| 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 day 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 |
