From motion to orbits

Start with motion and forces, then follow gravity out to the planets. Each concept comes before the concepts that build on it, and the simulation, 3D explorer and activities sit next to the idea they let you try.

1. Step 1Concept

   Motion

   The change in an object's position over time relative to a reference frame. Kinematics describes motion using position, velocity (the rate of change of position) and acceleration (the rate of change of velocity), without yet asking what causes it.

2. Step 2Concept

   Forces

   A push or pull interaction between two objects, capable of changing an object's velocity. Newton's three laws of motion describe how forces and motion relate: a body keeps its state of motion unless acted on by a net force (first law), net force equals mass times acceleration, F = ma (second law), and forces between two bodies are equal and opposite (third law).

3. Step 3Hands-on activity

   Paper Helicopter Drop Timing

   A hands-on activity with 5 materials and 6 steps.

4. Step 4Concept

   Gravity

   The attractive force between any two masses. Newton's law of universal gravitation describes it as proportional to the product of the two masses and inversely proportional to the square of the distance between them. Near Earth's surface this produces a roughly constant downward acceleration of about 9.8 m/s^2 on falling objects.

5. Step 5Simulation

   Gravity & Orbital Motion

   Explore Newtonian gravity and circular-orbit mechanics interactively — adjust central body mass, orbiting body mass and orbital radius and see the real gravitational force, orbital velocity and orbital period recompute live.

6. Step 6Concept

   Stars

   A massive, luminous sphere of plasma held together by its own gravity, generating energy in its core through nuclear fusion — mainly the fusion of hydrogen into helium. Stars form from collapsing clouds of gas and dust, shine for millions to billions of years depending on their mass, and eventually exhaust their nuclear fuel, ending their lives as white dwarfs, neutron stars, or black holes depending on their initial mass.

7. Step 7Concept

   Solar System

   The Sun and everything gravitationally bound to it: eight planets, their moons, dwarf planets such as Pluto, and countless smaller bodies including asteroids and comets. The Sun's gravity holds the whole system together and keeps the planets in elliptical orbits described by Kepler's laws of planetary motion.

8. Step 83D explorer

   Solar System Explorer

   Explore the Sun and eight planets in an interactive 3D scene built on real orbital mechanics and NASA planetary data, with a guided planetary tour and adjustable distance scale.

9. Step 9Hands-on activity

   Scale Solar System Walk

   A hands-on activity with 4 materials and 5 steps.

All learning pathways