Earth and Universe, CD-Rom for IBM and compatible computers, Bradford Technology, Angel Way, Bradford BD7 1BX, Pounds 49 plus VAT or Pounds 149 for site licence.

Bradford Technology continues to produce valuable educational material on compact disc, and the company’s latest CD-Rom is a useful addition to a growing list.

Earth and Universe covers a large part of strand v of attainment target 4 of the national science curriculum, at key stages 3 and 4. Indeed, some of the material (especially on gravitation) covers topics beyond these stages. The production of the disc has been supported by the widely respected Armagh Planetarium and this has been an obvious help in explaining such topics as space flight, galaxies, the life of stars, and eclipses.

The disc is well structured and built around a main menu which offers a choice of Introduction, Observations and Explanations, the Solar system, Stars and Galaxies, Gravitation, and Exploration and Satellites. The menu also offers a study guide, a glossary, and nine short quizzes, each with five multiple-choice questions.

The study guide is one way into the contents of the disc, in that it offers items or areas for study and the user simply clicks on a key word or topic to move straight into the appropriate part. The glossary is also a useful feature for learners (and teachers) in offering definitions and explanations of terms used in the disc. Again, this is easy to use and simply involves clicking on the required term - it will be especially valuable for revision purposes, as indeed will many parts of the disc.

What about the explanations of some of the more difficult topics and concepts in this part of the national curriculum? Generally they are clear and the voice of Peter Jones (of the Hitchhikers’ Guide) will make them more palatable and attractive to the learner. Animation, which can be clicked on and off, will also help in explaining, for example, night and day, and the seasons. These are surprisingly difficult concepts for young, and sometimes older learners - remember the national survey of the public understanding of science, which showed that one third of the UK population was not aware that the Earth goes round the Sun?

This disc uses a red spot showing a location on Earth (which appears to be somewhere in Florida) moving in and out of shadow, and explains that the spot moves nearer and nearer “towards the edge of the shadow” as night wears on. I am sure that students of many ages will find the explanations and the animation valuable in clarifying some of their own ideas.

Among the more difficult phenomena to explain are the daily tides we look forward to experiencing at the seaside, but dread when our children ask for a proper explanation. The difficult thing to explain is that there is a “bulge” on both sides of the Earth, due to a combination of the Moon’s gravity and the fact that the two massive bodies involved are rotating. The text on the disc attempts to explain this, and the fact that the time of the tides changes slightly each day. Unfortunately, like most textbooks and articles, it will leave users about as clear as when they started. The use of language like “gravitational effect” and rotation “about a common centre of mass” will not help at his level.

There is also a sentence containing no fewer that 45 words which should not be allowed to slip through.

In summary, though, this disc will be a useful teaching and learning aid in every school or college which is obliged (by law) to face the challenges of explaining the solar system , gravitation, eclipses, the seasons and night and day. Any medium which can help learners and teachers to expose and explore their ideas in this field is well worth the cover price.