| A | B |
|---|
| satellite | A body that orbits a planet. |
| comet | A cold mixture of dust and ice that gives up a long trail of light as it approaches the sun. |
| planet | An object that orbits the sun, is large enough to have become rounded by its own gravity, and has cleared the area of its orbit |
| star | A giant ball of hot gas, mainly composed of hydrogen and helium. |
| meteor | A streak of light produced when a small object burns up entering Earth's atmosphere. |
| constellation | A pattern or group of stars that people imagined to represent a figure, animal, or object. |
| axis | The imaginary line that passes through Earth's center and the North and South poles. |
| calendar | A system of organizing time that defines the beginning, length, and divisions of a year. |
| rotation | The spinning of Earth on its axis. |
| solstice | The day when the sun either appears farthest north or south of the equator. |
| revolution | The movement of one object around another. |
| equinox | Means "equal night". Halfway between the soltices, when neither hemisphere is tilted |
| orbit | Earth's path around the sun. |
| force | A push or pull. |
| mass | The amount of matter in an object. |
| gravity | The force in our universe that attracts all objects toward each other. |
| weight | The measure of the force of an object. |
| law of the universal gravitation | This law states that every object in the universe attracts every other object. |
| inertia | The tendency of an object to resist change in motion. |
| Newton's first law of motion | This law states that an object at rest will stay at rest and an object in motion will stay in motion with a constant speed and direction unless acted on by a force. |
