Editing Pendulum clock (section)

===Local gravity===
[[File:Reloj de pendulo Ansonia C-1904.jpg|thumb|upright|Pendulum clock Ansonia. C. 1904, SANTIAGO, hanging oak gingerbread clock, eight-day time and strike.]]
Since the pendulum rate will increase with an increase in gravity, and local [[gravitational acceleration]] <math>g</math> varies with latitude and elevation on Earth, the highest precision pendulum clocks must be readjusted to keep time after a move. For example, a pendulum clock moved from sea level to {{convert|4000|ft}} will lose 16 seconds per day.<ref>{{cite web
 |last        = Arnstein
 |first       = Walt
 |title       = The Gravity Pendulum and its Horological Quirks
 |work        = Community Articles
 |publisher   = Timezone.com website
 |url         = http://www.timezone.com/library/comarticles/comarticles0013
 |access-date  = 2011-04-01
 |url-status     = dead
 |archive-url  = https://archive.today/20130204110512/http://www.timezone.com/library/comarticles/comarticles0013
 |archive-date = 2013-02-04
}}</ref>   With the most accurate pendulum clocks, even moving the clock to the top of a tall building would cause it to lose measurable time due to lower gravity.<ref>{{cite journal
 | last = Gore
 | first = Jeff
 | author2=Alexander van Oudenaarden
 | title = The Yin and Yang of Nature
 | journal = Nature
 | volume = 457
 | issue = 7227
 | pages = 271–2
 | publisher = MacMillan
 | date = January 15, 2009
 | url = http://web.mit.edu/biophysics/papers/NATURENV2009.pdf
 | doi = 10.1038/457271a
 | access-date = 2009-07-22
 | pmid = 19148089|bibcode = 2009Natur.457..271G | s2cid = 205043569
 }}</ref> The local gravity also varies by about 0.5% with [[latitude]] between the [[equator]] and the poles, with gravity increasing at higher latitudes due to the [[oblate]] shape of the Earth. Thus precision regulator clocks used for [[celestial navigation]] in the early 20th century had to be recalibrated when moved to a different latitude.