My kids know the names and order of the planets in the solar system, but I decided I needed to teach them how to compare planet sizes. I wanted to answer their continual questions. ”How big is Earth compared to Jupiter?” “Is Earth bigger than Mars?” “Which is the biggest planet?” And so on.
My aim was for them to understand the relative sizes of the eight planets in our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
So these are the two fab ways I discovered to teach my kids how to learn about and compare planet sizes.
3D how to compare planet sizes: If Earth was a cherry tomato
My inspiration to compare planet sizes was the result of buying the book Professor Astro Cat’s Frontier of Space by Dr Dominic Walliman and Ben Newman.
Inside Astro Cat’s book was a drawing showing the different sizes of planets and comparing them to a peppercorn, large blueberry, cherry tomato, pea, watermelon, large grapefruit, apple and a lime. So cool!
What I liked about this way of looking at planet scale was that it gave my kids a chance to see and compare in 3D the different sizes of planets.
We also discussed some of the planets’ attributes. For example, we talked about how Jupiter is the biggest planet in the solar system but it’s just a big ball of gas. So, although we were using a heavy watermelon to show its size, as Astro Cat explains, “If you tried to land a spaceship on Jupiter, you would fall straight through the surface.”
They knew Mercury was the closest to the sun, but they discovered it was the smallest planet in the solar system. Like a peppercorn.
2D how to compare planet sizes: if Earth was a drawing
Then I decided my kids needed to find out about relative sizes of the planets in a hands-on creative way. Everywhere I looked the explanations and comparisons were for adults or older kids, so I created my own method for them to learn how big earth was compared to the seven other planets in our solar system. I worked out the rough scale for each planet using the information from a NASA chart on the relative size of planets to the sun and compared to Earth. (Free printable of my chart available below)
With the help of a circle template for the smallest planets, a compass and a ruler, I drew each planet for my kids to color in and cut out. Older children can do this for themselves – actually a great way to practise measuring and using a compass.
Both of them told me they were going to color the planets the correct shades too.
Free printable of chart with planet size measurements
I’ve included a free printable chart of the measurements in centimetres (British spelling!) and inches to draw the planets. These PDFs available in both Letter (US) and A4 (British) sizes.
DOWNLOAD HERE -> How to draw planets of the solar system to scale (Letter)
DOWNLOAD HERE -> How to draw planets of the solar system to scale (A4)
(Note – the printables and charts can be used for personal use only. No commercial use as I retain the copyright. Feel free to contact me if you would like to feature this chart – I would need to be credited as well as a link to this post)
Want to find out more about Professor Astro Cat’s Frontier of Space by Dr Dominic Walliman and Ben Newman? I’ve written a review of this kid’s astronomy and space book which I highly recommend.
I should have probably done the 2D method first. We learnt, for example, that Venus and Earth were close in size (Earth slightly bigger). Uranus and Neptune are also similar in size (Uranus is the bigger one). If I had seen the planets to scale first on paper, I would have tried to choose fruit closer to the right sizes. But, then again, my aim was not to make exact scale replicas of the planets but rather to help my children understand how the planets compare in size to each other.
We also found a great image showing the planets of the solar system to scale on Wiki (Creative Commons) which we labelled. Yet my kids really understood the different sizes of the planets in comparison to each other by looking, touching, cutting and drawing them. And having fun at the same time!
If your kids are interested in space then here’s some lovely suggestions of space books and toys for them so they’re ready to prepare them for a future day of space travel.
A great fiction book for kids in the wild world of space is Jonny Duddle’s King of Space.
For more space ideas for kids – including my compare planet sizes chart – visit Wild About Here’s Pinterest space board.