What is an orbit?
An orbit is the path of a body moving under another body’s gravity.
How it works and key principles
Why it happens: An object with sideways velocity continually changes direction under gravity; with sufficient speed it moves around a central body. Orbits are often elliptical, with speed changing along the path. A satellite’s trajectory depends on velocity and direction as well as altitude.
Evidence, examples and limits
Uses and limits: Communications, navigation and Earth observation satellites use different orbits. Thin atmospheric drag can gradually lower a low Earth orbit. Gravity still acts on astronauts; their apparent weightlessness results from continuous free fall.
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