Newton's Gravitational Force
Every mass attracts every other mass. The bigger the mass, the stronger the pull. The farther apart, the weaker the pull. F = G(m₁m₂)/r² — double the distance, gravity becomes four times weaker.
Why Orbits Don't Fall
A satellite in orbit is actually falling toward Earth constantly. But it's moving sideways so fast that it keeps missing Earth — it falls around the planet. If you could throw a ball horizontally at 28,000 km/h, it would orbit Earth forever.
Escape Velocity
To escape Earth's gravity completely, you need about 11.2 km/s (25,000 mph). This is escape velocity. The Moon's smaller gravity means lower escape velocity — 2.4 km/s. That's why Apollo missions could leave the Moon easily.
Tides and Gravity
Ocean tides happen because the Moon's gravity pulls harder on the near side of Earth than the far side. The Sun also contributes — during full and new moons, when Sun and Moon align, we get spring tides.