| Term | Definition |
|---|---|
| Sphere | A round, three dimensional object whose surface is the same distance from the center at all points ; Earth is a sphere that bulges somewhat at the equator and is slightly flattened at the poles |
| Axis | Imaginary line that cuts through the center of Earth and around which Earth spins |
| Rotation | Spinning of Earth on its imaginary axis, which takes about 24 hours to complete and causes day and night to occur |
| Revolution | Earth's yearlong elliptical orbit around the sun |
| Ellipse | Elongated, closed curve that describes Earth's yearlong orbit orbit around the sun |
| Solstice | twice yearly point at which the sun reaches its greatest distance north or south of the equator |
| Equinox | Twice yearly time-each spring and fall when the sun is directly over the equator and the number of daytime light and nighttime hours are equal worldwide |
| Moon Phase | Change in appearance of the moon as viewed from the Earth due to the relative positions of the moon, Earth and Sun |
| New Moon | Moon phase that occurs when the moon is between the Earth and the sun, at which point the moon cannot be seen because its lighted half is facing the sun and its dark side faces Earth. |
| Waxing | describes phases following a new moon, as more of the moons lighted side becomes visible |
| Full Moon | Phase that occurs when all of the moon's surface facing Earth reflects light |
| Waning | Describes phases that occur after a full moon, as the visible lighted side of the moon grows smaller |
| Solar Eclipse | Occurs when the Moon passes directly between the Sun and Earth and casts a shadow over part of Earth |
| Lunar Eclipse | Occurs when Earth's shadow falls on the moon. |
| Maria | Dark-Colored, relatively flat regions of the Moon formed when ancient lava reached the surface and filled craters on the Moon's Surface |
| Impact Basin | a hollow left on the surface of the moon caused by an object striking its surface |
