| Term | Definition |
|---|---|
| astronomy | The study of the moon, stars, and other objects in space. |
| axis | An imaginary line the passes through earth's center and the north and south poles, about which earth rotates. |
| rotation | The spinning of a planet on its axis. |
| orbit | The path of an object as it revolves around another object in space. |
| calendar | A system of organizing time that defines the beginning, length, and divisions of the year. |
| solstice | The two days of the year on which the sun reaches its greatest distance north or south of the equator. |
| Equinox | The two days of the year on which neither hemisphere is tilted toward or away from the sun. |
| revolution | The movement of an object around another object. |
| force | a push or pull. |
| gravity | Attracts all objects toward each other. |
| Law of Universal Gravitation | Every object in the universe attracts every other object. |
| mass | Amount of matter in an object. |
| weight | Force of gravity on an object. |
| inertia | Tendency of an object to resist change. |
| Newtons First Law of Motion | 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. |
| Phases | The different shapes of the moon you see from earth |
| Eclipse | When an object in space comes between the sun and a third object, it casts a shadow on that object. |
| Solar Eclipse | Occurs when a new moon blocks your view of the sun. |
| Umbra | The very darkest part of the moon's shadow. |
| Penumbra | The largest part of the shadow. |
| Lunar Eclipse | Occurs at a full moon when earth is directly between the moon and the sun. |
| Tides | The rise and fall of ocean water that occurs every 12.5 hours or so. |
| Spring Tide | The tide with the greatest difference between consecutive low and high tides. |
| Neap Tide | The tide with the least difference between consecutive low and high tides. |
| Telescope | A device built to observe distant objects by making them appear closer. |
| Maria | Dark flat areas on the moon's surface formed from huge ancient lava flows. |
| Craters | A large round pit caused by the impact of a meteoroid. |
| Meteoroids | A chunk of rock or dust in space. |
