Editing Perpetual motion (section)

=== Low friction ===
* In [[flywheel energy storage]], "modern flywheels can have a zero-load rundown time measurable in years".<ref>{{Ref patent |country=WO
 |number= 2008037004
 |status= application
 |title= An energy storage device and method of use
 |pubdate= 2008-04-03
 |fdate= 2007-09-25
 |pridate= 2006-09-25
 |invent1= Kwok, James
}}</ref>
* Once spun up, objects in the vacuum of space—stars, black holes, planets, moons, [[spin-stabilized satellite]]s, etc.—dissipate energy very slowly, allowing them to spin for long periods. [[Tide]]s on Earth are dissipating the gravitational energy of the Moon/Earth system at an [[average]] rate of about 3.75 [[terawatt]]s.<ref name=Munk1998>{{Cite journal
|last = Munk |first = W.
|year = 1998
|title = Abyssal recipes II: energetics of tidal and wind mixing
|journal = Deep-Sea Research Part I: Oceanographic Research Papers
|volume = 45
|issue = 12
|page = 1977
|doi = 10.1016/S0967-0637(98)00070-3
|last2 = Wunsch
|first2 = C
|bibcode = 1998DSRI...45.1977M }}</ref><ref name=Ray1996>{{Cite journal
|last = Ray | first = R. D.
|year = 1996
|title = Detection of tidal dissipation in the solid Earth by satellite tracking and altimetry
|journal = Nature
|volume = 381
|issue = 6583
|page = 595
|doi = 10.1038/381595a0
|last2 = Eanes
|first2 = R. J.
|last3 = Chao
|first3 = B. F.
|bibcode = 1996Natur.381..595R |s2cid = 4367240
}}</ref>