technoquest

Q Was Teflon developed in the Manhattan or Apollo projects?

A The story of Teflon begins long before either of these projects, on 6 April 1938 at Du Pont's Jackson Laboratory in New Jersey, in the US. Dr Roy J Plunkett was working with gases related to Freon (which was being used as a refrigerant). When checking a frozen compressed sample of the gas tetrafluoroethylene, he found it had spontaneously polymerised into a white waxy solid, now known as polytetrafluoroethylene (PTFE). This and similar chemical compounds developed since have been given the commercial name Teflon. So, in fact, the discovery of Teflon was a complete accident. It may well have been used in the Manhattan and Apollo projects, but it was not invented for them because it was not really invented at all.

Q Why does clear water freeze into cloudy ice cubes?

A Three factors contribute to distortion of the image seen through the ice cube:

Ice is made up of many crystals all stuck together, not one great big crystal. This means there are lots of edges within the ice around which diffraction of light can occur.

Gases including CO2, N2 and O2 are less soluble in cold water than warm water, so as part of the cooling and freezing process millions of tiny gas bubbles are formed in the ice as gases come out of solution. These cause distortion due to refraction.

Small pockets of water remain liquid at points within the ice structure that are under high stress. Again these cause refractive effects, making the ice opaque.

Q Why don't the infrared key fobs used to turn car alarms off not interfere with other car alarms?

A These car fobs work using a specific code rather than a general frequency. Each emits a series of infrared pulses unique to each car. This system is quite old: now car manufacturers use an ultrasound-based system for which each car has a different frequency.

Q The weather is cold in winter: is that because the Earth is farther from the Sun during winter compared with summer?

A The Earth does not orbit the Sun at 93 million miles all the time; that is an average figure. At different times of the year it gets closer and farther away than this. During the northern hemisphere's winter the Earth is actually closer to the Sun than during the summer. What makes the difference to the weather is the way the Earth is tilted on its axis. During our summer, the North Pole points towards the Sun and much more sunlight (and therefore heat) falls on a given area of the Earth's surface than during the northern hemisphere's winter, when the South Pole is directed towards the Sun.

Q Are we still moving because of the Big Bang explosion at the beginning of the Universe?

A Apparently, yes. Light from distant objects beyond the confines of our galaxy, the Milky Way, behaves like the sound from a receding fire engine: the frequency is lower than it should be. From this "doppler shift" we infer that we and the rest of the Universe are still feeling the effects of the Big Bang.

These questions and answers are provided by Science Line. You can contact its Dial-A-Scientist service on 0345 600 444.