Fruit salad solar system
Grasp the ungraspable! Using the contents of your fruit bowl, you can help your little one appreciate and understand the staggering scale of our solar system
This hands-on exercise looks at some of the main differences between the four inner terrestrial planets; Mercury, Venus, Earth and Mars, and the four giant outer planets; Jupiter, Saturn, Uranus and Neptune. Using the contents of your fruit bowl, you and your child can discuss the contrasting structures and compositions within our mind-boggling planetary system. Best of all, you can eat this experiment afterwards!
Learning about the size of the planets and stars
To understand the scale of our close neighbours – the rocky, terrestrial planets – you will need:
Mercury – a peppercorn
Venus – a blueberry
Earth – a marginally bigger blueberry
Mars – a cranberry
To understand the scale of our distant neighbours – the gaseous, giant planets – you will need:
Jupiter – a grapefruit
Saturn – an orange
Uranus – a small satsuma
Neptune – another small satsuma
To understand the scale of the sun – the largest star in our solar system – you will need: an exercise ball, and your very best concentration faces.
- Get your child to line up all of the different fruits in the correct order – starting with the peppercorn Mercury, and ending with the satsuma Neptune.
- With younger children, you will likely need to tell them which fruits represent which planets upfront. With older children already aware of the solar system, you may wish to challenge them further by having them guess which fruit represents which planet. Can they guess correctly? Can they explain the reasoning behind each guess?
- Once your child has lined up all of the fruit planets, talk to them about the relative sizes. Which planet is the smallest? Which the biggest? Are there any planets that are similar in size? Are they surprised by any of their findings?
- Teaching your child about the size of the sun is a little trickier, as there are no fruits large enough to represent it. However, you can use an exercise ball if you have one to hand.
- Hold the ball up next to the blueberry Earth for context.You can explain the impact of the sun’s heat by talking to your child about the conditions on Earth in comparison to the conditions on our neighbouring planets.
- To explain this, you can tell them life on Earth (as we know it today) evolved due to the right conditions (temperature, radiation etc) on the planet, which in turn was possible because of Earth’s fortunate position in our solar system. For millions of years, we have adapted to live in these exact conditions. If Earth was to change its position and move slightly closer to the sun, the temperature and the amount of radiation on earth would increase, thus making it difficult for any life form to survive here. Even the smallest changes could have huge consequences, but for now, we are most lucky indeed.
Learning about the density of the planets
To understand how the atmosphere of each planet affects its density, your child will need: a vase of water, a grapefruit (representing Jupiter), and an orange (representing Saturn).
- Get your child to place the grapefruit Jupiter into the vase of water. What happens to it?
- Get your child to place the orange Saturn into the vase of water. What happens now?
Results and guidance
- The grapefruit Jupiter should sink to the bottom of the vase. Though Jupiter has a solid core, it is largely made up of hydrogen – the lightest of all gases. On this basis, we might expect Jupiter to be relatively light, and to float to the surface of the water. However, even though Jupiter is made up of this light gas, it is surprisingly dense and heavy. This is because this gaseous world rotates very quickly. While the earth rotates in 24 hour cycles, Jupiter rotates in just 10. The planet’s subsequent giant gravity squeezes the hydrogen gas so that it becomes denser than water. As a result, it will sink.
- The orange Saturn should rise and float when it’s dropped into the water. Like Jupiter, Saturn is also made up of hydrogen. However, its mass is less tightly squeezed, which means it’s less dense, and will float if dropped in water.
- 1 hour
- A peppercorn, two blueberries, a cranberry, a grapefruit, two small satsumas, a vase of water (optional), an exercise ball (optional)
- Aspiring astronauts