Editing Tidal acceleration (section)

=== Angular momentum and energy ===
The gravitational torque between the Moon and the tidal bulge of Earth causes the Moon to be constantly promoted to a slightly higher orbit and Earth to be decelerated in its rotation.  As in any physical process within an isolated system, total [[energy]] and [[angular momentum]] are conserved.  Effectively, energy and angular momentum are transferred from the rotation of Earth to the orbital motion of the Moon (however, most of the energy lost by Earth (−3.78 TW)<ref name=":0">{{Cite journal|last1=Williams|first1=James G.|last2=Boggs|first2=Dale H.|date=2016|title=Secular tidal changes in lunar orbit and Earth rotation|url=http://link.springer.com/10.1007/s10569-016-9702-3|journal=Celestial Mechanics and Dynamical Astronomy|language=en|volume=126|issue=1|pages=89–129|doi=10.1007/s10569-016-9702-3|bibcode=2016CeMDA.126...89W |s2cid=124256137|issn=0923-2958|url-access=subscription}}</ref> is converted to heat by frictional losses in the oceans and their interaction with the solid Earth, and only about 1/30th (+0.121 TW) is transferred to the Moon). The Moon moves farther away from Earth (+38.30±0.08&nbsp;mm/yr), so its [[potential energy|potential energy, which is still negative]] (in Earth's [[gravity well]]), increases, i. e. becomes less negative. It stays in orbit, and from [[Laws of Kepler|Kepler's 3rd law]] it follows that its average [[angular velocity]] actually decreases, so the tidal action on the Moon actually causes an angular deceleration, i.e. a negative acceleration (−25.97±0.05"/century<sup>2</sup>) of its rotation around Earth.<ref name=":0" /> The actual speed of the Moon also decreases. Although its [[kinetic energy]] decreases, its potential energy increases by a larger amount, i. e.  E<sub>p</sub> = -2E<sub>c</sub> ([[Virial theorem|Virial Theorem]]).

The rotational angular momentum of Earth decreases and consequently the length of the day increases. The ''net'' tide raised on Earth by the Moon is dragged ahead of the Moon by Earth's much faster rotation. '''Tidal friction''' is required to drag and maintain the bulge ahead of the Moon, and it dissipates the excess energy of the exchange of rotational and orbital energy between Earth and the Moon as heat. If the friction and heat dissipation were not present, the Moon's gravitational force on the tidal bulge would rapidly (within two days) bring the tide back into synchronization with the Moon, and the Moon would no longer recede. Most of the dissipation occurs in a turbulent bottom boundary layer in shallow seas such as the [[European Shelf]] around the [[British Isles]], the [[Patagonian Shelf]] off [[Argentina]], and the [[Bering Sea]].<ref>{{Cite journal|doi = 10.1016/S0079-6611(97)00021-9|last1 = Munk|first1 = Walter|date = 1997|title = Once again: once again—tidal friction|journal = Progress in Oceanography|volume = 40|issue = 1–4|pages = 7–35|bibcode = 1997PrOce..40....7M }}</ref>

The dissipation of energy by tidal friction averages about 3.64 terawatts of the 3.78 terawatts extracted, of which 2.5 terawatts are from the principal M{{sub|2}} lunar component and the remainder from other components, both lunar and solar.<ref name=":0" /><ref name=Munk1998>{{Cite journal|author = Munk, W.|date = 1998|title = Abyssal recipes II: energetics of tidal and wind mixing|journal = Deep-Sea Research Part I|volume = 45|issue = 12|pages = 1977–2010|doi = 10.1016/S0967-0637(98)00070-3|last2 = Wunsch|first2 = C|bibcode = 1998DSRI...45.1977M }}</ref>

An ''[[equilibrium tide|equilibrium tidal]] bulge'' does not really exist on Earth because the continents do not allow this mathematical solution to take place. Oceanic tides actually rotate around the ocean basins as vast ''[[gyre]]s'' around several ''[[amphidromic point]]s'' where no tide exists. The Moon pulls on each individual undulation as Earth rotates—some undulations are ahead of the Moon, others are behind it, whereas still others are on either side. The "bulges" that actually do exist for the Moon to pull on (and which pull on the Moon) are the net result of integrating the actual undulations over all the world's oceans.