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unit 4
The Earth-Moon-Sun System
| Term | Definition |
|---|---|
| rotation | The spin of a body on its axis |
| day | The time required for Earth to rotate once on its axis |
| revolution | The motion of a body that travels around another body in space; one complete trip along an orbit |
| year | The time required for the Earth to orbit once around the sun |
| season | A division of the year that is characterized by recurring weather conditions and determined by both Earth's tilt relative to the sun and Earth's position in its orbit around the sun. |
| equinox | The moment when the sun appears to cross the celestial equator. |
| solstice | The point at which the sun is far north or as far south of the equator as possible. |
| satellite | A natural or artificial body that revolves around a planet |
| gravity | A force of attraction between objects that is due to their masses |
| lunar phases | The difference appearances of the moon from Earth throughout the month. |
| eclipse | An event in which the shadow of one celestial body falls on another. |
| umbra | A shadow that blocks sunlight, such as the conical section in the shadow of the Earth or the moon |
| penumbra | The outer part of a shadow cast by Earth or the moon in which sunlight is practically blocked. |
| tide | The periodic rise and fall of the water level in the oceans and other large bodies of water |
| tidal range | The difference in levels of ocean water at high tide and low tide. |
| spring tide | A tide of increased range that occurs two times a month, at the new and full moons. |
| neap tide | A tide of minimum range that occurs during the first and third quarters of the moon. |