| A | B |
|---|
| Astronomy | The study of the moon, stars and other objects in space. |
| Axis | An imaginary line that passes through Earth's center 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 N or S latitude. |
| Equinox | The two days of the year on which neither hemisphere is tilted toward or away from the sun (equal day, equal night). |
| Eclipse | The partial or total blocking of one object by another. |
| Umbra | The darkest part of a shadow. |
| Penumbra | The part of a shadow surrounding the darkest part. |
| Tide | The rise and fall of Earth's water due to the moon's gravitational pull. |
| Satellite | Any object that revolves around another object in space. |
