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Fooled in Blackpool?
The last word– SWEAT ON THE WING Do pigeons sweat? If not, why not?
● Only mammals have sweat glands – so no, pigeons do not sweat. Nor do mammals such as cats, whales and rodents, which have lost most or all of their eccrine sweat glands – the ones that we use in shedding heat – while birds never developed them. In sweat-free mammals the kidneys deal with the excretory functions of sweat, and flushing or panting is how they cool themselves down. As another example of evaporative cooling, an over-hot cat not only pants but also moistens its fur with saliva. Bird skins are dry. However, as birds, including pigeons, have body temperatures that are generally several degrees higher than those of mammals, they do not need the same capacity to lose heat. When they do need to lose heat, they can raise their down feathers to
“Bird skins are dry. When they need to lose heat , they can raise their down feathers” cool the skin by ventilation; to conserve heat they flatten them. Beyond this, panting through open beaks causes evaporative cooling: hence the Afrikaans expression: “So hot the crows are yawning” (So warm dat die kraaie gaap). Finally, on very hot days, many kinds of birds, including pigeons, enjoy a bath. Jon Richfield Somerset West, South Africa Questions and answers should be kept as concise as possible. We reserve the right to edit items for clarity and style. Please include a daytime telephone number and a fax if you have one. Questions should be restricted to scientific enquiries about everyday phenomena. The writers of all answers that are published will receive a cheque for £25 (or the US$ equivalent). Reed Business Information Ltd reserves all rights to reuse question and answer material submitted
● Storks, cormorants and vultures indulge in urohydrosis: they literally wet and thus cool themselves by urinating down their legs. As birds do not urinate and defecate separately, everything comes out together, which makes bird droppings very watery. The heat required to evaporate this liquid from the surfaces of the legs cools the blood, carried close to the surface of the legs by a network of veins. Before condemning these birds for their unappealing party trick, it is worth adding that bird droppings contain uric acid, making it an effective antiseptic – very useful for vultures that spend a lot of their time trampling over rotting carcasses. Mike Follows Willenhall, West Midlands, UK
Last Words past and present, plus a full list of unanswered questions, are available on New Scientist’s website at www.newscientist.com
experienced workers did the outer candy coating, in similar “cement mixers”, and the finished product was polished by tumbling the sweets in powdered beeswax, except for the black ones, for which petroleum jelly was used, apparently to avoid a whitish bloom.
“The finished candy coating was polished by tumbling the sweets in powdered beeswax” Significantly, this was not a conveyor-belt manufacturing process. Each worker controlled their own rate, taking anything from an hour to an hour and a half per batch, depending on experience. Peter Verney Hebden Bridge, West Yorkshire, UK
NO WRINKLES How do they get the smooth, round chocolate coating on confectionery like Maltesers and Whoppers?
● I spent six months making Smarties, a similar type of confectionery, in 1977. The chocolate centres were tumbled in a device resembling a cement mixer that gave them repeated coatings alternating between sweet starchy liquid and powdered sugar, blowdried after each coat. It took a week or two to learn the knack of ensuring an even coating: we had to remove clumped material, get the right combination of wet and dry, and keep the layers thin. Trainees’ lumpy sweets were sold off cheap. I handled about a tonne of chocolate centres a day, putting on the white inner coat. More by readers in any medium or format. Send questions and answers to The Last Word, New Scientist, Lacon House, 84 Theobald’s Road, London WC1X 8NS, UK (fax +44 (0) 20 7611 1280) or by email to [email protected] (all correspondents should include their postal address in order to receive payment for answers). If you would like a complete list of all unanswered questions please send an SAE to LWQlist at the above address.
Memorable answer? The Last Word and New Scientist have teamed up with Crucial Technology (www.crucial.com/uk) and will be awarding each successful author a 512MB Gizmo! overdrive.
THIS WEEK’S QUESTIONS Part-time curdling On 3 July last year I opened a 2-litre plastic bottle of semi-skimmed, homogenised milk, with a use-by date of 5 July. I poured out a small cup of what turned out to be curds: a sniff confirmed the milk was off. I guessed that it had been inadequately refrigerated but because I was making pancakes I continued to pour it out, suspecting the sour taste would not be noticed. To my surprise, the remainder was fine and still was a day later: the curdling was restricted to the top 4 centimetres of the milk, where the bottle was fairly narrow. How can this have happened? Bob Ladd Edinburgh, UK
The day the world stopped How much force would be required to stop the world spinning? If you used, for example, the engines of the space shuttle to do it, how long would it take? And what would be the effect on the planet, in particular the weather and the tides? Stephen Frost Richmond, Surrey, UK The Aurora Electrical Company If electricity can be generated by moving a coil through a magnetic field, why do we not launch large coils into orbit? As they circled Earth within the planet’s magnetic field, the energy could be sent down from the coils via microwave: even people in remote areas could receive it. I suspect that this system would cost much less than energy generation does at present. So tell me, what flaws in this scheme would prevent me from picking up my Nobel prize? Robert Burns London, UK Growth potential My new shower gel proclaims: “New! Stimulates skin flora”. Is there any benefit in this? Peter Eaton Porto, Portugal Fooled in Blackpool? From the top of Blackpool Tower (approximately 150 metres) on the UK’s west coast, can you see the curvature of Earth along the Irish Sea horizon? I thought I could, but my friend disagreed. If I’m wrong, how high would we have needed to be? Mark Ford Bolton, Lancashire, UK
WHY DON’T PENGUINS’ FEET FREEZE? The latest collection from The Last Word, answering some of the world’s most baffling questions Available in bookstores and online at www.newscientist.com/lastword3.ns
● Only mammals have sweat glands – so no, pigeons do not sweat. Nor do mammals such as cats, whales and rodents, which have lost most or all of their eccrine sweat glands – the ones that we use in shedding heat – while birds never developed them. In sweat-free mammals the kidneys deal with the excretory functions of sweat, and flushing or panting is how they cool themselves down. As another example of evaporative cooling, an over-hot cat not only pants but also moistens its fur with saliva. Bird skins are dry. However, as birds, including pigeons, have body temperatures that are generally several degrees higher than those of mammals, they do not need the same capacity to lose heat. When they do need to lose heat, they can raise their down feathers to
“Bird skins are dry. When they need to lose heat , they can raise their down feathers” cool the skin by ventilation; to conserve heat they flatten them. Beyond this, panting through open beaks causes evaporative cooling: hence the Afrikaans expression: “So hot the crows are yawning” (So warm dat die kraaie gaap). Finally, on very hot days, many kinds of birds, including pigeons, enjoy a bath. Jon Richfield Somerset West, South Africa Questions and answers should be kept as concise as possible. We reserve the right to edit items for clarity and style. Please include a daytime telephone number and a fax if you have one. Questions should be restricted to scientific enquiries about everyday phenomena. The writers of all answers that are published will receive a cheque for £25 (or the US$ equivalent). Reed Business Information Ltd reserves all rights to reuse question and answer material submitted
● Storks, cormorants and vultures indulge in urohydrosis: they literally wet and thus cool themselves by urinating down their legs. As birds do not urinate and defecate separately, everything comes out together, which makes bird droppings very watery. The heat required to evaporate this liquid from the surfaces of the legs cools the blood, carried close to the surface of the legs by a network of veins. Before condemning these birds for their unappealing party trick, it is worth adding that bird droppings contain uric acid, making it an effective antiseptic – very useful for vultures that spend a lot of their time trampling over rotting carcasses. Mike Follows Willenhall, West Midlands, UK
Last Words past and present, plus a full list of unanswered questions, are available on New Scientist’s website at www.newscientist.com
experienced workers did the outer candy coating, in similar “cement mixers”, and the finished product was polished by tumbling the sweets in powdered beeswax, except for the black ones, for which petroleum jelly was used, apparently to avoid a whitish bloom.
“The finished candy coating was polished by tumbling the sweets in powdered beeswax” Significantly, this was not a conveyor-belt manufacturing process. Each worker controlled their own rate, taking anything from an hour to an hour and a half per batch, depending on experience. Peter Verney Hebden Bridge, West Yorkshire, UK
NO WRINKLES How do they get the smooth, round chocolate coating on confectionery like Maltesers and Whoppers?
● I spent six months making Smarties, a similar type of confectionery, in 1977. The chocolate centres were tumbled in a device resembling a cement mixer that gave them repeated coatings alternating between sweet starchy liquid and powdered sugar, blowdried after each coat. It took a week or two to learn the knack of ensuring an even coating: we had to remove clumped material, get the right combination of wet and dry, and keep the layers thin. Trainees’ lumpy sweets were sold off cheap. I handled about a tonne of chocolate centres a day, putting on the white inner coat. More by readers in any medium or format. Send questions and answers to The Last Word, New Scientist, Lacon House, 84 Theobald’s Road, London WC1X 8NS, UK (fax +44 (0) 20 7611 1280) or by email to [email protected] (all correspondents should include their postal address in order to receive payment for answers). If you would like a complete list of all unanswered questions please send an SAE to LWQlist at the above address.
Memorable answer? The Last Word and New Scientist have teamed up with Crucial Technology (www.crucial.com/uk) and will be awarding each successful author a 512MB Gizmo! overdrive.
THIS WEEK’S QUESTIONS Part-time curdling On 3 July last year I opened a 2-litre plastic bottle of semi-skimmed, homogenised milk, with a use-by date of 5 July. I poured out a small cup of what turned out to be curds: a sniff confirmed the milk was off. I guessed that it had been inadequately refrigerated but because I was making pancakes I continued to pour it out, suspecting the sour taste would not be noticed. To my surprise, the remainder was fine and still was a day later: the curdling was restricted to the top 4 centimetres of the milk, where the bottle was fairly narrow. How can this have happened? Bob Ladd Edinburgh, UK
The day the world stopped How much force would be required to stop the world spinning? If you used, for example, the engines of the space shuttle to do it, how long would it take? And what would be the effect on the planet, in particular the weather and the tides? Stephen Frost Richmond, Surrey, UK The Aurora Electrical Company If electricity can be generated by moving a coil through a magnetic field, why do we not launch large coils into orbit? As they circled Earth within the planet’s magnetic field, the energy could be sent down from the coils via microwave: even people in remote areas could receive it. I suspect that this system would cost much less than energy generation does at present. So tell me, what flaws in this scheme would prevent me from picking up my Nobel prize? Robert Burns London, UK Growth potential My new shower gel proclaims: “New! Stimulates skin flora”. Is there any benefit in this? Peter Eaton Porto, Portugal Fooled in Blackpool? From the top of Blackpool Tower (approximately 150 metres) on the UK’s west coast, can you see the curvature of Earth along the Irish Sea horizon? I thought I could, but my friend disagreed. If I’m wrong, how high would we have needed to be? Mark Ford Bolton, Lancashire, UK
WHY DON’T PENGUINS’ FEET FREEZE? The latest collection from The Last Word, answering some of the world’s most baffling questions Available in bookstores and online at www.newscientist.com/lastword3.ns