perturbation theory
Quick Summary
Perturbation theory is a mathematical method used in physics to find approximate solutions to complex problems by starting with a simpler, known solution and then making small corrections for additional factors. It's particularly useful when a problem differs only slightly from one that can be solved exactly.12
In celestial mechanics, perturbation theory helps describe the motion of objects like planets or satellites. While the ideal two-body problem results in fixed orbital parameters, real-world gravitational influences from other bodies cause these parameters to change slowly over time. These changes are called perturbations.3
Perturbation theory is also fundamental in quantum electrodynamics (QED), a theory describing how charged particles interact with the electromagnetic field. Because the fine-structure constant is small, higher-order contributions to calculations become progressively smaller, making QED a successful example of a perturbation theory.4
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