Science: Technoquest

Q. What is the latest theory on Stonehenge?

Latest thoughts are that it was built as a monument to create regional unity, in a time when the area was in crisis after the land had been exhausted by cultivation. It took 1,500 years to build and was used as a communal "place" or temple. The South Bank complex, built to bind the nation together after the Second World War had a similar function.

Q. How does a SQUID work?

SQUIDs (Superconducting Quantum Interference Devices) are capable of measuring extremely small currents, voltages and magnetic fields. They are used for, amongst other things, measuring the very small currents generated by the brain - so you can see people think. SQUIDs use superconducting materials which, when cooled to a low temperature, exhibit unusual properties. One of these properties is the ability to trap an electromagnetic field, so that we can measure tiny changes in it.

Q. Why are so many drugs addictive?

People can get addicted to all sorts of substances, including alcohol, nicotine, cannabis, opiates, cocaine, antidepressants and even chocolate. Scientists think that addictive substances stimulate a "pleasure pathway" in the brain. Making certain activities pleasurable - such as eating, drinking and sex - ensures that we continue these essential functions, which aids our personal and species survival. Addiction probably happens by the same system, but it is often harmful rather than helpful. Addictive drugs seem to affect the pleasure pathway so that the person needs more and more to get the same feeling. Stopping generally leads to distressing withdrawal symptoms, which tend to push the addict back towards use of the drug.

Q. Why do racing cars have fat tyres?

Tyre size is controlled by "maximum shear force", which determines a car's turning capabilities. The equation for this is: maximum shear force equals normal force multiplied by coefficient of friction. Therefore, if the area of contact the tyre makes with the surface is great, the pressure is reduced, the coefficient of friction is increased, the maximum shear force increases - and the car can corner at high speeds.

Q. Where does newspaper ink come from?

Newspaper ink is made from carbon black, which is finely-divided carbon produced by the incomplete burning of hydrocarbons, such as methane. The pigment particles are very fine and, because it is up to 95 per cent carbon, intensely black.

Questions for this column may be sent via e-mail to sci.net@campus.bt.com

You can also visit the Technoquest Web site at http://www.sciencenet.org.uk

Questions and answers are provided by Science Line's Dial-a-Scientist on 0345 600444