Tidal force Earth

Tidal forces have periods of 8.8 and 18.6 years [67]. The variations in the tidal forces arise because the orbital planes of the Moon and the Earth are slightly inclined with respect to each other and because the Sun, Moon, and Earth form a mutually rotating gravitational system so that the magnitude of the tidal force depends on their relative positions. 

Why temperatures and rainfall near Chesapeake Bay should be affected by variations of the tidal forces is not so clear. However the atmosphere and stratosphere are pulled away from the earth by tidal forces just as are the waters of the earth. These forces vary by as much as 10 percent during the tidal periods [67] resulting in density variations in the stratosphere with the same periods the consequent density variations may affect the relative rates of stratospheric chemical reactions, causing disturbances of temperature and rainfall on the ground with the tidal periodicities. 

Comets are generally considered to be weakly consolidated, and active comets are commonly observed to split into fragments. This is sometimes due to the tidal forces of a close planetary encounter, such as affected comet Shoemaker-Levy when it passed close to Jupiter in 1992 and broke into 21 pieces. More commonly, a comet spontaneously fragments multiple times over its orbit period, without any obvious cause. Disintegrating comets leave trails of small particles in their wakes. These trails are known as meteor streams, and when the Earth passes through such a meteor stream, as it does several times a year, a meteor shower occurs. Meter-sized rocks are known to occur within cometary meteor streams. 

Tidal forces exerted by the attraction of the moon and the sun (and to a minor extent by the planets) on the earth s body produce a wide spectrum of geodynamic phenomena, from primary luni-solar attractional effects to secondary induced effects like solid earth and ocean tides, and third order ocean loading effects. Since these phenomena affect precise geodetic observations and make them time-dependent it is necessary to reduce time-variable geodetic observables and derived quantities in order to correspond to a quasinstationary, time—invariant state. 

Essentially, this force is responsible for the revolutional motion of the moon around the earth (for refinements of these considerations see e. g. Bartels, 1957 or Ilk, 1983). Up to terms which are insignificant in the present context the tidal force acting at a mass particle of unit mass at P is simply the difference between (1) and (2)... 

It was a big surprise when on lo active volcanism was detected on its surface (see Eig. 4.1). On Earth, the heat source that produces volcanic activity comes from its interior where radioactive materials decay and release energy and also from heat left over from its formation, accretion heat. This however cannot explain the volcanism on lo. The satellite is too small and should have cooled out. The only mechanism to maintain active volcanism on lo is tidal heating (see also Moore, 2003 [236]). The semi major axis of the orbit of lo is 421800 km so it is close to Jupiter and exposed to strong tidal forces. One revolution around Jupiter takes only 1 d 18 h 27 min. The albedo of lo is 0.61 which is a relatively high value. Other parameters... 

On the surface of lo 400 active volcanoes and more than 150 mountains have been detected. There are volcanic plumes that extend up to 500 km. The tidal forces of Jupiter on lo are 6000 times stronger than those of the Moon on Earth. In addition to these forces, there are also tidal forces caused by the two other Galilean satellites Europa and Ganymede (these are comparable to the tidal force of the Moon). Furthermore, the strength of these forces varies because the orbit of lo is elliptical. The variation of the tidal forces of Jupiter due to lo s elliptical orbit is 1000 times the strength of the tidal forces of the Moon. 

On Earth, the tidal force cause deformations of the whole Earth s crust between 20 and 30 cm. On lo, the deformations can reach up to 300 m. 

Book II investigates the dynamical conditions of fluid motion. Book III displays the law of gi avitatioii at work in the solar system. It is demonstrated from the revolutions of the six known planets, including Earth, and their satellites, though Newton could never quite perfect the difficult theory of the Moon s motion. It is also demonstrated from the motions of comets. The gravitational forces of the heavenly bodies are used to calculate their relative masses. The tidal ebb and flow and the precession of the equinoxes is explained m terms of the forces exerted by the Sun and Moon. These demonstrations are carried out with precise calculations. 

Water masses on the earth always have a tendency to align their surfaces perpendicular to the direction of gravity. However, because of the enormous mass of the oceans, gravity disturbances cause oscillations forcing the water particles to move on trajectories that are nearly horizontal to their normal position. These horizontal movements, the tidal currents, have the same periodicities as the rising and falhng of the water level, which is caused by the attraction and withdrawal of water masses. 

Tsunamis are often caused by m or earthquakes at fault points deep beneath the ocean surface. The earth movements unleashes swells that race toward coasts. The task of oceanographers in such cases is to measure the speed and forces in the tidal waves in an attempt to limit the damage when they reach the shore. 

Tides and tidal currents are caused by the gravitational forces of the moon and the sun, the centrifugal force from the rotation of the earth and interaction or... 

The early dikes were just mounds of tamped earth. Along the coast the dikes require a seaward face that can withstand wave forces and tidal currents. Several different types of sea dikes were developed for this purpose. In the 13th century the mud dike was constructed with pieces of sod covered by a layer of seaweed on the dike s steep seaward side (Lambert, 1971). Many of these dikes were still in use in the 17th century. 

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