| A | B |
|---|
| ASTRONOMY | The study of the moon, stars, and the objects in space. |
| AXIS | An imaginary line that passes through Earth's center and the North and South poles, about which Earth rotates. |
| ROTATION | The spinning motion of a planet about its axis. |
| REVOLUTION | The movement of an object around another object. |
| ORBIT | The path of an object as it revolves around another object in space. |
| SOLSTICE | The two days of the year on which the noon sun is directly overhead at either 23.5° South or 23.5° North. |
| EQUINOX | The two days of the year on which neither hemisphere is tilted toward or away from the sun. |
| VERNAL EQUINOX | The day of the year that marks the beginning of spring in the Northern Hemisphere. |
| AUTUMNAL EQUINOX | The day of the year that marks the beginning of fall in the Northern Hemisphere. |
| PHASE | One of the different shapes of the moon as seen from Earth. |
| ECLIPSE | The partial or total blocking of one object by another. |
| SOLAR ECLIPSE | The blocking of sunlight to Earth that occurs when the moon is between the sun and Earth. |
| PENUMBRA | The part of a shadow surrounding the darkest part. |
| LUNAR ECLIPSE | The blocking of sunlight to the moon that occurs when Earth is directly between the sun and moon. |
| GRAVITY | The attractive force between two objects; its magnitude depends on their masses and the distance between them. |
| SATELLITE | Any object that revolves around another object in space. |
| TELESCOPE | A device built to study distant objects by making them appear closer. |
| CRATER | A round pit on the moon's or other surface, created by a force of impact. |
