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THE LAST WORD Inadvertent omnivore I’m unsure if this is more philosophy than science, but is it wrong for a vegetarian to eat a meat-eating plant?
n No, it’s not. A vegetarian is someone who doesn’t personally consume certain animal products. But such products can make their way into any plant through the soil it grows in. The person eating the plant isn’t responsible for its food chain, and cannot easily determine what conditions it developed in. Karina Robertus Richmond Hill, Ontario, Canada n Carnivorous plants such as the Venus flytrap and pitcher plant are effectively using the bodies of their prey to manufacture their own fertiliser. From this perspective, there isn’t much difference between eating one of these plants and eating a plant fertilised with animal by-products such as bone, blood or fishmeal. These fertilisers are often used in organic farming. Some vegans refuse to eat vegetables produced in this manner. By the way, while I don’t think anyone has ever put one in their salad, the digestive juices of a pitcher plant are said to be sweet and refreshing, at least for desperate travellers in the jungle. Stephen Jorgenson-Murray Frankfurt, Germany
in which all of the vegetables are “fish-eating”. He digs a trench and then goes fishing for a day to fill it with carp from the Murray river. Then he tops it up with soil, before finally plants seeds or seedlings. His crops are much better than most “vegetarian” vegetables. However, as the fish are killed purely to feed the vegetables, I have concluded that his crops are not suitable for vegetarians. Jan Horton West Launceston, Tasmania, Australia
Woolly ideas On a recent visit to Peru, I went to a street market and bought a sweater billed as being made of alpaca wool. Whenever I take it off, it crackles with static electricity. I had thought that this could not happen with a natural fibre like wool, but would need an insulating material like a synthetic fibre. I am not so naive as to believe that the sweater is pure alpaca, but what proportion of synthetic fibre would it need to produce the crackles I experience?
n My brother in South Australia maintains a magnificent garden
n None. Even the purest alpaca, like any other wool or fur, will accumulate electric charge that causes sparking if it is dry enough. Almost all natural fibres will spark if rubbed, although synthetic fibres generally do so more readily. You may observe this inadvertently if you stroke a cat when the humidity is low. The build-up of static can produce sparks that sting its ears or nose
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and leave you with a scratch or a bite. Antony David London, UK n Static becomes a problem when there is a lack of moisture in the air. On a damp day, even polyester won’t crackle. In drier conditions, the water-absorbing properties of fibres come into play, and polyester will suffer more than, say, cotton. Overall, animal hair readily absorbs water. However, the scales on each hair’s surface are nonabsorbent and form a mostly waterproof layer. We enjoy this property: on a drizzly day, a wool sweater still feels dry, even as moisture accumulates. Martin Bide Department of textiles, fashion merchandising and design, University of Rhode Island, US
nearer the end, after millions of years of competition in which the largest tended to win. But when things went wrong, the biggest species also died out fastest. It then took the mammals perhaps 20 to 40 million years to produce land giants, and theirs were smaller than the biggest dinosaurs. That might be because there was less oxygen in the air at the time. In another 120 million years, mammals might beat the dinosaurs – except that extreme size is no advantage against guns and other human technology. We may be what stops land animals from ever rivalling the dinosaurs. Jon Richfield Somerset West, South Africa
This week’s questions SKIPPING TIME
Big beasts After the dinosaurs died out, why didn’t the remaining animals grow as big as dinosaurs again?
n Most dinosaurs weren’t particularly large, especially if we count birds. Also, the largest animal we know of is alive today: the blue whale. Still, dinosaurs were the giants on land. Mammals became dominant only in the past 65 million years or so, after dinosaurs had lasted more than 180 million years, almost three times as long. Generally, the giants evolved
My 9-year-old son and I have noticed that skipping seems like a more efficient form of locomotion than jogging. It is quicker, less tiring and hurts the knees less. Are we imagining this or is there an explanation? And can we make it socially acceptable for me to skip around our neighbourhood? Ken and Ronan Smith St Catharines, Ontario, Canada MOLAR TWINGE
What is that weird feeling I get when I place a metal spoon on my teeth? Michael Airs Uralla, New South Wales, Australia