Editing Eiffel Tower (section)

===Wind and weather considerations===
[[File:Lightning striking the Eiffel Tower - NOAA.jpg|thumb|upright=0.8|left|Lightning striking the Eiffel Tower in 1902]]
When it was built, Eiffel was accused of trying to create something artistic with no regard to the principles of engineering. However, Eiffel and his team were experienced bridge builders. In an interview with the newspaper ''[[Le Temps (Paris)|Le Temps]]'' published on 14 February 1887, Eiffel said:

{{blockquote|style=text-align:justify|Is it not true that the very conditions which give strength also conform to the hidden rules of harmony?{{nbsp}}... Now to what phenomenon did I have to give primary concern in designing the Tower? It was wind resistance. Well then! I hold that the curvature of the monument's four outer edges, which is as mathematical calculation dictated it should be{{nbsp}}... will give a great impression of strength and beauty, for it will reveal to the eyes of the observer the boldness of the design as a whole.<ref name=debate>{{cite web|url=http://www.toureiffel.paris/en/everything-about-the-tower/themed-files/71.html |title=Debate and controversy surrounding the Eiffel Tower |author=SETE |website=Official Eiffel Tower website |access-date=2 January 2013 |url-status=dead |archive-url=https://web.archive.org/web/20150908052239/http://www.toureiffel.paris/en/everything-about-the-tower/themed-files/71.html |archive-date=8 September 2015 |df=dmy }}</ref>}}

He used graphical methods to determine the strength of the tower and [[empirical evidence]] to account for the effects of wind, rather than a mathematical formula. Close examination of the tower reveals a basically [[Exponential function|exponential]] shape.<ref name="sciencedaily2005">{{cite web|url=https://www.sciencedaily.com/releases/2005/01/050106111209.htm |title=Elegant shape of Eiffel Tower solved mathematically by University of Colorado professor |website=Science Daily |date=7 January 2005 |access-date=24 May 2010}}</ref> All parts of the tower were overdesigned to ensure maximum resistance to wind forces. The top half was assumed to have no gaps in the latticework.<ref>Watson, 1992 p. 807.</ref> After it was completed, some have put forward various mathematical hypotheses in an attempt to explain the success of the design. A one devised in 2004 after letters sent by Eiffel to the French Society of Civil Engineers in 1885 were translated into English described it as a non-linear integral equation based on counteracting the wind pressure on any point of the tower with the tension between the construction elements at that point.<ref name="sciencedaily2005"/>

The Eiffel Tower sways by up to {{convert|9|cm|in|abbr=on}} in the wind.<ref>{{cite web|url=http://www.toureiffel.paris/en/faq/115.html |title=FAQ: History/Technical |author=SETE |website=Official Eiffel Tower website |access-date=16 April 2016 |url-status=dead |archive-url=https://web.archive.org/web/20160408210156/http://www.toureiffel.paris/en/faq/115.html |archive-date=8 April 2016 }}</ref>

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