What is Length of day?
The '''length of the day''' is how long a [[wikt:day|day]] is. On [[Earth]], a [[sidereal day]] is 23 hours and 56 minutes long, and a [[solar day]] is 24 hours. There are other [[planet]]s with different types of day. == Length of the day on other planets == This uses Earth time.<ref>[http://www.enchantedlearning.com/subjects/astronomy/planets/ Enchanted Learning.com]</ref> * [[Mercury (planet)|Mercury]] - about 59 days * [[Venus (planet)|Venus]] - 243 days * [[Earth]] - 1 day * [[Mars (planet)|Mars]] - about 1 day, 0.6 hours * [[Jupiter (planet)|Jupiter]] - 9 hours * [[Saturn (planet)|Saturn]] - about 10 hours * [[Uranus (planet)|Uranus]] - about 13 hours * [[Neptune (planet)|Neptune]] - about 15 hours == Increasing day length on Earth == The Earth is constantly losing [[angular velocity]] and [[rotational energy]] through a process called [[tidal acceleration]], which leads to a slow lengthening of the day. Tidal acceleration is an effect of the tidal forces between an orbiting natural satellite (e.g. the [[Moon]]), and the primary planet that it orbits (e.g. Earth). A century ago, the average day was about 1.7 [[millisecond]]s shorter than today.<ref>McCarthy D.D. & Seidelmann P.K. 2009. ''Time: from Earth rotation to atomic physics''. Weinheim: Wiley-VCH, pp. 88&ndash;89</ref> In the late [[Neoproterozoic]] about 620 million years ago a day had only about 21.9±0.4 hours.<ref>{{Cite journal | doi = 10.1029/1999RG900016 | last1 = Williams | first1 = George E. | year = 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 | s2cid = 51948507 }}</ref> == Related pages == *[[Sidereal day]] *[[Rotation period]] == References == {{commonscat|Day length}} {{reflist}} [[Category:Days]] [[Category:Earth sciences]] {{Science-stub}}