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Ice sums
The last word– COLOUR OF CUSTARD Why is custard powder pink until you add the liquid, upon which it becomes yellow?
● Custard powder is often coloured with a blend of tartrazine yellow or quinoline yellow food dyes, mixed with sunset yellow. In solution with water, these colours are true to their names, but in their pre-dissolved solid phase the sunset yellow portion is more orange-red, and this colour tends to dominate. When mixed with the other custard powder components, which are white, the result is a pastel orange-red, or pink. Many pure colourants, both dyes and pigments, have a very different shade from that required in their final state. Dave Holey Lower Hutt, New Zealand
same when the glaciers are gone, why shouldn’t the rivers still receive the same amount of water?
● The water in a river does not depend only on the amount of water that falls as rain in a year, but also on when and how much. Generally, glacier-fed rivers will receive a constant trickle from melting ice in the winter and, as the temperature rises in spring, the amount of water in the river increases. If the glaciers disappear, there will be no slowly melting ice, so the glaciers’ regulation of the water flow will cease. Any rain that falls will instead reach the river rapidly, while in dry spells there will be no water at all. So, instead of having a river all
year round with a flow rate that is strongly linked to temperature, you will have a much lower water level most of the time with higher levels after rain. The average level over the year will indeed stay the same, but in extreme cases it could mean the difference between a constant flow and a dry river bed with occasional flash floods. That compares the case of no glaciers with the case of constant glaciers. In reality, glaciers have been losing mass since the end of the last ice age. Once all the ice has melted there really will be less river water available, so the average level will be lower and more erratic. Rick Didcot, Oxfordshire, UK
● Glaciers act as reservoirs that even out the flow of water so that a given year’s precipitation takes generations to reach the sea. Without glaciers to regulate the flow, a rainy season’s precipitation – potentially all of that year’s rain – could flood down within months, leaving devastation and eroded canyons for the rest of the year. The glaciers’ buffering effect is huge. Jon Richfield Somerset West, South Africa
THIS WEEK’S QUESTIONS Leaf antlers What causes these strange horny growths on tree leaves (see Photo)? Mike Child Bedford, UK Save our cars On the south coast of New Zealand, the steelwork of our cars is constantly being corroded. Why can’t cars be protected by connecting a sacrificial anode made of zinc to the body and chassis in the same way as steel ships? Pete Fowler Tuatapere, New Zealand
ICE SUMS New Scientist has reported that rivers in the Himalayas will be starved of water when the glaciers disappear. If the glaciers were neither shrinking nor growing, the
Plant depression When I was growing up in Luanda, Angola, I remember a peculiar bush. When you touched it, the area where contact was made wilted immediately, with all the leaves on that branch drooping. This lasted for only 2 or 3 minutes, after which the leaves slowly became erect and returned to normal. Does anyone know the name of this bush and why it behaves in this way? Luis M. Luis Virginia, US
“Any rain that falls will reach the river rapidly, while in dry spells there will be no water at all” amount of water fed into the rivers from the glaciers should be roughly equal to precipitation in the Himalayas over the same period. Assuming that rainfall remains the
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 email address if you have one. Questions should be restricted to scientific enquiries about everyday phenomena. The writers of all published answers will receive a cheque for £25 (or the US$ equivalent). Reed Business Information Ltd reserves all rights to reuse question and answer material submitted by
Last Words past and present, plus a full list of unanswered questions, are available at www.newscientist.com/lastword
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), by email to [email protected] or visit www. newscientist.com/lastword.ns (please include a postal address in order to receive payment for answers). If you would like a 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.
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
● Custard powder is often coloured with a blend of tartrazine yellow or quinoline yellow food dyes, mixed with sunset yellow. In solution with water, these colours are true to their names, but in their pre-dissolved solid phase the sunset yellow portion is more orange-red, and this colour tends to dominate. When mixed with the other custard powder components, which are white, the result is a pastel orange-red, or pink. Many pure colourants, both dyes and pigments, have a very different shade from that required in their final state. Dave Holey Lower Hutt, New Zealand
same when the glaciers are gone, why shouldn’t the rivers still receive the same amount of water?
● The water in a river does not depend only on the amount of water that falls as rain in a year, but also on when and how much. Generally, glacier-fed rivers will receive a constant trickle from melting ice in the winter and, as the temperature rises in spring, the amount of water in the river increases. If the glaciers disappear, there will be no slowly melting ice, so the glaciers’ regulation of the water flow will cease. Any rain that falls will instead reach the river rapidly, while in dry spells there will be no water at all. So, instead of having a river all
year round with a flow rate that is strongly linked to temperature, you will have a much lower water level most of the time with higher levels after rain. The average level over the year will indeed stay the same, but in extreme cases it could mean the difference between a constant flow and a dry river bed with occasional flash floods. That compares the case of no glaciers with the case of constant glaciers. In reality, glaciers have been losing mass since the end of the last ice age. Once all the ice has melted there really will be less river water available, so the average level will be lower and more erratic. Rick Didcot, Oxfordshire, UK
● Glaciers act as reservoirs that even out the flow of water so that a given year’s precipitation takes generations to reach the sea. Without glaciers to regulate the flow, a rainy season’s precipitation – potentially all of that year’s rain – could flood down within months, leaving devastation and eroded canyons for the rest of the year. The glaciers’ buffering effect is huge. Jon Richfield Somerset West, South Africa
THIS WEEK’S QUESTIONS Leaf antlers What causes these strange horny growths on tree leaves (see Photo)? Mike Child Bedford, UK Save our cars On the south coast of New Zealand, the steelwork of our cars is constantly being corroded. Why can’t cars be protected by connecting a sacrificial anode made of zinc to the body and chassis in the same way as steel ships? Pete Fowler Tuatapere, New Zealand
ICE SUMS New Scientist has reported that rivers in the Himalayas will be starved of water when the glaciers disappear. If the glaciers were neither shrinking nor growing, the
Plant depression When I was growing up in Luanda, Angola, I remember a peculiar bush. When you touched it, the area where contact was made wilted immediately, with all the leaves on that branch drooping. This lasted for only 2 or 3 minutes, after which the leaves slowly became erect and returned to normal. Does anyone know the name of this bush and why it behaves in this way? Luis M. Luis Virginia, US
“Any rain that falls will reach the river rapidly, while in dry spells there will be no water at all” amount of water fed into the rivers from the glaciers should be roughly equal to precipitation in the Himalayas over the same period. Assuming that rainfall remains the
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 email address if you have one. Questions should be restricted to scientific enquiries about everyday phenomena. The writers of all published answers will receive a cheque for £25 (or the US$ equivalent). Reed Business Information Ltd reserves all rights to reuse question and answer material submitted by
Last Words past and present, plus a full list of unanswered questions, are available at www.newscientist.com/lastword
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), by email to [email protected] or visit www. newscientist.com/lastword.ns (please include a postal address in order to receive payment for answers). If you would like a 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.
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