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THE LAST WORD Weighty concern Why does your weight seem to differ if your bathroom scales are placed on carpet instead of a solid wooden floor? (Continued) n An earlier answer describing the carpet as an additional spring affecting the scales (16 July) seems to be rewriting Newton’s second law of motion. Essentially there are two springs in series – the scales, which contain springs, and the carpet, which is springy. If we ignore the weight of the scales, then each spring carries the same load. The carpet simply deforms more than a wooden floor in response to your weight. If we take the earlier respondent’s argument (that the surface acts as a spring in its own right, “soaking up” some of your weight and reducing the reading on the scales) to its extreme, then if the scales were placed on a very compliant surface, your weight would register as zero. But that doesn’t happen: at some point the carpet is compressed enough for the scales to register the person’s weight. Charlie Main Division of Electronic Engineering and Physics University of Dundee Angus, UK Fear of height If I saw a huge dinosaur, I would run for my life. So why do ants seem oblivious to a human towering over them? Do ants not get scared? n I think it’s all relative. I measured the height of several local ants and found the largest black carpenter ants reach an average of 5 millimetres above the ground. The tallest dinosaurs were about 8 metres high. Humans are mostly less than 2 metres tall. This would make the largest dinosaur about four times the height of an average human while the average human would be about 1000 times the size of an ant. Some ants do, in fact, seem to sense us – especially if our shadows fall over them – and run. But mostly I suspect we are just too big to enter their awareness. Also, I wonder if ants ever look up. Earle McNeil Olympia, Washington, US n Ants’ attitude to life is vastly different to that of mammals, which invest a great deal of time and energy in their young and have evolved numerous means of self-protection. Ants, on the other hand, invest very little in their myriad workers, all being easily replaceable clones, so they have no individual fear of being killed. If the nest is threatened, however, it’s a different story, and they will defend it to the death. Also, ants have been around for more than 100 million years. If they think about it at all, which is unlikely, no doubt ants would see humans as a very transient species, occupying but a moment in time on their planet. Tony Holkham Boncath, Pembrokeshire, UK Penalty tricks Is there anything science can tell us about taking a penalty kick? The goal in soccer is a lot bigger than the goalkeeper, so it should be easy to score, but so many penalty takers don’t. Is there a well-founded, foolproof way of taking fear, emotion and human error out of the equation and guaranteeing a goal? (Continued) n The notion, mentioned by an earlier correspondent (20 August), that the Italian soccer team used neurofeedback (consciously controlling bodily functions that normally operate subconsciously) to help win the 2006 World Cup does nothing to describe what their success was due to. To answer whether there is a foolproof way to guarantee scoring a goal, there clearly is not. The question does not account for the presence of the goalkeeper, who can make the target for the kicker much smaller if they guess correctly which side the kicker is aiming at. That makes for more errors in kicking, even when the kicker aims where the goalkeeper isn’t. However, game theory suggests that if the behaviour of either the kicker or goalkeeper is predictable, then an advantage can be gained – not a “guaranteed goal”, but an increase in the percentage of successful shots (or, indeed, successful saves). To prevent this advantage, the only solution is for both kicker and goalkeeper to choose a side at random – not easily done in the human brain. And goalkeepers may learn to read small movements made by some kickers. In order to be truly random, perhaps coaches could flip a coin and then send an order to the kicker, and do the same for the goalkeeper. In this case, the kicker needn’t try to kick to a spot that the goalkeeper can’t reach, it being understood that 50 per cent of kicks will likely be blocked and 50 per cent will get through. So much for the theory. Even if each game were totally random, there would still be a winner in a penalty shoot-out, who might well have many beliefs as to the “reason” for success. You might as well ask a lottery winner the “secret” of their winning. Don L. Jewett University of California San Francisco, US This week’s question A WEE DRAM We often hear about people surviving where water is scarce by drinking their own urine. But can drinking urine – one’s own or anybody else’s – harm you? If so, how? Does it have to be fresh? And how many times can a person recycle it? Obviously, it can’t last forever. Peter O’Brien Dublin, Ireland “Even if each game were totally random there would still be a winner in a penalty shoot-out” 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?
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