Gravity and Tides
Tides and planetary orbits are caused by the pull of gravity.
Effects of Mass and Distance on Gravitational Force
- The more massive an object, the greater it’s gravitational pull.
- The closer the distance between objects, the greater the gravitational pull
- The gravitational pull between the Sun and the planets and between Earth and its Moon cause distinct motions between and among these bodies
- The Sun’s gravitational attraction, along with the planet’s inertia (continual forward motion), keeps the planets moving in elliptical orbits (Earth’s orbit is slightly oval) and determines how fast they orbit.
- Planets nearer the Sun move/orbit faster than planets farther from the Sun because the gravitational attraction is greater.
- When a planet is farther from the Sun, the gravitational attraction between them decreases and the planet moves/orbits slower.
- Since the Moon is closer to Earth than the Sun (distance), the Moon has the greatest pulling effect on tides, the rise and fall of Earth’s waters.
- The Sun also pulls on Earth and
- can combine its force with the Moon causing even higher tides, spring tides
- or can be a right angles, pulling against the Moon’s pull, causing very little tidal change, neap tides.