| A | B |
|---|
| Orbit | path of a planet around the Sun |
| Astronomy | The study of the moon, stars, and other objects in space. |
| Axis | an imaginary line around which an object spins |
| Rotation | spinning about an axis |
| Revolution | The movement of an object around another. |
| Calendar | A system of arganizing time that that defines the beginning and end of a year. |
| Solstice | The two days of the year when the sun reaches its farthest distance north or south of the equator. |
| Equinox | The two days each year on which neither hemisphere is pointed towards or away from the sun. |
| Force | A push or a pull on an object. |
| Gravity | The attractive force between two objects. |
| Mass | The amount of matter in an object. |
| Weight | The measure of the force of gravity on an object. |
| Inertia | The tendency of an object to resist a change in motion. |
| Phases | One of the different apparent shapes fo the moon as seen from Earth. |
| Eclipse | The partial or total blocking of one object by another in space. |
| Umbra | The darkest part of a shadow. |
| Penumbra | The part of a shadow surrounding the darkest part. |
| Tide | The periodic rise and fall of the water level in the ocean |
| Neap Tide | The tide with the least difference between consecutive low and high tides. |
| Spring Tide | The tide with the greatest difference between consecutive low and high tides. |
