**Description**

The programme examines a number of methods of measuring distances in the earth-moon system such as the circumference of the earth, diameter of the moon and the distance between the earth and the moon.

Module code and title: | S101, Science: a foundation course |
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Item code: | S101; 02 |

First transmission date: | 27-02-1979 |

Published: | 1979 |

Rights Statement: | |

Restrictions on use: | |

Duration: | 00:24:00 |

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Producer: | John Stratford |

Contributors: | Keith Hodgkinson; Steve Swithenby |

Publisher: | BBC Open University |

Keyword(s): | Measurement |

Subject terms: | Distances--Measurement; Earth (Planet); --Moon |

Footage description: | Film of pupils at Bishop Walsh School in Sutton Coldfield doing a reconstruction of Eratosthenes' experiment to measure the circumference of the earth. Keith Hodgkinson introduces the programme. More film shots of the above experiment being set up and of data being collected. Hodgkinson explains what is happening. Steve Swithenby, with the aid of a drawing board, explains the principles governing the experiment. From the data collected by the pupils, he begins the calculation to determine the earth's circumference. Swithenby continues to explain the method for calculating the earth's circumference. A map of Egypt, one of the UK, and an animation all help to illustrate his points. He then carries on with the preliminary calculations but leaves the final calculations for students to finish at home. Keith Hodgkinson explains, with the aid of an animation and a model of the earth, why one of the assumptions of the above experiments, that the sun's rays falling on earth are parallel, is not valid. Keith Hodgkinson goes on to describe an experiment, devised by Aristacus 2000 years ago, for determining the diameter of the moon. He uses a model of the earth/moon system to illustrate his points. Steve Swinthenby, using a drawing board, does the Mathematics for the above experiment. Film of Hodgkinson taking measurements with the Home Experiment Kit (disc on a pole) for an experiment to determine the distance between the earth and the moon. The experiment is not performed on the programme but Hodgkinson discusses some of its key points to help students who will be doing it themselves later. A more modern and accurate method for determining the earth/moon distance, by use of lasers, is taken up by Hodgkinson. He begins by demonstrating the properties of lasers which make the measurement possible and then goes on to explain how the experiment is done. |

Master spool number: | 6HT/72922 |

Production number: | FOUS002N |

Videofinder number: | 1177 |

Available to public: | no |