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Mars comes closer to Earth more than any other planet save Venus at its nearest—56 million km is the closest distance between Mars and Earth, whereas the closest Venus comes to Earth is 40 million km. Mars comes closest to Earth every other year, around the time of its opposition, when Earth is sweeping between the Sun and Mars. Extra-close ...
If the same sphere were made of lead the small body would need to orbit just 6.7 mm above the surface for sustaining the same orbital period. When a very small body is in a circular orbit barely above the surface of a sphere of any radius and mean density ρ (in kg/m 3), the above equation simplifies to (since M = Vρ = 4 / 3 π a 3 ρ)
The equation of time vanishes only for a planet with zero axial tilt and zero orbital eccentricity. [5] Two examples of planets with large equations of time are Mars and Uranus. On Mars the difference between sundial time and clock time can be as much as 50 minutes, due to the considerably greater eccentricity of its orbit.
See Weight for detail of mass/weight distinction and conversion. Avoirdupois is a system of mass based on a pound of 16 ounces, while Troy weight is the system of mass where 12 troy ounces equals one troy pound. The symbol g 0 is used to denote standard gravity in order to avoid confusion with the (upright) g symbol for gram.
While the weight of an object varies in proportion to the strength of the gravitational field, its mass is constant, as long as no energy or matter is added to the object. [3] For example, although a satellite in orbit (essentially a free-fall) is "weightless", it still retains its mass and inertia.
In astrodynamics, an orbit equation defines the path of orbiting body around central body relative to , without specifying position as a function of time.Under standard assumptions, a body moving under the influence of a force, directed to a central body, with a magnitude inversely proportional to the square of the distance (such as gravity), has an orbit that is a conic section (i.e. circular ...
Simply, if Mars is assumed to be a static perfectly spherical body of radius R M, provided that there is only one satellite revolving around Mars in a circular orbit and such gravitation interaction is the only force acting in the system, the equation would be =,
The choice of solar mass, M ☉, as the basic unit for planetary mass comes directly from the calculations used to determine planetary mass.In the most precise case, that of the Earth itself, the mass is known in terms of solar masses to twelve significant figures: the same mass, in terms of kilograms or other Earth-based units, is only known to five significant figures, which is less than a ...