The Greenwich Guides interpret various aspects of time for an audience of seven-to nine-year-olds. The presentation is straightforward, with equal space for pictures and text. Photographs from the Greenwich archives are well chosen, but inevitably problems arise where still graphics attempt to explain dynamic concepts. The concentration of young readers will be tested as they trace each stage in a changing scene.

All three books take an astronomical perspective. In Seasons, the earth’s orbit and axial tilt are keys to understanding. Anyone who has taught this topic to primary children will know the pitfalls for teachers and pupils, but this book helps clarify quite complex ideas.

Measuring Time discusses the broader time periods of the calendar before describing timekeepers of different eras, culminating in the atomic clocks of today.

Day and Night explores the effects of earth’s rotation, shadows and time zones, then views the night sky with seasonal stars and the Moon’s phases. The lack of direct early reference to there being 24 hours in a day is somewhat puzzling. Earth’s 24-hour rotation is assumed and a later chance to refine the period (to 23 hours, 56 minutes, 4 seconds) is then lost. Children enjoy this sort of precision, especially when it differs from generally accepted approximations.

So when the glossary states that a year is made up of 365 days, we can almost hear the chorus “and a quarter”. The line between clarity and over-simplification is difficult to draw, so these are minor complaints about a trio of books which provide a competent introduction to the chosen themes.

DENNIS ASHTON