The world can seem a big place when you are 10 years old. Year 5 pupils from Reigate Priory School in Surrey are trying to figure out just how big. “If you set off walking round the Earth and you never stopped to sleep or to eat, you just kept on walking and walking, how long do you think it would take you to go all the way round the world and back to school?” asks Matt Fox, one half of Spacefund, a touring theatre designed to introduce primary-age pupils to “the wonders of space”. “Five years?” wonders one boy. “Ten years?” offers another. “If you kept on walking and never stopped, it would take 257 days,” Matt tells them.

Not as big as they think, then. Matt is holding the Earth in the palm of his hand, and he is about to take off from this tennis-ball-sized globe on a scaled-down tour of the solar system - from peanut-sized Pluto to Jupiter, which is really a four-foot-wide physiotherapist’s ball in disguise. The Sun is represented by a novelty standard lamp - a scale model would be the size of a hot-air balloon.

Matt dresses up as the intrepid astronaut while his partner Joanne Northway is the captain of the spaceship and the pupils assembled in Reigate Priory’s handsome 18th-century hall are her crew. Jo runs a tight spaceship, and crew members have to salute whenever they see her do the same. This proves a clever way of winning back their attention when Matt’s slapstick routines - hopping around on the sizzling 350-degree surface of Mercury - threaten to distract the audience. You need to be disciplined on a spaceship, after all.

Real-life partners Matt and Jo began Spacefund last year as a way of combining their talents (she was a teacher, while he trained as an actor) with a shared enthusiasm for outer space. They also hope to instil in pupils a sense of exploration, respect for the planet, a smattering of science and “the feeling that their potential is as limitless as the stars”.

But they use a refreshingly down-to-earth approach to bring home the physical conditions on faraway planets, covering the curriculum key stage 1 and 2 areas of Light and Sound, Forces and Motion and The Earth and Beyond.

Because its gravity is one-sixth of that of the Earth, walking on the Moon is “a lot like walking on a trampoline”, iron-rich Mars is red “because it’s rusty” and its dramatic, dusty landscape is “like something from the Wild West”. Difficult concepts such as Jupiter’s lack of a solid surface are easily explained: trying to walk on its swirling gases is “as impossible as it is for one of us to walk on a cloud”. Spacefund also runs a Kids in Space Club and a website which offer more in-depth explanations of the concepts on show.

Teachers at Reigate Priory were enthusiastic about the show (one even admitted “I never knew Pluto was so small”) and, with worksheets to follow up Matt’s and Jo’s on-stage antics in class, they felt its entertainment value was matched by educational content.

The one-hour performance ends with a rewritten nursery rhyme to illustrate the fact that stars are really just suns in other solar systems: “Twinkle, twinkle, giant star, larger than the Sun by far. Since your distance is a lot, you look like a tiny dot.” More galactically than grammatically correct, but like the rest of the show, memorable.

* Performances cost from pound;200, with workshops extra. Spacefund, Observatory House, St Radigunds Street, Canterbury, Kent CT1 2AA. TelFax: 01227 459 485. E-mail: spacefund@hotmail.com Web: www.spacefund.co.uk