Editing Tidal force (section)

== Effects ==
[[File:Saturn PIA06077.jpg|thumb|left|Figure 4: [[Saturn]]'s rings are inside the orbits of its principal moons. Tidal forces oppose gravitational coalescence of the material in the rings to form moons.<ref name=MacKay>{{cite book |author=R. S. MacKay |author2=J. D. Meiss |title=Hamiltonian Dynamical Systems: A Reprint Selection |page=36 |url=https://books.google.com/books?id=uTeqNsyj86QC&q=tidal+force&pg=PA36 |isbn=978-0-85274-205-1 |date=1987 |publisher=[[CRC Press]]}}</ref>]]

In the case of an infinitesimally small elastic sphere, the effect of a tidal force is to distort the shape of the body without any change in volume. The sphere becomes an [[ellipsoid]] with two bulges, pointing towards and away from the other body. Larger objects distort into an [[ovoid]], and are slightly compressed, which is what happens to the Earth's oceans under the action of the Moon. All parts of the Earth are subject to the Moon's gravitational forces, causing the water in the oceans to redistribute, forming bulges on the sides near the Moon and far from the Moon.<ref name=Americana>
{{cite book
 | title=The Encyclopedia Americana: A Library of Universal Knowledge
 | author=Rollin A Harris
 | pages=611–617
 | url=https://books.google.com/books?id=r8BPAAAAMAAJ&q=tidal+force&pg=PA612
 | publisher=Encyclopedia Americana Corp.
 | date=1920
 | volume=26
}}</ref>

When a body rotates while subject to tidal forces, internal friction results in the gradual dissipation of its rotational kinetic energy as heat. In the case for the Earth, and Earth's Moon, the loss of rotational kinetic energy results in a gain of about 2 milliseconds per century. If the body is close enough to its primary, this can result in a rotation which is [[Tidal locking|tidally locked]] to the orbital motion, as in the case of the Earth's moon. [[Tidal heating]] produces dramatic volcanic effects on Jupiter's moon [[Io (moon)|Io]]. {{anchor|Stress}}[[Stress (mechanics)|Stresses]] caused by tidal forces also cause a regular monthly pattern of [[moonquake]]s on Earth's Moon.<ref name="Tyson">{{Cite web|url=http://www.haydenplanetarium.org/tyson/read/1995/11/01/the-tidal-force|title=The Tidal Force {{!}} Neil deGrasse Tyson|website=www.haydenplanetarium.org|access-date=2016-10-10}}</ref>

Tidal forces contribute to ocean currents, which moderate global temperatures by transporting heat energy toward the poles. It has been suggested that variations in tidal forces correlate with cool periods in the global temperature record at 6- to 10-year intervals,<ref>{{cite journal |last1=Keeling |first1=C. D. |last2=Whorf |first2=T. P. |title=Possible forcing of global temperature by the oceanic tides |journal=Proceedings of the National Academy of Sciences |date=5 August 1997 |volume=94 |issue=16 |pages=8321–8328 |doi=10.1073/pnas.94.16.8321 |pmid=11607740 |bibcode=1997PNAS...94.8321K |pmc=33744 |doi-access=free }}</ref> and that [[beat (acoustics)|harmonic beat]] variations in tidal forcing may contribute to millennial climate changes. No strong link to millennial climate changes has been found to date.<ref>{{cite journal |last1=Munk |first1=Walter |last2=Dzieciuch |first2=Matthew |last3=Jayne |first3=Steven |title=Millennial Climate Variability: Is There a Tidal Connection? |journal=Journal of Climate |date=February 2002 |volume=15 |issue=4 |pages=370–385 |doi=10.1175/1520-0442(2002)015<0370:MCVITA>2.0.CO;2 |bibcode=2002JCli...15..370M |doi-access=free }}</ref>
[[File:Shoemaker-levy-tidal-forces.jpg|thumb|upright=1.25|Figure 5: [[Comet Shoemaker-Levy 9]] in 1994 after breaking up under the influence of [[Jupiter]]'s tidal forces during a previous pass in 1992.]]

Tidal effects become particularly pronounced near small bodies of high mass, such as [[neutron star]]s or [[black hole]]s, where they are responsible for the "[[spaghettification]]" of infalling matter. Tidal forces create the oceanic [[tide]] of [[Earth]]'s oceans, where the attracting bodies are the [[Moon]] and, to a lesser extent, the [[Sun]]. Tidal forces are also responsible for [[tidal locking]], [[tidal acceleration]], and tidal heating. [[Tidal triggering of earthquakes|Tides may also induce seismicity]].

By generating conducting fluids within the interior of the Earth, tidal forces also affect the [[Earth's magnetic field]].<ref>{{cite journal | date=23 September 1989 | title=Hungry for Power in Space | url=https://books.google.com/books?id=FPEUAQAAMAAJ | journal=New Scientist | volume=123 | pages=52 | access-date=14 March 2016}}</ref>

[[File:Supermassive black hole rips star apart (simulation).webm|thumb|Figure 6: This simulation shows a [[star]] getting torn apart by the gravitational tides of a [[supermassive black hole]].]]