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Ice spy
THE LAST WORD
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Pass the port Why is gout worse at night?
n I am one of those unfortunate individuals who occasionally experience gout attacks. Having studied the problem for a long time I have realised that it is caused by consuming certain food and drinks. By thinking back to what I ate earlier, I can usually determine the cause. Green string beans, lima (butter) beans, celery, V8 vegetable juice, shellfish and sometimes a glass of wine, but not all wines, bring on an attack. Most of these will produce a mild ache followed by pain in my foot, toe or knee within 4 hours. But in the case of prawns or shrimp, the pain does not begin for about 8 hours. As these foods are not the sort of thing people eat at breakfast, but more for the evening meal, this means the onset of pain is usually in the evening hours. Fortunately, I have found that a 25-milligram tablet of indometacin will begin to
“Green beans, lima beans, celery, shellfish and sometimes a glass of wine bring on gout attacks”
While indometacin is a common treatment for gout, many others are available. If you think you may have the symptoms of this condition, seek medical advice before taking any drug – Ed
Ice spy When I put ice into my whisky I see lovely swirling patterns in the liquid. These are obviously to do with temperature and density differences between the melting ice and spirit. But what mechanism allows me to see these differences? What optical effects are at play?
alleviate the pain about 2 and a half hours after the first signs of a gout attack. That’s why I always keep a bottle of indometacin in my home or car and take it with me whenever I travel. J. Robert Wagner Plymouth Meeting, Pennsylvania, US
n What your correspondent sees is caused by the mixing of liquids at different densities, but it can only be observed thanks to the refraction of light. Light travels in a straight line through a vacuum and through a
Questions and answers should be concise. We reserve the right to edit items for clarity and style. Include a daytime telephone number and email address if you have one. Restrict questions to scientific enquiries about everyday phenomena. The writers of published answers will receive a cheque for £25 (or US$ equivalent). Reed Business Information Ltd reserves all rights to reuse question and answer material submitted by readers in any medium or format.
New Scientist retains total editorial control over the content of The Last Word. Send questions and answers to The Last Word, New Scientist, Lacon House, 84 Theobald’s Road, London WC1X 8NS, UK, by email to [email protected] or visit www.last-word.com (please include a postal address in order to receive payment for answers). For a list of all unanswered questions send an SAE to LWQlist at the above address.
medium of uniform density. When light moves from one medium to another, its path changes direction by an amount that depends on the difference in density of the two media. The angle is calculated using Snell’s law. When light passes through a liquid of variable density, its path will change continually. This dynamic refraction results in an attractive shimmer effect. To maximise this effect, allow your glass of spirit (or warm water for abstainers) to sit a few minutes so the liquid is perfectly still. Hold the glass to a bright window and gently put in an ice cube. You will see the ice melt and the cold, dense water flow around the ice in a laminar way. The flow then becomes turbulent as it moves down and mixes with the less dense liquid below. The shimmering dynamic refraction allows you to see and appreciate
the beauty of the flow patterns and the chaotic mixing. An upside-down negative of this phenomenon can be seen if you hold the flame of a candle or cigarette lighter in front of a projector while it is shining white light onto a screen. The invisible convection currents created by hot, less-dense air rising and mixing with the denser air of the room can be inferred from the shadows cast on the screen. Don’t use a match because the mesmeric effect of the moving shadows may cause you to burn your fingers. In a still room, the shadows from the convection current can be up to a hundred times the size of the flame. Such dynamic refraction can also be seen in the heat haze above sunsoaked roads and above radiators by sunlit windows. Dynamic refraction and its associated scintillation have even been immortalised in a nursery rhyme: Twinkle, Twinkle, Little Star. David Muir Science department Portobello High School Edinburgh, UK
This week’s question Tough customer
On holiday in Tuscany, Italy, in August, I saw this creeping across the road (see photo). It is about a thumb’s length, with dry, tough skin and no legs, and it moves a bit like a leech or a caterpillar. What is it? What does it eat? Mark Barrett London, UK
Will we ever speak dolphin? The new book out now: packed full of wit, knowledge and extraordinary discovery Available from booksellers and at newscientist.com/dolphins
Last words past and present, plus questions, at last-word.com
Pass the port Why is gout worse at night?
n I am one of those unfortunate individuals who occasionally experience gout attacks. Having studied the problem for a long time I have realised that it is caused by consuming certain food and drinks. By thinking back to what I ate earlier, I can usually determine the cause. Green string beans, lima (butter) beans, celery, V8 vegetable juice, shellfish and sometimes a glass of wine, but not all wines, bring on an attack. Most of these will produce a mild ache followed by pain in my foot, toe or knee within 4 hours. But in the case of prawns or shrimp, the pain does not begin for about 8 hours. As these foods are not the sort of thing people eat at breakfast, but more for the evening meal, this means the onset of pain is usually in the evening hours. Fortunately, I have found that a 25-milligram tablet of indometacin will begin to
“Green beans, lima beans, celery, shellfish and sometimes a glass of wine bring on gout attacks”
While indometacin is a common treatment for gout, many others are available. If you think you may have the symptoms of this condition, seek medical advice before taking any drug – Ed
Ice spy When I put ice into my whisky I see lovely swirling patterns in the liquid. These are obviously to do with temperature and density differences between the melting ice and spirit. But what mechanism allows me to see these differences? What optical effects are at play?
alleviate the pain about 2 and a half hours after the first signs of a gout attack. That’s why I always keep a bottle of indometacin in my home or car and take it with me whenever I travel. J. Robert Wagner Plymouth Meeting, Pennsylvania, US
n What your correspondent sees is caused by the mixing of liquids at different densities, but it can only be observed thanks to the refraction of light. Light travels in a straight line through a vacuum and through a
Questions and answers should be concise. We reserve the right to edit items for clarity and style. Include a daytime telephone number and email address if you have one. Restrict questions to scientific enquiries about everyday phenomena. The writers of published answers will receive a cheque for £25 (or US$ equivalent). Reed Business Information Ltd reserves all rights to reuse question and answer material submitted by readers in any medium or format.
New Scientist retains total editorial control over the content of The Last Word. Send questions and answers to The Last Word, New Scientist, Lacon House, 84 Theobald’s Road, London WC1X 8NS, UK, by email to [email protected] or visit www.last-word.com (please include a postal address in order to receive payment for answers). For a list of all unanswered questions send an SAE to LWQlist at the above address.
medium of uniform density. When light moves from one medium to another, its path changes direction by an amount that depends on the difference in density of the two media. The angle is calculated using Snell’s law. When light passes through a liquid of variable density, its path will change continually. This dynamic refraction results in an attractive shimmer effect. To maximise this effect, allow your glass of spirit (or warm water for abstainers) to sit a few minutes so the liquid is perfectly still. Hold the glass to a bright window and gently put in an ice cube. You will see the ice melt and the cold, dense water flow around the ice in a laminar way. The flow then becomes turbulent as it moves down and mixes with the less dense liquid below. The shimmering dynamic refraction allows you to see and appreciate
the beauty of the flow patterns and the chaotic mixing. An upside-down negative of this phenomenon can be seen if you hold the flame of a candle or cigarette lighter in front of a projector while it is shining white light onto a screen. The invisible convection currents created by hot, less-dense air rising and mixing with the denser air of the room can be inferred from the shadows cast on the screen. Don’t use a match because the mesmeric effect of the moving shadows may cause you to burn your fingers. In a still room, the shadows from the convection current can be up to a hundred times the size of the flame. Such dynamic refraction can also be seen in the heat haze above sunsoaked roads and above radiators by sunlit windows. Dynamic refraction and its associated scintillation have even been immortalised in a nursery rhyme: Twinkle, Twinkle, Little Star. David Muir Science department Portobello High School Edinburgh, UK
This week’s question Tough customer
On holiday in Tuscany, Italy, in August, I saw this creeping across the road (see photo). It is about a thumb’s length, with dry, tough skin and no legs, and it moves a bit like a leech or a caterpillar. What is it? What does it eat? Mark Barrett London, UK
Will we ever speak dolphin? The new book out now: packed full of wit, knowledge and extraordinary discovery Available from booksellers and at newscientist.com/dolphins