Editing Tide (section)

=== Dissipation ===
{{See also|Tidal acceleration}}
<!--this seems misleading in terms of the oceanography. Is this global average? Cites please!: Because the lunar tidal forces drive the oceans with a period of about 12.42 hours, which is considerably less than the natural period of the oceans, complex resonance phenomena take place. This, as well as the effects of friction, gives rise to an average lag time of 11 minutes between the occurrence of high water and lunar zenith. This tidal lag time corresponds to an angle of about 3 degrees between the position of the Moon, the center of the Earth, and the location of the global average high water.

Regarding the Earth–Moon system by itself (excluding the sun for the moment) unless both bodies' spin axes align perpendicularly to the orbital plane, oscillations result. Such oscillations contribute to tidal dissipation.

Dissipation by internal fluctuating deformations of the Earth due to the lunar tidal force is small compared with the dissipation in the Earth's oceans and seas, which account for 98% of the reduction of the Earth's rotational energy.<ref name="Ray1996">{{Cite journal |last1=Ray |first1=R.D. |year=1996 |title=Detection of tidal dissipation in the solid Earth by satellite tracking and altimetry |journal=[[Nature (journal)|Nature]] |volume=381 |issue=6583 |pages=595 |doi=10.1038/381595a0 |last2=Eanes |first2=R.J. |last3=Chao |first3=B.F. |bibcode=1996Natur.381..595R}}</ref> This lack of alignment is the case for the Earth–Moon system. Thus, besides tidal bulges, opposite to each other and comparable in size, that are associated with the so-called equilibrium tide,<ref name=Boon>{{cite book |title=Secrets of the Tide: Tide and Tidal Current Analysis and Applications, Storm Surges and Sea Level Trends |last=Boon |first=John D. |url=https://books.google.com/books?id=l75xhGEZ550C&pg=PA13&dq=%22equilibrium+tide%22 |isbn=1-904275-17-6 |publisher=Hollywood Publishing |year=2004 |pages=Chapter 2 pp. 13–end |oclc=57495983 |no-pp=true |via=[[Google Books]]}}</ref> additionally, surface oscillations commonly known as the dynamical tide, characterized by a wide variety of harmonic frequencies, is established.<ref name=Toledano>{{cite journal |url=https://arxiv.org/abs/astro-ph/0610563v1 |first1=Oswaldo |last1=Toledano |first2=Edmundo |last2=Moreno |first3=Gloria |last3=Koenigsberger |first4=R. |last4=Detmers |first5=Norbert |last5=Langer |date=18 October 2006 |title=Tides in asynchronous binary systems |journal=[[Astrophysics (journal)|Astrophysics]]</ref><ref name=Lamb>{{cite book |title=Hydrodynamics |last=Lamb |first=Horace |url=https://archive.org/details/hydrodynamics02lambgoog |quote=dynamical tide. |year=1916 |publisher=[[Cambridge University Press]] |edition=4th |page=[https://archive.org/details/hydrodynamics02lambgoog/page/n359 339] |isbn=0-521-45868-4 |oclc=30070401 31079426 33629948}} </ref><ref name=Americana>{{cite book |title=The Encyclopedia Americana: A Library of Universal Knowledge |last=Harris |first=Rollin A. |publisher=Encyclopedia Americana |year=1918 |url=https://books.google.com/books?d=CF4fijqC9GgC&pg=RA1-PA613&dq=%22equilibrium+tide%22 |pages=Article on Tides, pp. 613–614 |no-pp=true |via=[[Google Books]]}}</ref>
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Earth's tidal oscillations introduce dissipation at an [[average]] rate of about 3.75 [[terawatt]]s.<ref name=Munk1998>{{Cite journal |last1=Munk |first1=W. |date=1998 |title=Abyssal recipes II: energetics of tidal and wind mixing |journal=Deep-Sea Research Part I |volume=45 |issue=12 |page=1977 |doi=10.1016/S0967-0637(98)00070-3 |last2=Wunsch |first2=C. |bibcode=1998DSRI...45.1977M}}</ref> About 98% of this dissipation is by marine tidal movement.<ref name="Ray1996">{{Cite journal |last1=Ray |first1=R.D. |year=1996 |title=Detection of tidal dissipation in the solid Earth by satellite tracking and altimetry |journal=[[Nature (journal)|Nature]] |volume=381 |issue=6583 |pages=595 |doi=10.1038/381595a0 |last2=Eanes |first2=R.J. |last3=Chao |first3=B.F. |bibcode=1996Natur.381..595R|s2cid=4367240 }}</ref> Dissipation arises as basin-scale tidal flows drive smaller-scale flows which experience turbulent dissipation. This tidal drag creates torque on the moon that gradually transfers angular momentum to its orbit, and a gradual increase in Earth–moon separation. The equal and opposite torque on the Earth correspondingly decreases its rotational velocity. Thus, over geologic time, the moon recedes from the Earth, at about {{convert|3.8|cm|in}}/year, lengthening the terrestrial day.{{efn|The day is currently lengthening at a rate of about 0.002 seconds per century.<ref>Lecture 2: The Role of Tidal Dissipation and the Laplace Tidal Equations by Myrl Hendershott. GFD Proceedings Volume, 2004, [[Woods Hole Oceanographic Institution|WHOI]] Notes by Yaron Toledo and Marshall Ward.</ref>}}

[[Tidal acceleration|Day length has increased]] by about 2 hours in the last 600 million years. Assuming (as a crude approximation) that the deceleration rate has been constant, this would imply that 70 million years ago, day length was on the order of 1% shorter with about 4 more days per year.