Orrery
The solar system in real time. Travel through time, change the speed, switch to true scale and compare any two worlds.
Interactive tools
Play first, formulas later. Every tool works on a phone, with a keyboard, and comes with a table of the same data.
ESO/S. Guisard (www.eso.org/~sguisard) (CC BY 4.0)
Orbit Sandbox
Change an orbit's shape and watch its speed change. See Kepler's second and third laws in action.
Scale Walk
Scroll from the Sun to Neptune at true scale, with light-travel time markers along the way.
Delta-v Map
How much change in speed it takes to move between Earth, orbit, the Moon, Mars and the asteroids.
Newton's Cannon
Fire a cannonball faster and faster from a mountain top until it orbits, then escapes.
Seasons Explorer
Earth's tilt, the Sun's height and the length of the day for any place and date.
Moon Phases and Eclipses
Move the Moon around the Earth and see its phase from Earth, and when eclipses can happen.
Night Sky and Light Pollution
A real star catalogue. Drag the light pollution slider and watch the stars disappear.
Tools and lessons use simplified models for learning only. They must not be used for navigation, mission planning or any operational decision. Certificates are free and non-accredited. Read the educational content disclaimer