Orbital Mechanics for the Young Science Fiction Villain

Orbits occur when an object is moving fast enough, but not too fast, relative to a central body that gravity pulls its trajectory into an ellipse . Too slow, and gravity pulls the mass into a collision course. Too much velocity behind the mass, and it will overcome the acceleration (pull) of gravity to continue onward, uninterrupted, "To infinity and beyond!". Something to keep in mind when talking about orbital mechanics is that Sir Isaac Newton invented calculus just so he could talk about it intelligently with math.