Original: Space is a huge, mostly empty place with stars and planets scattered like sprinkles. It stretches in ways that are hard to imagine, and that's why we call it boundless.
Corrected: Space is a huge, mostly empty place with stars and planets scattered like sprinkles. It stretches in ways that are hard to imagine. That's why we call it boundless.
What I changed and why (easy steps):
- The original sentence was already grammatically correct. Nice work!
- I split the second sentence into two short sentences to make it easier to read: "It stretches in ways that are hard to imagine." and "That's why we call it boundless." Short sentences are often clearer for young readers.
- All words and punctuation are otherwise fine: commas, word order, and the contraction "That's" are correct.
Kid-friendly meaning: "Boundless" means it seems to have no edges or end — it goes on and on. That's why we say space is boundless.