| 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. |
| LATITUDE | The distance north or south from the equator, measured in degrees. |
| 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. |
| SPRING EQUINOX | The day of the year that marks the beginning of spring in the Northern Hemisphere. |
| FALL 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. |
| UMBRA | The darkest part of a shadow. |
| 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. |
| TIDE | The daily rise and fall of Earth's waters on shores. |
| 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. |
| CRATER | A round pit on the moon's or other surface, created by a force of impact. |
| MARIA | Dark, flat regions on the moon's surface. |
| LAW OF UNIVERSAL GRAVITATION | The law that states all objects attract all other objects. |
| KEPLER'S FIRST LAW OF PLANETARY MOTION | The law that states that planets travel in elliptical orbits. |
| KEPLER'S SECOND LAW OF PLANETARY MOTION | The law that states that the closer a planet is to the sun, the faster it revolves.. |
| KEPLER'S THIRD LAW OF PLANETARY MOTION | The law that states that a planets average distance to the sun can be used to calculate how long that planet will take to revolve, and vice verse. |
| MASS | The amount of matter in an object. |
| INERTIA | The tendency of an object to resist a change in motion. |
| WEIGHT | The pull of gravity on an object. |
| SPRING TIDE | The tide with the greatest differences between high and low tide. It occurs during a full or new moon. |
| NEAP TIDE | The tide with the least difference between the high and low tide. It occurs during a first or third quarter moon. |
| WINTER SOLSTICE | The shortest day of the year, when the noon sun appears the lowest in the sky. |
| SUMMER SOLSTICE | The longest day of the year, when the noon sun appears the highest in the sky. |
