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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. THE LAST WORD I’m not tired As babies, both my children fought sleep, getting so overtired and fractious that they would hardly take milk at feeds. Why do some babies insist on trying to stay awake? n After raising three children and consulting with thousands of mothers of infants, my suggestion to parents of such children is simple: they must use their own insight about what they know about their own child to figure out what to do, rather than following any of the millions of advice books. Kids have trouble falling asleep for the same reasons as adults, including the need for comfort in the arms of a parent, alarm and anxiety, hunger, pain, not feeling sleepy, and more. What to do so everyone in the home gets enough sleep may be more complex, and there is never just one solution. For children under 2, who are developmentally only capable of attaching through the senses to their primary caregiver, the need for physical and emotional closeness with their parents is pre-eminent and requires frequent refuelling. If they have experienced more separation – including while asleep – from their parents than they can manage, then they will resist sleep until the need is met. Similarly, many adults cannot sleep when their partner is away. Just because society now says our kids should be independent of us does not mean their brains are equipped to cope with it. “Sleep training” techniques for babies may be shown to work in the short term but could have serious negative consequences for child-parent relationships in the long term, according to my colleague Gordon Neufeld of the Neufeld Institute in Winnipeg, Canada, which researches childhood. Elizabeth Hatherell Neufeld Institute Winnipeg, Canada n This refusal to attempt to sleep is something my sister’s eldest daughter persisted in until she was nearly 8 months old and was the cause of much discussion in my family. There were at least 10 of us including my father, who is a family doctor, so many points of view were aired. The idea that prevailed after more than a little reading around the subject was that this dislike – which is almost fear of sleep – in some young babies arises from a fear of releasing the conscious world. At a very young age, children often believe that when something is not visible and physically available, it no longer exists and never will. It is similar to the way in which a child screams for its mother or father or a favourite toy when they have only been out of the room for a few seconds. So the same could apply to sleep. A child does not want to sleep for fear that when it closes its eyes and relinquishes its hold on the world, none of the familiar comforting sights and sounds of its short life will be present. Until a child becomes used to the concept of the world having substance even though it is not currently visible, it will fear the loss of consciousness. Our secondary theory was the idea that some children just don’t want to sleep, because they will lose valuable playing, eating and general mess-making time. Frederick White Ashford, Kent, UK Unmusical scale My kettle becomes very noisy when it boils. I live in a hard-water area, so I regularly treat it to remove the build-up of limescale. For a few days it then seems much smoother and quieter. What’s going on? n I assume you refer to simmering, the noisy stage of hissing or “singing” when water explosively forms steam bubbles against the heating element, but the surrounding water is cool enough to implode the bubbles quickly after they form. That cyclic process produces the sound, with the kettle body acting as a soundboard. If you are unsure that this is causing the noise, gently slosh the water in the kettle back and forth when the noise starts. If it really is simmering, sloshing interrupts the noise until the proper, comparatively quiet, boiling gets under way. In a clean kettle, heat passes efficiently through the heating surface, rapidly completing the simmering stage, so singing soon stops. Also, a clean, smooth heating surface retains bubbles poorly; they detach while small and implode in the water instead of causing large impacts against the heating surface, so the soundboard produces little sound. However, limescale is a poorer conductor than the heating element or kettle wall, and a thick mass of scale accumulates heat before passing it on. Accordingly the simmering starts slowly, but boiling starts even more slowly, so that the simmering lasts longer. Jon Richfield Somerset West, South Africa This week’s question BACK IN BLACK I was reading in very dim light last night and found that I could not read black text on a white background (the character size was about 8 point) but could read white on a black background. I’m 48 years old and have to wear reading glasses, which I did not have with me at the time. I expected not to be able to read black-on-white text, but was surprised I could read the opposite. Why is this? It seems counter-intuitive. Ben Deighton Halifax, West Yorkshire, UK “For children under 2, the need for physical and emotional closeness with parents is pre-eminent” Last words past and present, plus questions, at last-word.com A new collection: the usual insight, ingenuity and wit – this time with full colour photographs Available from booksellers and at newscientist.com/orangutans Why are orangutans orange?
