Editing Leaning Tower of Pisa (section)

== History following construction ==
Between 1589 and 1592,<ref>Some contemporary sources speculate about the exact date; e.g. Rachel Hilliam gives 1591 (''Galileo Galilei: Father of Modern Science'', The Rosen Publishing Group, 2005, p. 101).</ref> [[Galileo Galilei]], who lived in Pisa at the time, is said to have [[Galileo's Leaning Tower of Pisa experiment|dropped two cannonballs]] of different [[mass]]es from the tower to demonstrate that their speed of descent was independent of their mass, in keeping with the [[scientific law]] of [[free fall]]. The primary source for this is the biography ''Racconto istorico della vita di Galileo Galilei (Historical Account of the Life of Galileo Galilei)'', written by Galileo's pupil and secretary [[Vincenzo Viviani]] in 1654, but only published in 1717, long after his death.<ref>{{cite news |url=http://www.hindu.com/seta/2005/06/30/stories/2005063000351500.htm |archive-url=https://web.archive.org/web/20051102091621/http://www.hindu.com/seta/2005/06/30/stories/2005063000351500.htm |url-status=dead |archive-date=2 November 2005 |title=Sci Tech: Science history: setting the record straight |date=30 June 2005 |newspaper=[[The Hindu]] |access-date=5 May 2009}}</ref><ref>[http://brunelleschi.imss.fi.it/itineraries/biography/VincenzoViviani.html Vincenzo Viviani] {{Webarchive|url=https://web.archive.org/web/20160206182251/http://brunelleschi.imss.fi.it/itineraries/biography/VincenzoViviani.html |date=6 February 2016 }} on museo galileo</ref>

During [[World War II]], the [[Allies of World War II|Allies]] suspected that the Germans were using the tower as an observation post. Leon Weckstein, a [[U.S. Army]] [[sergeant]] sent to confirm the presence of German troops in the tower, was impressed by the beauty of the cathedral and its campanile, and thus refrained from ordering an [[artillery]] strike, sparing it from destruction.<ref name="tilt">{{cite book|last=Shrady|first=Nicholas |date=October 7, 2003|title=Tilt: a skewed history of the Tower of Pisa |publisher=[[Simon & Schuster]]|isbn=978-0-74-322926-5 |oclc=52086370|via=[[Archive.org]]|url-access=registration|pages=147–152 |url=https://archive.org/details/tiltskewedhistor0000shra/mode/2up|access-date=28 September 2023 }}</ref><ref>{{cite news |url=https://www.theguardian.com/theguardian/2000/jan/13/features11.g23 |title=Why I spared the Leaning Tower of Pisa |newspaper=The Guardian |date=12 January 2000 |access-date=19 July 2012 |archive-date=9 May 2014 |archive-url=https://web.archive.org/web/20140509082459/http://www.theguardian.com/theguardian/2000/jan/13/features11.g23 |url-status=live }}</ref>

Numerous efforts have been made to restore the tower to a vertical orientation or at least keep it from falling over. Most of these efforts failed; some worsened the tilt. On 27 February 1964, the government of Italy requested aid in preventing the tower from toppling. It was, however, considered important to retain the current tilt, due to the role that this element played in promoting the tourism industry of Pisa.<ref>{{cite news |url=https://query.nytimes.com/gst/fullpage.html?res=9B0DE5DE153EF932A35752C1A961948260 |work=The New York Times |title=Securing the Lean In Tower of Pisa |date=1 November 1987 |access-date=17 February 2017 |archive-date=14 February 2009 |archive-url=https://web.archive.org/web/20090214004751/http://query.nytimes.com/gst/fullpage.html?res=9B0DE5DE153EF932A35752C1A961948260 |url-status=live }}</ref>

Starting in 1993, 870 tonnes of lead [[counterweights]] were added, which straightened the tower slightly.<ref name= time2001>{{cite news |url=http://content.time.com/time/magazine/article/0,9171,1000167,00.html |magazine=[[Time (magazine)|TIME Magazine]] |title=Tipping the Balance |date=25 June 2001 |access-date=30 May 2020 |archive-date=23 November 2020 |archive-url=https://web.archive.org/web/20201123212536/http://content.time.com/time/magazine/article/0,9171,1000167,00.html |url-status=live }}</ref>

The tower and the neighbouring [[cathedral]], [[baptistery]], and cemetery are included in the [[Piazza del Duomo, Pisa|Piazza del Duomo]] [[World Heritage Site|UNESCO World Heritage Site]], which was declared in 1987.<ref>{{cite web |title=Piazza del Duomo, Pisa |url=https://whc.unesco.org/en/list/395 |publisher=[[UNESCO]] World Heritage Centre |access-date=8 August 2016 |archive-date=2 September 2016 |archive-url=https://web.archive.org/web/20160902082028/http://whc.unesco.org/en/list/395 |url-status=live }}</ref>

The tower was closed to the public on 7 January 1990,<ref name=closed1990>{{cite news |url=http://news.bbc.co.uk/onthisday/hi/dates/stories/january/7/newsid_4037000/4037997.stm |title=BBC on this day: 1990: Leaning Tower of Pisa closed to public |work=BBC News |access-date=29 April 2020 |archive-date=20 February 2020 |archive-url=https://web.archive.org/web/20200220055707/http://news.bbc.co.uk/onthisday/hi/dates/stories/january/7/newsid_4037000/4037997.stm |url-status=live }}</ref> after more than two decades of stabilisation studies and spurred by the abrupt collapse of the [[Civic Tower (Pavia)|Civic Tower of Pavia]] in 1989.<ref name="nytimes1989">{{cite news |last=Hofman |first=Paul |date=30 July 1989 |title=Italy's Endangered Treasures |url=https://www.nytimes.com/1989/07/30/travel/italy-s-endangered-treasures.html |work=[[New York Times]] |location=New York |access-date=29 April 2020 |archive-date=9 November 2020 |archive-url=https://web.archive.org/web/20201109042526/https://www.nytimes.com/1989/07/30/travel/italy-s-endangered-treasures.html |url-status=live }}</ref><ref name="latimes1989">{{cite news |last=Montalbo |first=William D |date=18 March 1989 |title=900-Year-Old Bell Tower Collapses in Italy; Three Killed |url=https://www.latimes.com/archives/la-xpm-1989-03-18-mn-119-story.html |work=[[Los Angeles Times]] |location=Los Angeles |access-date=29 April 2020 |archive-date=30 November 2020 |archive-url=https://web.archive.org/web/20201130083223/https://www.latimes.com/archives/la-xpm-1989-03-18-mn-119-story.html |url-status=live }}</ref> The bells were removed to relieve some weight, and cables were cinched around the third level and anchored several hundred meters away, and residences in the path of a potential collapse were vacated. The selected method for preventing the collapse of the tower was to slightly reduce its tilt to a safer angle by removing {{convert|38|m3|0|abbr=off}} of soil from underneath the raised end. The tower's tilt was reduced by {{convert|45|cm|in|frac=2|abbr=off}}, returning to its 1838 position. After a decade of corrective reconstruction and stabilization efforts, the tower was reopened to the public on 15 December 2001, and was declared stable for at least another 300 years.<ref name= time2001/> In total, {{convert|70|metric ton|short ton}} of soil were removed.<ref name=stabilized>{{cite news |last=Duff |first=Mark |url=http://news.bbc.co.uk/2/hi/europe/7423957.stm |title=Europe &#124; Pisa's leaning tower 'stabilised' |work=BBC News |date=28 May 2008 |access-date=5 May 2009 |archive-date=20 April 2013 |archive-url=https://web.archive.org/web/20130420121215/http://news.bbc.co.uk/2/hi/europe/7423957.stm |url-status=live }}</ref>

After a phase (1990–2001) of structural strengthening,<ref>[http://www.ingenia.org.uk/ingenia/articles.aspx?Index=322 A profile of an engineer employed to straighten the tower] {{Webarchive|url=https://web.archive.org/web/20120127115940/http://www.ingenia.org.uk/ingenia/articles.aspx?Index=322 |date=27 January 2012 }} ''Ingenia'', March 2005</ref> the tower has been undergoing gradual surface restoration to repair visible damage, mostly corrosion and blackening. These are particularly pronounced due to the tower's age and its exposure to wind and rain.<ref>{{Cite web |url=http://piazza.opapisa.it/index_pdm.html |title=Restoration work is mentioned at the official website of the square |access-date=14 May 2007 |archive-url=https://web.archive.org/web/20091025182652/http://piazza.opapisa.it/index_pdm.html |archive-date=25 October 2009 |url-status=dead }}</ref> In May 2008, engineers announced that the tower had been stabilized such that it had stopped moving for the first time in its history. They stated that it would be stable for at least 200 years.<ref name=stabilized />

A ceremony for the 850th anniversary of the laying of the foundation stone was held on 9 August 2023.<ref>{{cite news |title=La Torre Pendente di Pisa compie 850 anni |url=https://www.tgcom24.mediaset.it/cronaca/torre-di-pisa-compie-850-anni_68169958-202302k.shtml |access-date=8 August 2023 |agency=tgcom24.mediaset.it |publisher=tgcom24.mediaset.it |date=8 August 2023}}</ref>

<gallery mode="packed"| heights="315px">
File:Leaning_Tower_of_Pisa_in_the_1890s.jpg|Leaning Tower of Pisa in the 1890s<ref>{{Cite web |url=https://coololdphotos.com/leaning-tower-of-pisa-in-the-1890s/ |title=Leaning Tower of Pisa in the 1890s |last=Tom |date=2015-05-06 |website=Cool Old Photos |language=en-US |access-date=2019-03-05 |archive-date=6 March 2019 |archive-url=https://web.archive.org/web/20190306043931/https://coololdphotos.com/leaning-tower-of-pisa-in-the-1890s/ |url-status=live }}</ref>
File:Plaque galileo.jpg|Plaque in memory of [[Galileo Galilei]]'s experiments
File:Pisa schiefer turm gewichte 1998 01.jpg|Temporary lead counterweights, 1998
File:Pisa Cathedral & Leaning Tower of Pisa.jpg|The [[Pisa Baptistery|Baptistery]] (in the foreground), the [[Pisa Cathedral|Cathedral]] (in the middleground), and the Leaning Tower of Pisa (in the background)
</gallery>