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Orbital mechanics is a core discipline within space-mission design and control. Celestial mechanics treats more broadly the orbital dynamics of systems under the influence of gravity , including both spacecraft and natural astronomical bodies such as star systems , planets , moons , and comets .
Given the different Sun incidence in different positions in the orbit, it is necessary to define a standard point of the orbit of the planet, to define the planet position in the orbit at each moment of the year w.r.t such point; this point is called with several names: vernal equinox, spring equinox, March equinox, all equivalent, and named considering northern hemisphere seasons.
Lense–Thirring precession, a general-relativistic correction accounting for the frame dragging by the Kerr metric of curved space near a large rotating mass. The Schwarzschild geodesics (sometimes Schwarzschild precession) is used in the prediction of the anomalous perihelion precession of the planets, most notably for the accurate prediction ...
The subject is based upon a three-dimensional Euclidean space with fixed axes, called a frame of reference. The point of concurrency of the three axes is known as the origin of the particular space. [3] Classical mechanics utilises many equations—as well as other mathematical concepts—which relate various physical quantities to one another.
Despite being correct in saying that the planets revolved around the Sun, Copernicus was incorrect in defining their orbits. Introducing physical explanations for movement in space beyond just geometry, Kepler correctly defined the orbit of planets as follows: [1] [2] [5]: 53–54 The planetary orbit is not a circle with epicycles, but an ellipse.
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The Earth rotation angle (ERA) measures the rotation of the Earth from an origin on the celestial equator, the Celestial Intermediate Origin, also termed the Celestial Ephemeris Origin, [9] that has no instantaneous motion along the equator; it was originally referred to as the non-rotating origin. This point is very close to the equinox of J2000.
By ANDREW TAVANI Signs of the changing seasons are everywhere right now: the ever decreasing daylight; the preemptive Christmas commercials on TV; and, of course, the most ubiquitous and pleasant ...