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LID SCALES CYLINDRICAL HOLE LOAD SENSOR 50 mm 15 mm PLASTIC FOOT RUBBER PAD BOX 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 them to twist and rub against the sides of the hole. As my full weight bore down, friction with the floor would prevent the plastic foot from recentralising. Instead it remained in contact with the sides of the hole, affecting the reading. My solution was to put the scales in a wooden box as shown. The base of the box had to be thick enough – 15 millimetres proved sufficient – not to bend when I stood on it, and large enough for the scales not to touch the sides. I added a lid (which obviously needs to be removed before using the scales) to keep out dust, spiders and so on. Anyone building such a box should ideally glue the rubber pads to the base to prevent the scales sliding into the sides of the box. Thus equipped, the scales will give reproducible readings whatever the floor type. Brian Longson Dorchester, Dorset, UK This week’s questions BASS INSTINCTS I am a tenor/countertenor singer with a normal range from G (first line, bass clef) to two Ds above middle C. When I had a sore throat for a few days I lost my upper notes but could easily sing great C, which is two octaves below middle C. Why does this happen? And why do I not retain these bass notes when my throat heals? I always wanted to be a basso profundo. Len Yaeger Minneapolis, Minnesota, US ROCK ON I read that an asteroid with a diameter somewhere between 8 and 18 metres passed within 12,000 kilometres of Earth on 27 June. To what extent would its course have been affected by this brush with the Earth’s gravitational field? Pedro Soler Menorca, Spain CRIME THRILLER Why do some people, myself included, get a thrill out of breaking the law even though we know perfectly well it is wrong? Jesse Geiger Elmira Correctional Facility Elmira, New York, US FEAR OF HEIGHT If I saw a huge dinosaur, I would probably run for my life. So why do ants seem oblivious to a human towering over them? Do ants not get scared? Robert Watson Jesmond, New South Wales, Australia MOON BLUES Last year I was watching the sun set in Crete, as it went through all shades of red in the final minutes. Then I glanced at the moon and saw it had turned blue. How was this possible, and is it the basis of the saying “once in a blue moon”? Patrick Casement London, UK EAR, EAR Is there any evolutionary advantage to having protruding ears? Do they help to synthesise vitamin D by catching more sunlight? Peter Slessenger Reading, Berkshire, UK Last words past and present, plus questions, at last-word.com The latest collection: witty, brilliant, intelligent and packed with insight Available from booksellers and at www.newscientist.com/elephants Why can’t elephants jump? Weighty concern Why does your weight seem to differ if your bathroom scales are placed on carpet instead of a solid wooden floor? n Bathroom scales operate on the principle that your weight compresses part of a mechanism, such as a spring. If the scales are sitting on a soft surface such as carpet, the surface acts as a spring in its own right. In this situation the reading will be lower than it should be, since your weight goes into compressing both the mechanism and the surface beneath. Being inflexible, a hard floor has a negligible effect on the reading. Neil Ayre Kalgoorlie, Western Australia n I found that my scales gave readings that were reproducible to within 100 grams – as advertised on the packaging – but only if consistently placed in the same position on a hard, level floor. Reproducibility declined if the floor was uneven. And with the scales on a carpet, its readings of my weight could vary by a couple of kilograms. The scales have load sensors in each of the four corners. Each sensor is glued to a plastic foot which sits within a cylindrical hole and rests on a rubber pad, as shown in the diagram above. I noticed that when stepping on the scales I always put some sideways force on the plastic feet, causing at least one of “Being inflexible, a hard floor has a negligible effect on the reading produced by the scales”
