Editing Millennium Bridge, London (section)

==Opening==
The bridge opened on 10 June 2000, one month late.<ref>{{cite news|title=Queen dedicates Millennium Bridge|url=http://news.bbc.co.uk/2/hi/uk_news/741512.stm|publisher=[[BBC News]]|date=9 May 2000|access-date=1 February 2023}}</ref> Unexpected lateral vibration due to [[Resonance|resonant]] structural response caused the bridge to be closed on 12 June for modifications. Attempts had been made to limit the number of people crossing the bridge, which led to long [[Queue area|queues]] but were ineffective to dampen the vibrations. Closure of the bridge only two days after opening attracted public criticism as another high-profile British Millennium project that suffered an embarrassing setback, akin to how many saw the [[Millennium Dome]].

The vibration was attributed to a then under researched phenomenon<ref>"Before the Millennium Bridge, the math of "synchronous lateral excitation"  from pedestrians was not at all well-understood. Once the bridge had been fixed, it was a well-investigated area." -- Humble Pi: When Math Goes Wrong In The Real World, by [[Matt Parker]], page 274</ref> whereby pedestrians crossing a bridge that has a ''lateral'' sway have an unconscious tendency to match their footsteps to the sway, exacerbating it. This is different from the well-understood problem of ''vertical'' sway, which is why troops stop marching in stride together as a unit when crossing such a bridge.<ref>{{cite book|last=Jeans|first=James|author-link=James Jeans|title=Science and Music|url=https://archive.org/details/in.ernet.dli.2015.459051|publisher=[[Cambridge University Press]]|year=1923|page=[https://archive.org/details/in.ernet.dli.2015.459051/page/n67 56]}}</ref> An example is London's [[Albert Bridge, London|Albert Bridge]], which has a sign dating from 1873 warning [[Military step|marching]] ranks of soldiers to break step while crossing.<ref>{{cite web|title=All troops must break step on Albert Bridge|url=https://www.flickr.com/photos/31505964@N08/6817075683/|url-status=dead|archive-url=https://web.archive.org/web/20140125215409/https://www.flickr.com/photos/31505964@N08/6817075683/|archive-date=25 January 2014}}</ref>