Tuesday 17 June 1997
Q Why are there 360 degrees in a circle?
This trend began with the ancient Babylonians in around 700BC. They measured things using a number base of 6 - hence the 60, just as we measure things in base 10, hence the 100. (The number 10 does make division and multiplication easy.) The number 6, and multiples of 6 like 360, are great for division: think how many divisors 360 has. Modern mathematicians did try to "decimalise" the circle by devising a measurement called the radian. By definition, there are 2 radians in a circle. Physicists, engineers and mathematicians use radians because they make many equations easier to manipulate. But builders and DIY enthusiasts find degrees much simpler - after all, would you know offhand how much of a circle 1.5707 radians represented?
Q Why does dog faeces eventually turn white?
In the past there were two reasons. The first was diet. Dogs were fed home-prepared food with bits of bone in it, which put small chips of white material into the faeces. However, bone can cause all sorts of problems for dogs - from chipped teeth to scratched oesophagus. It can cause salmonella, and constipation. Modern dog owners prefer to use a prepared food with a milk-based calcium source, so dog faeces is no longer white because of bits of bone.
The other reason is that a mould starts to grow on the faeces if it's left for long enough. The mould - a yeast - takes three or four days to grow. But these days councils tend to clean the streets more quickly, removing the faeces before the mould turns it white.
Q How does hi-fi surround sound work?
It depends on how many speakers you have. A two-speaker system sends out a delayed "echo" of sound that's much quieter than the initial burst. You can alter the length of delay between the original sound and the echo to give the effect of a large hall, small room, etc. With four speakers you just position the speakers around the room to make it sound like the sound is coming from all around you. Some hi-fis can let you control the "delay" to the rear speakers to make your room seem much bigger.
Q How do plants know what the seasons are?
Every plant has a biological clock that responds to temperature and light. With bulbs, small miniature plants with flowers develop within the bulb during the previous season (or in autumn, for spring blossoms). Each type of flower is programmed to start growing a specified number of months after the formation of this miniature plant (for example, tulips wait five months). After this wait, the bulb begins to let water enter the cells of the miniature plant. This makes the cells swell and elongate, so the flower, stem and leaves grow bigger until they are fully grown. After the stem begins to grow, the growth rate depends on the temperature. If the weather is warm, the plant will grow faster and will bloom earlier.
Q Could a cockroach survive in a microwave?
At high power levels, cockroaches do not survive. The microwave energy causes the insects to "pop" as their body fluids heat up. At low power levels they can sometimes survive. This is probably due to some property of their integument or outer skin. The oils in it may reflect enough energy to prevent popping.
You can also visit the technoquest World Wide Web site at http://www.campus.bt.com/CampusWorld/pub/ScienceNet
Questions for this column can be submitted by e-mail to firstname.lastname@example.org
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