Why is British weather so unpredictable?
4 March 2012 Last updated at 08:55 GMT
The Earth whips around its axis, with the equator whizzing around at nearly 1,700 km an hour (over 1,000mph). This rotation has a particularly powerful impact on British weather.
Dr Helen Czerski explains how cold polar air from the north and warmer air from the Tropics push against each other to create the UK's changeable weather and unpredictable winters.
Part one of Orbit: Earth's Extraordinary Journey is on BBC2 at 21:00 GMT on Sunday, 4 March and is available online afterwards on the BBC iPlayer.