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Today we explain what produced the mysterious ice spike that appeared in a frozen beaker of water. A skilled motorcyclist can stay upright at very low speeds. The wheels help by acting as gyroscopes but is the effect enough to explain such slow stability? We discover why rays of sunlight seen emerging from behind clouds appear to be pointing in different directions. Discuss the practicalities of scavenging trace amounts of precious metals from dirty water. And does the gravitational tug of the Sun and Moon have an effect on volcanic activity here on Earth. Doing the thinking this week are Dr Jo Baker of the journal Nature; Dr Ehsan Masood of Research Fortnight and Professor Philip Stott, an environmental scientist from the University of London. Contact: ÃÛÑ¿´«Ã½ Planet ÃÛÑ¿´«Ã½ Radio 4 PO Box 3096 Brighton BN1 1PL Or email home.planet@bbc.co.uk Presenter: Richard Daniel Producer: Toby Murcott A Pier Production for ÃÛÑ¿´«Ã½ Radio 4.