Term | Definition |
law of universal gravitation | every object in the universe attracts every other object, depending on their masses and distances from one another |
solstice | the two days of the year in which the sun's most direct rays reach farthest north or farthest south |
equinox | the two days of the year when day and night are almost the same length everywhere on earth |
crescent | the moon phase in which less than half of the moon's sunlit side is visible |
gibbous | the moon phase in which more than half, but not all, of the moon's sunlit side is visible |
wax | to grow |
wane | to shrink |
lunar eclipse | an event that occurs when Earth passes directly between the sun and the moon, causing the moon to be temporarily "eclipsed" or hidden |
solar eclipse | an event that occurs when the moon passes directly between the sun and Earth, causing the sun to be temporarily "eclipsed" or hidden |
tide | the periodic rising and falling of the surface level of ocean water |
spring tide | a condition of the greatest difference between low and high tides |
neap tide | a condition of the LEAST difference between low and high tides |
revolution | the movement of going around an object |
rotation | the movement of spinning on an axis |
mass | a measure of how much matter is within an object; greater the mass, the greater the gravity of an object |
axis | an imaginary line that Earth spins on at a 23.5 degree angle |