Orbital elements are the parameters required to uniquely identify a specific orbit. In celestial mechanics these elements are generally considered in classical two-body systems, where a Kepler orbit is used (derived from Newton's laws of motion and Newton's law of universal gravitation). There are many different ways to mathematically describe the same orbit, but certain schemes each consisting of a set of six parameters are commonly used in astronomy and orbital mechanics.
A real orbit (and its elements) changes over time due to gravitational perturbations by other objects and the effects of relativity. A Keplerian orbit is merely an idealized, mathematical approximation at a particular time.
Read more about Orbital Elements: Keplerian Elements, Required Parameters, Alternative Parametrizations, Orbit Prediction, Perturbations and Elemental Variance, Two-line Elements
Famous quotes containing the word elements:
“Nature confounds her summer distinctions at this season. The heavens seem to be nearer the earth. The elements are less reserved and distinct. Water turns to ice, rain to snow. The day is but a Scandinavian night. The winter is an arctic summer.”
—Henry David Thoreau (1817–1862)