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Defend Earth from alien invaders
The science that studies the universe and deals with the properties of objects in space and the laws under which the universe operates
The thought that the stars and the other planets and the sun orbit around the earth
A model that proposed the earth and the planets revolve around the sun
The irregular movement the planets make
Sates that every body in the universe attracts to every other body with a force that is directly proportional to their mass and inversely proportional to the square of the distance between their centers of mass
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