Physics and maths that take you to the stars
Free interactive lessons for ages 9 and up, from first fractions to A‑level physics. Launch a satellite, bend a beam of light, tune a wave: every idea here is something you can try for yourself.
A high elliptical orbit
Faster than circular speed, so it swings out to an apogee of 8,431 km before gravity pulls it back in.
Uses real Earth gravity (R = 6,370 km, GM = 3.986 × 10⁵ km³/s²): a satellite released sideways 2,000 km up, where circular speed is 6.9 km/s and escape speed is 9.8 km/s. Time is sped up at least 700 times. Launch footage is from NASA (Artemis I and II); Stella Academy is not affiliated with NASA.
Stella’s journey
Five missions take you from your first number skills to reading the light of distant stars. Each one is a short run of lessons, and the star marks where you are.
Or pick by level
Pick the stage that suits you, whatever your age. Each lesson is matched to the national curriculum for England, not to one exam board, so check your own specification if you are revising for an exam.
Key stage 4: the core ideas of school physics and maths. 9 lessons.
- Physics15 minRefraction and Snell's LawWhy light bends when it enters glass or water, and how a prism splits it into colours.
- Physics10 minGears and Gear RatiosHow gears trade speed for turning force, and how to work out a gear ratio.
- Physics10 minOhm's Law: Voltage, Current and ResistanceHow voltage, current and resistance are linked in a circuit.
- Physics15 minWaves: Frequency, Wavelength and SpeedHow the speed, frequency and wavelength of a wave are linked.
- Maths15 minTrigonometry in Right-Angled TrianglesFind missing sides and angles using sine, cosine and tangent.
- Maths15 minVectors: Magnitude and DirectionAdd vectors, split them into components and find their size and direction.
- Maths15 minProbabilityWork out how likely events are, alone and combined, using spacecraft reliability as the example.
- Physics15 minMomentum and CollisionsUse conservation of momentum to work out what happens in collisions, and see how a rocket speeds up.
- Physics15 minConverting UnitsUse prefixes and conversion factors to change the unit without changing the quantity.
How a lesson works
Play with the model
Move a slider and see what changes. You get a feel for the idea before any equations.
Follow a worked example
One question solved a line at a time, with every symbol in the formula explained.
Answer the practice questions
Try them yourself, then reveal a hint or the answer to check your working.
Free to use, not free to run
Help Stella Academy pay for itself
All 31 lessons, interactive models and step-by-step quizzes on Stella Academy are free to use in your browser. Keeping the servers, video delivery and development going costs real money and time: if the lessons help you, your child or your class, please chip in on Ko-fi or help us review a mission.
Interactive simulators and worked examples across five space missions.
Adaptive step-by-step questions with fresh numbers every time.
Every lesson quotes the Department for Education statements it covers across KS2, KS3, GCSE and A-level.
Need a break? Look through the NASA image gallery.