| A | B |
|---|
| fission theory | moon was once part of the earth and somehow separated from us |
| Pacific basin | most likely spot for part-removal of Moon |
| capture theory | moon was formed somewhere else and captured by Earth |
| twin theory | Moon and Earth condensed together from original solar system |
| collision theory | something the size of Mars struck Earth, ejecting large volumes of matter-eventually forms Moon |
| new moon | The Moon is not illuminated by direct sunlight |
| waxing crescent | The visible Moon is partly but less than one-half illuminated by direct sunlight while the illuminated part is increasing. |
| waning crescent | The Moon is partly but less than one-half illuminated by direct sunlight while the illuminated part is decreasing. |
| waxing gibbous | The Moon is more than one-half but not fully illuminated by direct sunlight while the illuminated part is increasing. |
| waning gibbous | The Moon is less than fully but more than one-half illuminated by direct sunlight while the illuminated part is decreasing. |
| full moon | The visible Moon is fully illuminated by direct sunlight. |
| 1st quarter | One-half of the Moon appears illuminated by direct sunlight while the illuminated part is increasing. |
| last quarter | One-half of the Moon appears illuminated by direct sunlight while the illuminated part is decreasing. |
