “about the size of Scotland” (6 December 2008, p 7). In fact, the ice sheet used to cover about 16,000 square kilometres, and Scotland is actually almost five times that area. ● To refer, as we did, to a photovoltaic panel “rated to give 1 kilowatt per square metre in peak conditions… in the UK” (6 December 2008, p 30) was a tad over-optimistic. More realistically, it would take around 10 square metres of PV panel to generate 1 kilowatt. ● The half a million people expected to buy genetic tests in 2008 (22 November 2008, p 7) is the American Society of Human Genetics’ estimate for the whole world, not the US alone. Letters should be sent to: Letters to the Editor, New Scientist, 84 Theobald’s Road, London WC1X 8NS Fax: +44 (0) 20 7611 1280 Email: [email protected] Include your full postal address and telephone number, and a reference (issue, page number, title) to articles. We reserve the right to edit letters. Reed Business Information reserves the right to use any submissions sent to the letters column of New Scientist magazine, in any other format.
3 January 2009 | NewScientist | 17
“carefree sex” (22 November 2008, p 41 and p 5). Detractors will no doubt include those who are also against vaccinating girls against cervical cancer, just because in order to get it you have to have had sex at some point. Those who criticise the use of the PrEP pill on such grounds, and those in favour of abstinenceuntil-marriage campaigns, should consider the fact that in Africa and other parts of the world huge numbers of married women are contracting HIV. This is in large part due to their low social and economic status, allowing them little power to insist that their husband wears a condom even if they know or suspect he is HIVpositive, and even if they know he visits local prostitutes. Unmarried women also often face violence and force if they ask for condom use or refuse sex. This pill, if provided cheaply, could be a lifeline to millions of women, their children, and men. It is an opportunity that must be embraced. London, UK
From Marsha Rosengarten, Department of Sociology, Goldsmiths, University of London Though you covered many of the key issues raised with the promise of HIV pre-exposure prophylaxis (PrEP), enthusiasm for the possibility of reducing new infections appears to have glossed over the complexities of this intervention. The most appealing feature of PrEP is that it offers women who are unable to institute the use of condoms a form of possible protection. But on the basis of experience with the contraceptive pill, we can anticipate that PrEP will affect gender relations: while it will enhance some women’s capacity to protect themselves, it may place more onus for HIV prevention on them. Implementation of PrEP could merely replace some of the risk of HIV infection in otherwise healthy women with the risk of side effects from the drug – including risk in pregnancy. PrEP presents us with a quandary, one that will require advanced techniques for managing the coming together of a complex mix of biomedical and social factors. London, UK
Principles first From Sebastian Hayes Mark Buchanan’s report of the claim by Mitchell Feigenbaum and Vittorio Gorini that the celebrated space-time anomalies
of Special Relativity “emerge… from basic, purely mathematical considerations” shows how once-discredited “a priori” reasoning is becoming somewhat acceptable in science again (1 November 2008, p 28). The philosopher Gottfried Leibnitz took a broadly “rationalist” position, which essentially claims that certain truths about the universe can be deduced by reasoning alone. Isaac Newton, who also invented calculus at the same time, claimed to take an empiricist position: “I do not make hypotheses,” he famously wrote in 1713 concerning the nature of gravity. During the 20th century, largely because of the crushing weight of the positivist position in philosophy, a priori reasoning became thoroughly unrespectable in science. The work by Feigenbaum and Gorini and colleagues is a real body blow to that positivist scientific correctness. Shaftesbury, Dorset, UK
No. 1526 Bob Walker JOE did not trust the accuracy of his two digital thermometers, but he knew he could be confident that their percentage errors were constant over the range he needed to use them. He placed the sensors of both www.newscientist.com
thermometers in a beaker of oil and noted the temperatures indicated as the oil slowly warmed up. When one indicated 76.3 °C the other indicated 150.1 °F, and when one indicated 98.1 °C, the other indicated 184.3 °F. As the oil cooled down, one indicated temperature was 167.2 °F and Joe found he was able to calculate the corresponding true temperature of the oil in degrees celsius. What was the true temperature?
Earth was flat, 5000 years old and at the centre of the universe. It took scientists with a lot of guts to stand up and challenge those ideas. Hobart, Tasmania, Australia
For the record Testing the obvious From Jim Palfreyman Your correspondent Tony Kline implies that any human who has walked in the woods with a hungry Labrador that has dragged them towards a previously discovered food source will find the hypothesis that the animal has foresight obvious. He also says that “comparative psychologists
Enigma Degrees of error
should get out more and keep their eyes and minds open” (22 November 2008, p 25). This is an insult to the scientific process. Just because something is “obvious” doesn’t mean that it shouldn’t be tested. It was once “obvious” that the
£15 will be awarded to the sender of the first correct answer opened on 4 February. The Editor’s decision is final. Please send entries to Enigma 1526, New Scientist, 84 Theobald’s Road, London WC1X 8NS, or to enigma@ newscientist.com. The winner of Enigma 1520 is Peter Smith of Cropston, Leicester, UK. Answer to 1520 Just pondering 48 paving slabs make up the path
● We reported that the Wilkins Ice Shelf in Antarctica was “about the size of Scotland” (6 December 2008, p 7). In fact, the ice sheet used to cover about 16,000 square kilometres, and Scotland is actually almost five times that area. ● To refer, as we did, to a photovoltaic panel “rated to give 1 kilowatt per square metre in peak conditions… in the UK” (6 December 2008, p 30) was a tad over-optimistic. More realistically, it would take around 10 square metres of PV panel to generate 1 kilowatt. ● The half a million people expected to buy genetic tests in 2008 (22 November 2008, p 7) is the American Society of Human Genetics’ estimate for the whole world, not the US alone. Letters should be sent to: Letters to the Editor, New Scientist, 84 Theobald’s Road, London WC1X 8NS Fax: +44 (0) 20 7611 1280 Email: [email protected] Include your full postal address and telephone number, and a reference (issue, page number, title) to articles. We reserve the right to edit letters. Reed Business Information reserves the right to use any submissions sent to the letters column of New Scientist magazine, in any other format.
3 January 2009 | NewScientist | 17