A mechanical model of the solar system. Mercury, Venus, Earth, Mars, Jupiter and Saturn orbit the Sun at their correct relative speeds. The speed can be continuously varied (both forwards and backwards), to allow phenomena such as the retrograde motion of Mars to be clearly demonstrated. A model of the Moon orbits Earth. The removable dome shows the night sky in the northern hemisphere. Also supplied is a larger version of Earth in the form of a 100 mm diameter globe, for illustrating the seasons, diurnal variation, phases of the moon, etc.