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The average distance between Neptune and the Sun is 4.5 billion km (about 30.1 astronomical units (AU), the mean distance from the Earth to the Sun), and it completes an orbit on average every 164.79 years, subject to a variability of around ±0.1 years. The perihelion distance is 29.81 AU, and the aphelion distance is 30.33 AU.
Most of the material orbits and rotates in one direction. This uniformity of motion is due to the collapse of a gas cloud. [1] The nature of the collapse is explained by conservation of angular momentum. In 2010 the discovery of several hot Jupiters with backward orbits called into question the theories about the formation of planetary systems. [2]
Carl Runge and Wilhelm Lenz much later identified a symmetry principle in the phase space of planetary motion (the orthogonal group O(4) acting) which accounts for the first and third laws in the case of Newtonian gravitation, as conservation of angular momentum does via rotational symmetry for the second law. [22]
The speed of gravitational waves in the general theory of relativity is equal to the speed of light in vacuum, c. [3] Within the theory of special relativity, the constant c is not only about light; instead it is the highest possible speed for any interaction in nature.
The observation that the solar system is old enough allowed him to put a lower limit on the speed of gravity that turned out to be many orders of magnitude faster than the speed of light. [5] [7] Laplace's estimate for the speed of gravity is not correct in a field theory which respects the principle of relativity.
In gravitationally bound systems, the orbital speed of an astronomical body or object (e.g. planet, moon, artificial satellite, spacecraft, or star) is the speed at which it orbits around either the barycenter (the combined center of mass) or, if one body is much more massive than the other bodies of the system combined, its speed relative to the center of mass of the most massive body.
An animation explaining why the planet Mercury may appear to move "backwards", or retrograde across Earth's sky. Apparent retrograde motion is the apparent motion of a planet in a direction opposite to that of other bodies within its system, as observed from a particular vantage point.
At a fixed point on the surface, the magnitude of Earth's gravity results from combined effect of gravitation and the centrifugal force from Earth's rotation. [ 2 ] [ 3 ] At different points on Earth's surface, the free fall acceleration ranges from 9.764 to 9.834 m/s 2 (32.03 to 32.26 ft/s 2 ), [ 4 ] depending on altitude , latitude , and ...