FACTOID # 22: South Dakota has the highest employment ratio in America, but the lowest median earnings of full-time male employees.
 
 Home   Encyclopedia   Statistics   States A-Z   Flags   Maps   FAQ   About 
   
 
WHAT'S NEW
 

SEARCH ALL

FACTS & STATISTICS    Advanced view

Search encyclopedia, statistics and forums:

 

 

(* = Graphable)

 

 


Encyclopedia > Tidal locking

Tidal locking makes one side of an astronomical body always face another, like the Moon facing the Earth. A tidally locked body takes just as long to rotate around its own axis as it does to revolve around its partner. This causes only one constant side or hemisphere to face the partner body. The most common situation in our solar system is for a satellite to face its planet (like our Moon). However, if the difference in mass between the two bodies and their separation is small, both may become tidally locked to each other. The best-known example of this is between Pluto and Charon. Bulk composition of the moons mantle and crust estimated, weight percent Oxygen 42. ... Earth (often referred to as The Earth) is the third planet in the solar system in terms of distance from the Sun, and the fifth in order of size. ... A satellite is any object that orbits another object (which is known as its primary). ... A planet is generally considered to be a relatively large mass of accreted matter in orbit around a star. ... Adjective Plutonian Atmospheric characteristics Atmospheric pressure 0. ... Charon may refer to: Charon (mythology) - the figure from Greek, and later Christian mythology, who ferried the dead across the river Acheron in the underworld Hades and Hell, respectively. ...

Contents


Earth's Moon

In the case of the Moon, both its rotation and orbital period are just over 4 weeks. The effect is that no matter where you are on the Earth you always see the same face of the Moon. The entirety of the far side of the Moon was not seen until 1959, when photographs were transmitted from the Soviet spacecraft Luna 3. Far side of the Moon. ... 1959 (MCMLIX) was a common year starting on Thursday of the Gregorian calendar. ... Soviet redirects here. ... Luna 3, an automatic interplanetary station of the Luna program, was the third spacecraft successfully launched to the Moon and the first to return images of the lunar far side. ...


(More precisely, despite the Moon's rotational and orbital periods being exactly locked, we may actually see about 59% of the moon's total surface with repeated observations due to the phenomenon of librations. These are primarily caused by the Moon's varying orbital speed due to the eccentricity of its orbit.) Although the Moon keeps the same side towards Earth, careful observations will reveal you can actually see 59% of the Moons surface. ... Look up Eccentricity in Wiktionary, the free dictionary. ...


Mechanism

Gravitational attraction between two bodies produces a tidal force on each of them, stretching each body along the axis oriented towards its partner and compressing it along the other two perpendicular axes. This will distort the orbiting bodies' shapes slightly. Larger astronomical bodies which are near-spherical due to self-gravitation, become slightly prolate (ovoid) (note that if the body is sufficiently small, gravity may not overcome its structural integrity; larger bodies are essentially fluid at the large scale). Comet Shoemaker-Levy 9 after breaking up under the influence of Jupiters tidal forces. ... Perpendicular is a geometric term that may be used as a noun or adjective. ... In mathematics, a spheroid is a quadric surface in three dimensions obtained by rotating an ellipse about one of its principal axes. ...


If either of the two orbiting bodies is rotating relative to the other, this prolate shape is not stable. The rotation of the body will cause its long axis to move out of alignment with the other object, and the tidal force will have to reshape it to restore the situation. In a sense, the tidal bulges "move" around the body as it rotates to stay in alignment with the other object. This is most clearly seen on Earth by how the ocean tides rise and fall with the rising and setting of the Moon. [[Image:http://www. ... The tide is the cyclic rising and falling of Earths ocean surface caused by the tidal forces of the Moon and the Sun acting on the Earth. ... Bulk composition of the moons mantle and crust estimated, weight percent Oxygen 42. ...


Since it takes a small but nonzero amount of time for the bulge to shift position, it is always located slightly away from the nearest point to the other object. For the case of a rotation period shorter than the orbital period, this bulge is located in the direction of the rotation. This misalignment causes a small but steady and significant force acting to slow the rotation of the body. This is because the bulge is pulled on by the other object's gravity, resulting in a slight force pulling the surface of the body in the opposite direction of its rotation. The rotation of the body slowly decreases, with its orbital momentum being boosted in the process. In the opposite case of a rotation period longer than the orbital period, the rate of rotation is increased at the expense of orbital momentum instead.


The tidal locking effect is also experienced by the "planet", but at a vastly slower rate. For example, the Earth's rotation is gradually slowing down because of the Moon, by an amount that becomes noticeable over geological time in some fossils. For similar sized bodies the effect may be of comparable size for both, and both may become tidally locked to each other. Pluto and Charon are good examples of this - you can only see Charon from one hemisphere of Pluto! Adjective Plutonian Atmospheric characteristics Atmospheric pressure 0. ... Charon may refer to: Charon (mythology) - the figure from Greek, and later Christian mythology, who ferried the dead across the river Acheron in the underworld Hades and Hell, respectively. ...


Tidal locking is a purely gravitational effect, and does not require the bodies to be planets and moons. For example, it is thought that many binary stars are mutually tidally locked. A binary star system consists of two stars both orbiting around their barycenter. ...


The effect carries over largely unchanged for small and non-spheroidal bodies. The main difference is that the tidal bulges travel over the irregular surface of the objects, rather than over a sphere.


Finally, in some cases where the orbit is eccentric and the tidal effect is relatively weak, the smaller body may end up in an orbital resonance, rather than tidally locked. Here the ratio of rotation period to orbital period is some well-defined fraction different from 1:1. A well known case is the rotation of Mercury - locked to its orbit around the Sun in a 3:2 resonance. Eccentric is from the Greek for out of the centre, as opposed to concentric, in the centre. ... In celestial mechanics, orbital resonance occurs when two orbiting bodies have periods of revolution that are in a simple integer ratio so that they exert a regular gravitational influence on each other. ... Note: This article contains special characters. ...


Occurrence

Moons

Most significant moons in the Solar System are tidally locked with their primaries, since they orbit very closely and tidal force increases rapidly (as a cubic) with decreasing distance. Notable exceptions are the irregular satellites of the gas giant planets, which orbit much further away than the large well-known moons. The solar system comprises the Earths Sun and the retinue of celestial objects gravitationally bound to it. ... Polynomial of degree 3 In mathematics, a cubic function is a function of the form where a is nonzero; or in other words, a polynomial of degree three. ... A gas giant is a large planet that is not composed mostly of rock or other solid matter. ...


Pluto and its moon Charon are an extreme example of a tidal lock. Charon is the biggest moon in the Solar System in comparison to its planet and also has a very close orbit. This has made Pluto also tidally locked to Charon. In effect, these two celestial bodies revolve around each other (their mass center lies outside of Pluto) as if joined with a rod connecting two opposite points on their surfaces. Adjective Plutonian Atmospheric characteristics Atmospheric pressure 0. ... Media:Example. ... In physics, an orbit is the path that an object makes, around another object, whilst under the influence of a source of centripetal force, such as gravity. ... See lists of astronomical objects for a list of the various lists of astronomical objects in Wikipedia. ... It has been suggested that this article or section be merged with Center of gravity. ...


The tidal locking situation for asteroid moons is largely unknown, but closely-orbiting binaries are expected to be tidally locked, as well as, obviously, contact binaries. 243 Ida and its moon Dactyl An asteroid moon is an asteroid that orbits another asteroid. ... In astronomy, the term contact binary refers to two astronomical bodies that are so close that they touch each other. ...


Planets

Until radar observations in 1965 proved otherwise, it was thought that Mercury was tidally locked with the Sun. Instead, it turned out that Mercury has a 3:2 spin-orbit resonance, rotating three times for every two revolutions around the Sun; the eccentricity of Mercury's orbit makes this resonance stable. The original reason astronomers thought it was tidally locked was because whenever Mercury was best placed for observation, it was always at the same point in its 3:2 resonance, so showing the same face, which would be also the case if it were totally locked. 1965 (MCMLXV) was a common year starting on Friday (the link is to a full 1965 calendar). ... Note: This article contains special characters. ...


More subtly, the planet Venus may be tidally locked with the planet Earth: whenever the two are at their closest approach to each other in their orbits, Venus always has the same face towards Earth[citation needed]. (The tidal forces involved in this lock are extremely small and it may be primarily a result of coincidence; see the article on Venus for more detail.) In general, any object that orbits another massive object closely for long enough periods is likely to be tidally locked to it. (*min temperature refers to cloud tops only) Atmospheric characteristics Atmospheric pressure 9. ... Earth (often referred to as The Earth) is the third planet in the solar system in terms of distance from the Sun, and the fifth in order of size. ... (*min temperature refers to cloud tops only) Atmospheric characteristics Atmospheric pressure 9. ...


Stars

Close binary stars throughout the universe are expected to be tidally locked with each other, and extrasolar planets that have been found to orbit their primaries extremely closely are also thought to be tidally locked to them. One example, confirmed by MOST, is Tau Bo├Âtis, but strangely in this case it is a star tidally locked by a planet. Artists impression of a binary star system consisting of a black hole, with an accretion disc around it, and a main sequence star. ... Infrared image of the star GQ Lupi (A) orbited by a planet (b) at a distance of approximately 20 times the distance between Jupiter and our Sun. ... The Microvariability and Oscillations of STars telescope or the MOST space observatory is Canadas first and (as of mid-2005) only space telescope. ... Tau Boötis (Ï„ Boo / Ï„ Boötis) is a 4th magnitude star in the constellation of Boötes. ...


See Also


  Results from FactBites:
 
Tidal locking - Wikipedia, the free encyclopedia (1188 words)
Tidal locking is a purely gravitational effect, and does not require the bodies to be planets and moons.
The tidal locking situation for asteroid moons is largely unknown, but closely-orbiting binaries are expected to be tidally locked, as well as, obviously, contact binaries.
Close binary stars throughout the universe are expected to be tidally locked with each other, and extrasolar planets that have been found to orbit their primaries extremely closely are also thought to be tidally locked to them.
Tidal force - Wikipedia, the free encyclopedia (871 words)
The tidal force is a secondary effect of the force of gravity and is responsible for the tides.
Tidal effects become particularly pronounced near small bodies of high mass, such as neutron stars or fl holes, where they are responsible for the "spaghettification" of infalling matter.
Tidal forces, in combination with centripetal forces, create the oceanic tide of Earth's oceans, where the attracting bodies are the Moon and the Sun.
  More results at FactBites »

 
 

COMMENTARY     


Share your thoughts, questions and commentary here
Your name
Your comments

Want to know more?
Search encyclopedia, statistics and forums:

 


Press Releases |  Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms, 1022, m