Editing Tidal acceleration (section)

=== Historical evidence ===
This mechanism has been working for 4.5 billion years, since oceans first formed on Earth, but less so at times when much or most of the water [[Snowball Earth|was ice]]. There is geological and paleontological evidence that Earth rotated faster and that the Moon was closer to Earth in the remote past. ''[[Rhythmites|Tidal rhythmites]]'' are alternating layers of sand and silt laid down offshore from [[estuary|estuaries]] having great tidal flows.  Daily, monthly and seasonal cycles can be found in the deposits. This geological record is consistent with these conditions 620 million years ago: the day was 21.9±0.4 hours, and there were 13.1±0.1 synodic months/year and 400±7 solar days/year.  The average recession rate of the Moon between then and now has been 2.17±0.31&nbsp;cm/year, which is about half the present rate. The present high rate may be due to near [[resonance]] between natural ocean frequencies and tidal frequencies.<ref>{{Cite journal|doi = 10.1029/1999RG900016|last1 = Williams|first1 = George E.|date = 2000|title = Geological constraints on the Precambrian history of Earth's rotation and the Moon's orbit|bibcode = 2000RvGeo..38...37W|journal = Reviews of Geophysics|volume = 38|issue = 1|pages = 37–60|citeseerx = 10.1.1.597.6421 | s2cid=51948507 }}</ref>

Analysis of layering in fossil [[mollusc shell]]s from 70 million years ago, in the [[Late Cretaceous]] period, shows that there were 372 days a year, and thus that the day was about 23.5 hours long then.<ref>{{Cite web|url=https://www.sciencedaily.com/releases/2020/03/200309135410.htm|title=Ancient shell shows days were half-hour shorter 70 million years ago: Beer stein-shaped distant relative of modern clams captured snapshots of hot days in the late Cretaceous|website=ScienceDaily|language=en|access-date=2020-03-14}}</ref><ref>{{Cite journal|last1=Winter|first1=Niels J. de|last2=Goderis|first2=Steven|last3=Malderen|first3=Stijn J. M. Van|last4=Sinnesael|first4=Matthias|last5=Vansteenberge|first5=Stef|last6=Snoeck|first6=Christophe|last7=Belza|first7=Joke|last8=Vanhaecke|first8=Frank|last9=Claeys|first9=Philippe|date=2020|title=Subdaily-Scale Chemical Variability in a Torreites Sanchezi Rudist Shell: Implications for Rudist Paleobiology and the Cretaceous Day-Night Cycle|journal=Paleoceanography and Paleoclimatology|language=en|volume=35|issue=2|pages=e2019PA003723|doi=10.1029/2019PA003723|issn=2572-4525|doi-access=free|bibcode=2020PaPa...35.3723W |hdl=1854/LU-8685501|hdl-access=free}}</ref>