The planets going around stars have gravity on them, but that gravity is countered by the motions of the planets, and that is what keeps them in perpetual orbit until the stars get bigger and suck the planets in. The sun will eventually turn into a red giant and suck in Earth and the other planets.
Because of the big bang, the universe is still spreading outward. For a while, astronomers thought that the universe would eventually collapse due to gravity. But now they think the spread out force is enough to get the universe scattered enough to keep enough force to never collapse. That is disappointing because I used to think the big bang would happen again the same way it did last time and the entire course of the universe would happen the same way again, so we would live our lives an ininite number of times and already have lived them an infinite number of times. So it looks like scientists made an error that made us go from believing in an infinite number of lives to seeing the oncoming of eternal death. Dammit.
Why do you troll more than you discuss? Did you join this site just to be insulting? They don't usually teach this stuff in high school physics any way. This is astronomy, which is an elective if anything in high school.
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