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The planetary hours are an ancient system in which one of the seven classical planets is given rulership over each day and various parts of the day. Developed in Hellenistic astrology, it has possible roots in older Babylonian astrology, and it is the origin of the names of the days of the week as used in English and numerous other languages.
In astronomy, Kepler's laws of planetary motion, published by Johannes Kepler in 1609 (except the third law, and was fully published in 1619), describe the orbits of planets around the Sun. These laws replaced circular orbits and epicycles in the heliocentric theory of Nicolaus Copernicus with elliptical orbits and explained how planetary ...
Right-hand rule for cross product. The cross product of vectors and is a vector perpendicular to the plane spanned by and with the direction given by the right-hand rule: If you put the index of your right hand on and the middle finger on , then the thumb points in the direction of . [4] Fleming's right hand rule
The various FBI mnemonics (for electric motors) show the direction of the force on a conductor carrying a current in a magnetic field as predicted by Fleming's left hand rule for motors [1] and Faraday's law of induction. Other mnemonics exist that use a right hand rule for predicting resulting motion from a preexisting current and field.
Brahe took extraordinarily accurate measurements of the motion of the planets of the Solar System. From these measurements, Kepler was able to formulate Kepler's laws, the first modern description of planetary motion: The orbit of every planet is an ellipse with the Sun at one of the two foci.
"a slight new phrasing of this law permits us to include not only planetary orbits around the Sun, but also the orbits of moons around their parent planets." [24] The new phrasing is known as “Dermott's law”. Of the recent discoveries of extrasolar planetary systems, few have enough known planets to test whether similar rules apply.
Catching a glimpse of the planets will depend on the time of day and their relative distance from the planet at the time. For example, Venus, Saturn and Jupiter are best viewed after sunset at ...
Planetary gravity dominates the behavior of the spacecraft in the vicinity of a planet and in most cases Hohmann severely overestimates delta-v, and produces highly inaccurate prescriptions for burn timings. A relatively simple way to get a first-order approximation of delta-v is based on the 'Patched Conic Approximation' technique. One must ...