What is gravity?

Gravity: F = G m₁ m₂ ÷ r². Every mass pulls on every other mass. The pull grows with both masses and falls with the square of the distance, so it is tiny between everyday things but big enough to hold you to the Earth and the Moon in its orbit.

Read how it works: What is gravity? · The history of gravity · More boxes on Glassbox

Chapters in this interactive model

1. Every mass pulls on every other mass: Double the mass, double the pull. Double the distance, a quarter of the pull.
2. Falling, weight, and why astronauts float: Weight depends on where you are. Floating in orbit is falling, all the time.
3. Orbits, satellites and the tides: Falling round and round, and a Moon that stretches the seas.
4. Gravity at home: taps, blood, bikes and clocks: The same pull fills your bucket, strains your heart, rolls your bike and keeps time.
5. Curved spacetime, black holes, and two myths: Newton’s law works beautifully, until clocks, light and black holes get involved.