Science: How town halls save the world

Technoquest

Questions for this column can be submitted to sci.net@campus.bt.com

How do we dispose safely of CFCs?

All local authorities should now offer a degassing service for fridges and other CFC-containing devices. The material recovered can easily be reused depending on how contaminated it is. For example, fridge companies can just filter and remove moisture from the gas before using it again. But if it is taken by local councils, it might need to be distilled to separate out the different CFCs so that it can be used in different applications.

The material extracted by local councils is controlled by several central organisations, and fines are imposed on those who let the gases out uncontrolled.

Where were dinosaurs discovered?

Dinosaurs were first found in the Western world in Britain in 1817, when quarrymen in the village of Stonesfield, in north Oxfordshire, discovered some megalosaurus bones. It was eight years before another dinosaur was found, in 1825, by Dr Gideon Mantell who called the animal iguanodon. Those bones were unearthed near Cuckfield in Sussex.

How do things rust?

To create rust you need water, air and (of course) iron. The reaction is complicated, but essentially the oxygen reacts with the iron, with the help of the water, to make a reddish compound called iron oxide. Be wary of "rustproof" treatments which challenge you to "paint a nail with this and then put it in a jar of water - it won't rust!" If you do this, try immersing an untreated nail too - that won't rust either. .

Why are grandfather clocks so tall?

The longer the pendulum, the longer the swing. To take one second to swing from one side to the other and one second to swing back, a pendulum needs to be almost exactly one metre long - a remarkable coincidence of natural ratios between the Earth's gravity and pi, the circular ratio.

You can visit the Technoquest site at http://www.campus.bt.com/CampusWorld/pub/ScienceNet. Questions and answers provided by Science Line's Dial-a-Scientist, 0345 600444.