| A | B |
|---|
| tide | the periodic rise and fall of the water level in the oceans and other large bodies of water |
| neap tide | a tide of minimum range that occurs during the first and third quarters of the moon |
| tidal range | the difference of 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 |
| solar system | the sun and all of the planets and other bodies that travel around it |
| nebula | a large cloud of gas and dust in interstellar space; a region in space where stars are born |
| universe | space and all the matter and energy in it |
| planet | a relatively large spherical body that orbits a star |
| galaxy | a collection of stars, dust, and gas bound together by gravity |
| star | a large celestial body that is composed of gas and that emits light; the sun is a typical star |
| light year | the distance that light travels in one year; about 9.46 trillion kilometers |
