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2

I think your problem is just a matter of terminology. Almost all of the orbits you hear about are elliptical. Some are almost exactly circular, but that counts as a special case of elliptical. Orbits like that keep going round and round, and stay within a certain distance of the primary. You might have the impression that's part of the meaning of "orbit". ...


4

This relates to the concept of escape velocity, which is the speed needed to escape an object's gravity well. Even though gravity has an infinite reach, the fact that its force reduces quadratically with distance means that it only takes a finite amount of energy to climb out of a planet's gravity well. For some fixed energy cost, you can get arbitrarily far ...


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