DIY Astronomy
Build a model in your garden to reveal the spacing between our planetary neighbours
We have all seen diagrams showing the planets of our Solar System orbiting the Sun. Sometimes their relative sizes are shown, but it is impossible to depict the space between them – the orbital distances of each of them from our central star. Our Solar System is huge and the distances involved are difficult to comprehend, so using scale models helps us to visualise this. As the distances are so big, it’s almost impossible to have both accurate planet sizes and distances in one scale model: if we scaled the distances based on the Sun’s size we used in this model, Neptune would be half a kilometre away! This is not something you can squeeze into most gardens.
For this fun project, we are creating a model that shows the distances at a scale that can fit into a garden or park. The radius of our Solar System has been scaled down to 10m. If our Sun and planets were at the same scale, the Sun would have a diameter of 3cm, but Mercury would be a microscopic 0.1mm, Earth 0.2mm and the largest planet, Jupiter, just 3mm. Obviously we can’t replicate that for our model. Instead, we’ll be using polystyrene balls of different sizes to show that the planets vary in diameter, but they aren’t at any specific scale relative to each other or to the distances. We’ll place our planets in a straight line, but they would really extend out by 10m in all directions from our star.
The distance between the Sun and the Earth is 150,000,000km; this is 1 Astronomical Unit (AU). To make the maths simple when calculating the distances for our model, begin by working with a scale of 1 AU to 1 metre. With Neptune at 30 AU, it means the model would be 30m, which is still larger than most gardens. Indeed, we only had 10m to work with. But as this is three times smaller, we got the distances in metres for each planet down to a manageable scale by dividing the AU for each planet by three. You can adapt this calculation to fit your garden, park or green space.
The distances from the Sun for each of the planets are in our downloadable table (see below for instructions). We’ve also included the inner and outer edge of the asteroid belt. We painted our Sun and planets an appropriate solid colour so they would show up better in photos, but you can add surface features and the rings of the four giant planets.
The end result will give you an invaluable insight into the distances in our planetary neighbourhood.