Gravity - A force of attraction between objects that is due to their masses., Weight - The effect of gravity on a mass, Orbit - a circular path around another object, Revolution - The movement of an object around another object, Year - the time required for the Earth to orbit once around the sun 365 1/4 days, Rotation - The spinning of Earth on its axis, Day - the time required for Earth to rotate once on its axis 24 hours, Axis - an imaginary line that runs straight through the planet from the North Pole to the South Pole, Daytime - The side of the Earth that has rotated toward the Sun., Night - The side of the Earth that has rotated away from the Sun., Astronomical Unit - the average distance between the Sun and the Earth; used to measure things inside our solar system, Light year - the distance light can travel in one year; used to measure very large distances outside of our solar system,

Astronomy Basics

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