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The Hindu Speaks On Scientific Facts - Volume II

General: Applied Science and Technology

During winter, in the U.S. people add salt to melt the unwanted snow (on the roads). But in India, to make ice-cream we were advised to add salt to the ice cubes amongst which the ice-cream is kept. Can anyone explain the role of salt in these situations? 216 Why molten wax which is transparent becomes opaque at normal temperature? 217 Why are iron pipes laid down in the entrance of some main buildings? 217 Why do people swat more before a heavy rain? 217 What is a biological weapon? 218 What is the role of superplasticizers in concrete? When are they preferred? 219 A newspaper is easily torn vertically but not horizontally. Why is it so? 220 It is slightly difficult to neatly tear a dry sheet of paper. Also when torn, it produces noise. But it is easiear to tear a wet paper, that too without noise. Can any one explain this? 222 Why does paper become translucent when smeared with oil or fat? 223 Steam produces greater burns than boiling water. Why? 224 What is the name of the dreaded black mould that colonises damp places in bathrooms? Because materials produced to remove the mould do not seem to work, and nor do household bleaches, detergents and solvents, can anyone suggest a remedy other than abrasives? 226 What is the difference between bacteria and virus? 227 When there is a light in a certain position, I see chromosome-like structures about a metre from my eyes. They change shape and move wherever I look. What are they and does everyone see them? 228 Why do finger tips become white and cold when we put rubber bands around them? 230 Why do eyes produce tears when tear gas is used? 230 How do race organisers time cyclists? If they do it by video, how do they get separate times from the hundreds of riders who cross the finishing line at the same time? 231 What is computer simulation technique? 232 What are supercomputers? 233 Is it true that condensed milk has more fat than ordinary milk? 235 What are artificial teeth made of? 236 What is an aqualung? 237 Why is fire hot? 238 How is knocking reduced in vehicles using unleaded petrol? 239 Nickel-cadmium cells used in rechargeable torch lights, shavers, etc. are said to have a memory effect. What is this memory effect and how does this affect the battery performance? 240 Does sewage discharge into the sea harm marine life? 242 Why does our hair change its colour as we age? 244 Why are the wing tips on modern passenger jets upturned? 245 How is honey naturally nutritive? Do all flowers have the same composition? 246 How can we test the purity of honey? 247 Why does a corpse float on water, when a living person must exert an effort to stay afloat? 248 After I take a hot shower and the hot, wet air from the bathroom combines with the cold air from the hall, why doesn't it rain in my house? 248 Why does snow melt faster around a tree trunk? 249 What is the difference between butter and cheese? 249 While some motor vehicles belch smoke, some are very clean without any visible smoke coming out of their exhaust. What makes them differ? Is there any simple way to control this pollution? 251 Why do we become unconscious when hit on the head? 252 What is the principle behind breath analysers used to detect drunken-driving 253 How do we calculate the fat per cent in milk? 253 Can we use methanol or ethanol bio-fuels in motor vehicles and pumpsets? Is it helpful in reducing pollution? 255 Why is fuel used in airplanes different from those used in motor vehicles? 255 Why do fingernails grow faster than toenails? 257 Why is Sriharikota a place suitable for launching rockets? 257 The last time I went to the Empire State Building (in the U.S.), it looked as if the building was swaying. Is this an illusion? 259 How does a water diviner work? 260 What is the advantage of sucking a cut finger? 261 What is automatic mail processing unit? 262 Why is the @ symbol used in an email address? 263 How does ballast-less track provide safe travel? 264 What is the pH of rainwater? Is the pH suitable for drinking? 264 Are the vocal cords of professional singers wired in such a manner as to make their voice mellifluous? 265 How do people walking on burning coal not burn their feet? 267 Soaps come in different colours. But why is soap's lather always white in colour? 267 How is a ventrilouist able to throw his voice 268 Why do we see rainbow colours on a CD? 269 Breast-fed babies brainier? 271 You are human if you are hairless 274 The smells of silence 277 Leech: the parasite physician 281 Life in fire and brimstone 283 Who can see well under water? Moken! 287 Science's top ten achievements of 2001 291 Top ten achievements during 2002 298 Top ten breakthroughs of the year 2003 304 Index 309

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