| A | B |
|---|
| rotation | spinning of Earth on its axis |
| revolution | movement of Earth around sun |
| orbit | path Earth travels around sun |
| astronomy | study of planets, stars, and space |
| 365.25 days | Earth's period of revolution |
| 24 hours | Earth's period of rotation |
| 23.5 degrees | Earth's tilt on its axis |
| Universal gravitation | Newton's law that all objects attract all others |
| phases | different shapes of the moon seen from Earth |
| solar eclipse | moon casting a shadow on Earth |
| lunar eclipse | Earth casting a shadow on the moon |
| umbra | darker, inner part of shadow |
| penumbra | lighter, outer part of shadow |
| eight | number of lunar phases |
| weight | determined by the force of gravity |
| mass | amount of matter in an object |
| Newton | unit of weight named for scientist |
| inertia | tendency of an object to resist change in motion |
| 1st law of motion | object stay at rest/stay in motion unless outside force |
| axis | Earth's imaginary line from pole to pole |
| equinox | 2 days a year with equal light and dark |
| solstice | 2 days/year with sun farthest from equator |
| spring tide | sun, moon, and Earth all line up to make higher tide |
| neap tide | moon and sun at right angles to Earth/lower high tide |
| tides | caused by moon's gravitational pull |
| 29.5 days | moon's period of revolution |
| equal | moon's period of rotation and revolution |
