Solar system for toddlers: what my 20-month-old actually understands

By Anand Yadav · @summiva.app · Posted 25 May 2026 · 6 min read

I opened the Reader's Digest Family Guide to Nature to the solar system page and pointed at Jupiter. "Ball," said Aanya. I turned to Saturn. "Ball." Mars. "Ball." Neptune. "Ball."

She was about 12 months old. Every round thing in that book was a ball. Every round thing in the world was a ball. And that, I have come to realise, is exactly what comprehension looks like at this age.

What a toddler sees when you show them the solar system

A toddler does not see planets. They see shapes and colours. Jupiter is a big orange-brown circle. Saturn is a circle with lines through it. Earth is a blue circle. The sun is a yellow circle. At 12 months, Aanya had exactly one category for all of these: ball.

This frustrated me at first. I wanted her to say "planet" or at least "Jupiter." I had to remind myself that she had been alive for 365 days. She was working with maybe 30 words. Ball was a perfectly rational classification for a round object she could not touch.

The shift happened slowly. By 14 months, "ball" was still her word for all planets, but she started differentiating one from the rest. The blue one with white patches became something she would point to and wait for me to name. I said "Earth" every time. By about 16 months, she said something close to "Ehh" while pointing at it. By 18 months, she calls it "ball and water" which is, if you think about it, not a bad description of Earth.

The lesson for me was that toddlers do not learn the solar system. They learn shapes, then colours, then names, then associations. The solar system is just the material.

The three words that stuck by 18 months

Out of all the space vocabulary I said out loud over six months, three words survived into Aanya's active vocabulary by 18 months.

Moon. This was the first and easiest. She learned it from three sources at once: the real moon on our evening walks (I pointed and said "moon" every time it was visible), the sky projector moon disc on her ceiling at bedtime, and bedtime story books that happened to mention the moon. The repetition across three contexts is what made it stick. She was saying "moon" unprompted by about 14 months.

Sun. This one came from the Ask Me Everything book we had at home. It has a cross-section diagram of the sun with orange and yellow colours. I called it "sun" and added "hot" because she already understood hot from food. "Hot ball" became her phrase for it around 16 months. She does not point at the real sun outside because we told her not to look at it directly, which she mostly respects.

Earth. The "ball and water" moment I mentioned earlier. This took the longest because Earth does not appear in our daily life the way the moon and sun do. You cannot point at Earth. She learned it purely from book pictures, over about four months of irregular exposure. The Reader's Digest photo of Earth from space, showing blue oceans and white clouds, is the image she responds to.

Three words in six months. That is the pace. Anyone expecting a toddler to name all eight planets is expecting the wrong thing.

What they do not understand yet, and that is fine

Aanya does not understand that Earth is a planet. She does not understand that we live on it. She does not understand that the moon goes around Earth, or that Earth goes around the sun. She does not understand size, distance, gravity, orbits, or why the moon changes shape.

I tried explaining moon phases once, at about 15 months. I held a ball and a torch and moved them around to show how shadows work. She grabbed the torch and tried to eat it. That was the end of that lesson.

The instinct to explain is strong, especially if you are the kind of parent who finds space fascinating. But explanation is a tool for children who already have the vocabulary and the curiosity to ask "why." Toddlers are not there yet. They are building the raw vocabulary: what things are called. Understanding what those things do comes later, when the words are already in place.

My rule now: name things. Do not explain things. If she asks why, answer simply. If she does not ask, do not volunteer.

The weekly rhythm that worked for us

I did not plan a curriculum. I do not have a chart on the wall tracking which planets Aanya can name. What we have is a loose rhythm that repeats most weeks without effort.

Most evenings, we go for a walk outside our home. If the moon is visible, I point at it. She points back. She says "moon." That takes about 15 seconds. Some evenings the moon is not visible, and we skip it.

Most nights, the sky projector runs at bedtime. She watches the moon disc on the ceiling while we settle her down. Sometimes I switch to the Earth disc. She says "ball and water." The projector has a 30-minute timer and turns off on its own.

Two or three times a week, she brings me the Reader's Digest book or the Ask Me Everything book. She flips to the pages she likes. Sometimes those are the planet pages. Sometimes they are the animal pages. I name whatever she points at.

No apps. No videos. No screen time of any kind. Our paediatrician recommended no screens until age two, and we follow that. Everything Aanya knows about space came from books we already owned, a cheap projector, and the real sky.

If you use Summiva for an astronomy goal, the weekly checklist generates activities like these, matched to your child's age. The app does the planning. You bring the books, the walks, and the bedtime projector. For the full age-by-age guide, see astronomy for kids at home.

What I would do differently

I started the sky projector when Aanya was 12 months old. Looking back, I think 9 months would have worked. She was already tracking ceiling lights at that age, and the projector is just a different kind of ceiling light. Starting earlier would have given her three extra months of passive exposure to the moon image before she had words for it.

I would have bought Hello, World! Solar System (the board book) earlier. We relied on the Reader's Digest and Ask Me Everything books, which worked, but they are adult reference books. The text is too small, the pages are too thin, and she cannot hold them without help. A proper board book with one big planet per page would have been more independent for her.

I would not have tried to explain moon phases at 15 months. The torch-and-ball demonstration was a waste of both our time. She was not ready. I will try again at about 2.5 years, or whenever she starts asking "why does the moon look different."

And I would have relaxed sooner about the pace. Three words in six months felt slow to me in the middle of it. Looking back, it was exactly right. She built a foundation of real, grounded vocabulary that she uses every day. That is more valuable than a list of planet names she would have forgotten in a week.