Why do planetary bodies rotates around axis. Which force is causing this rotation and why. Also are the stars rotating as well and do planets orbit them because they are rotating or is there some other reason.
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it’s a collection of particles that all had their own energies and directions of motions before they collided and stuck together. it’s overwhelming unlikely that gazillions of them forming a planetary body all coalesce in a perfect way that no net rotation forms as a result. like two cue balls crashing and coming to a complete stop with no glancing upon contact, except imagine a gazillion of them. sitting on a swivel chair, stretch out your arms and see if you can pull them in quickly without ending up with some rotation in the chair.
after the last particle joins the system there is no force that keeps it rotating per se. any forces that can be observed in that rotating system does not result in any movement in the direction of that force. so no energy is exchanged, no work is done, thus that rotation continues forever.
I say per se because there is a force that exists holding those particles together and it is a combination of electric and gravitational forces. if for any reason those are overcome, then the planet breaks up and all particles leave in straight lines away from what was once the planet. but of course that means there is no planet anymore which is a different question.
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