Earth & Space Ladder · Free, middle school to college
Climb from rocks and rain to plates, climate and the planets
Short lessons that build each idea from the ground up, worked examples, and practice that checks your answers and shows every step, on the planet under your feet and the sky above it. No sign-up, nothing to pay.
The ladder
Each rung is a full course. Start where you are; topics from earlier rungs come back when you need them.
How the Earth & Space Ladder works
- Find your rung. A short check, at most 30 questions, skips what you already know and finds your starting point.
- Learn from first principles. Each topic is one small idea. The lesson shows why it works, then walks through worked examples one step at a time.
- Master it before moving on. Three right answers, the last two in a row, pass a topic. If a topic gets hard, we point you to the skill underneath it.
- Review, spaced out. Passed topics come back after 1 day, then 3, 7, 16 days and longer, for two quick problems each. Harder topics that use an older one count as practice for it.
- Mix it up. Reviews and checkpoint quizzes mix problems from different topics, so you learn to tell which method a problem needs.
- Earn XP. About one point per minute of focused work. Set a daily goal and keep your streak going.
- One climb across subjects. Every ladder shares your XP, streak and reviews. When a topic needs a skill from another ladder, such as the algebra behind a formula, that skill comes first, labeled with its ladder.
Why these steps: the U.S. Institute of Education Sciences practice guide Organizing Instruction and Study to Improve Student Learning (Pashler and others, NCER 2007-2004) recommends spacing reviews out over time, alternating worked examples with problems students solve on their own, pairing pictures with words, and using quizzes to bring key content back. The Earth & Space Ladder is built around those ideas.
Try it in the Science Lab
Simulations to play with alongside the lessons.
The other ladders
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- Logic LadderClear thinking, from arguments and fallacies to syllogisms, truth tables and formal proofs, grade 7 to college. 3 courses.
- Etiquette LadderManners as kindness made into habits: please and thank you, the table, conversation, notes and hard moments, age 4 to adult. 3 courses.
- Egyptology LadderAncient Egypt from the Nile and the pyramids to reading hieroglyphs: history, Middle Egyptian, religion and art, and archaeology, age 8 to college. 6 courses.
- Ancient Scripts LadderHow ancient scripts work and how they were read again, beginning with Linear A and Linear B of the Bronze Age Aegean, high school to college. 1 courses.
- Vocabulary LadderOne thousand advanced words, each with a picture and a memory hook, plus the Greek and Latin roots that unlock them, grade 6 to adult. 2 courses.
All the ladders share one progress: XP, your streak and your reviews.
Your progress is saved in this browser
No account needed. To move to another device, or to keep a backup, copy your save code and paste it in on the other device.
See your progress · The site's My Progress page backs up everything at once.