| A | B |
|---|
| astronomy | the study of the moon, stars, and other objects in space |
| axis | an imaginary line that passes through Earth's center and the poles |
| rotation | Earth's spinning on its axis causing day and night |
| revolution | the movement of one object around another |
| orbit | Earth's path as it revolves around the sun |
| latitude | a measurement of distance from the equator, expressed in degrees north or south |
| solstice | the two days of the year on which the noon sun is directly overhead at either 23.5 degrees north or south |
| equinox | the two days out of the year on which neither hemisphere is tilted toward or away from the sun |
| vernal equinox | occurs around March 21 and marks the beginning of spring in the Northern Hemisphere |
| autumnal equinox | occurs around September 23 and marks the beginning of fall in the Northern Hemisphere |
| phase | the different shapes of the moon you see from Earth |
| eclipse | occurs when an object in space comes between the sun and a third object and casts a shadow on that object |
| solar eclipse | occurs when the moon passes between Earth and sun, blocking the sunlight from reaching Earth |
| umbra | the darkest part of the moon's shadow during a total eclipse |
| penumbra | a larger, less dark part of the shadow |
| lunar eclipse | occurs at a full moon when Earth is directly between the moon and sun |
| tide | the rise and fall of water on Earth caused by how much the moon pulls on different parts of Earth |
| gravity | the attractive force between two objects |
| spring tide | a tide with the greatest difference between high and low tide occuring at new and full moons |
| neap tide | a tide with the least difference between low and high tide occuring at first and last quarter moons |
| satellite | any natural or artificial object that revolves around an object in space |
| geosynchronous orbit | revolving at the same rate that Earth rotates |
| telescope | optical instrument that makes distant objects appear closer |
| crater | round pits on the moon's surface caused by meteoroid impacts |
| maria | dark, flat areas on the moon's surface |
