A good place to start
Why do we slip on ice?
From force to friction: the physics inside a single step
Walking is really a little shoving match with the ground, and you win it.
- 4 steps
- 1 h 6 min
- 7 simulations
Journeys
Start with a question.
Each journey grows out of a single question most of us have wondered about at some point, and leads through a few short lessons. Follow the steps in order and by the end you'll be able to answer that question in your own words.
You can try the simulation in every step without an account. If you want to save your place, a free account is all you need. There are currently 12 journeys with 53 steps in total.
- Physics
- Probability
Does luck really exist?
One throw is a surprise; a thousand throws make a rule.
- 5 steps
- 1 h 25 min
- 6 simulations
- Light
Why is the sky blue?
The Sun sends out white light; it's the air that scatters the blue across the sky.
- 4 steps
- 1 h 6 min
- 7 simulations
- Space
How small are we in the universe?
If the Sun were a ball one metre across, the Earth would be a bead nine millimetres wide.
- 5 steps
- 1 h 23 min
- 7 simulations
- Electricity
How does electricity flow?
Electricity flows only when it finds a way back.
- 4 steps
- 1 h 6 min
- 4 simulations
- Maths
How do you divide a pizza fairly?
Fair sharing starts with equal parts.
- 4 steps
- 1 h 10 min
- 4 simulations
- Matter
Why does ice float on water?
Most substances shrink when they freeze. Water expands.
- 4 steps
- 1 h 14 min
- 4 simulations
- Music
Why does music sound pleasant?
Your ear listens not to frequencies but to the ratios between them.
- 4 steps
- 1 h 8 min
- 7 simulations
- Art
How does a picture gain depth?
On a flat surface, depth begins where a few straight lines meet in just the right place.
- 4 steps
- 1 h 9 min
- 7 simulations
- Nature
How does a seed become a plant?
Most of a tree's mass comes not from the soil but from the air.
- 5 steps
- 1 h 21 min
- 10 simulations
- Kitchen
Why is the kitchen a laboratory?
Every recipe is an experiment you can eat.
- 5 steps
- 1 h 26 min
- 9 simulations
- History
How did we measure the Earth?
The shadow of a stick can tell you the size of a planet.
- 5 steps
- 1 h 27 min
- 9 simulations