| A | B |
|---|
| gravity | The force that keeps the planets and moons in orbit. |
| mass | The amount of matter in a body. |
| weight | The gravitational force on a body. |
| G-forces | How we measure gravitational force on the earth |
| inertia | The tendency of an object to resist change. |
| ellipse | The shape of the Earth's orbit, like a slightly flattened circle. |
| aphelion | When the earth is farthest away from the sun: January 2nd. |
| perihelion | When the earth is closest to the sun: July 3rd. |
| velocity | The speed of something. |
| revolution | The action of a body going around in orbit. |
| orbit | The path a body takes by circling another. |
| Newton's first law | An object at rest stays at rest, an object in motion stays in motion unless acted upon by an outside force. |
