Modelling the solar system will always be difficult because of the truly enormous sizes and distances involved. As an example, in a model where the Sun has a diameter of 50cm (19.6 inches), Mercury would have to be a mere 1.7 mm (0.069 inches) in order to be to scale. This means that in practice, it’s extremely difficult to create an accurate scale model. However, it is possible to create a more illustrative and somewhat accurate model of the planets in the solar system using foam balls.
Paint the largest foam ball an orange-red colour to represent the Sun. Cover it evenly, but it doesn’t really matter if some parts are lumpier than others – the Sun isn’t a uniform ball, it’s a searing, constantly active ball of hot plasma. Substitute a mixture of yellow and red if you don’t have suitable orange acrylic paints.
Cover the 2.5 cm ball in an ashen grey paint to represent Mercury. Mix in brown for a more realistic appearance. You can also use the other end of your brush to create some craters across the surface if you like, for a more accurate representation of the pock-marked planet.
Use different colours for each of the three 4 cm balls. Paint one a deep, brownish-yellow to represent Venus, one a warm sea-blue to represent the Earth and the final one a rusty red-brown to represent Mars. These three planets are actually different sizes, but they’re close enough to each other that in this model they can be represented by identical balls. If you have modelling clay, you can create the giant Martian mountain, Olympus Mons, on the surface of the planet.
Paint horizontal bands of colour around the 10 cm ball to represent the bands of gas around the largest planet, Jupiter. Use alternating beige and brownish-red (or light and dark brown) paint to represent these bands, with two large dark patches covering the poles and thin strips around the middle. On the southern hemisphere of the planet, paint a spot of red paint to represent the most striking feature of Jupiter, the Great Red Spot. In reality, this spot is big enough to hold two Earth-sized planets.
Cover the 7.5cm ball in golden-brown paint to create Saturn. Use a foam ring to represent the ring system, the most notable feature of the planet. Paint this a slightly darker shade than the rest of the planet. The rings surround the planet horizontally (from the Earth’s perspective). Use straightened paperclips to hold the ring in place, pushing the tips into the planet and the rings.
Paint both the 6.5 and 5 cm balls blue. Use vertical bands of lighter and darker blues on Uranus, the larger of the two balls, with the lightest band towards one side of the planet. Uranus also has a ring system, which you can attach in the same way as you did for Saturn, except that the rings are vertically aligned, like a cosmic circle drawn around the planet. Paint the rings a mixture of dusty grey and icy blue. Paint Neptune (the final sphere) a more uniform blue.