Since its opening more than 23 years ago, the Millennium Bridge has become one of London’s most famous landmarks.
But tourists hoping to cross the famous crossing in the coming weeks are in for disappointment.
This morning it was announced that the Millennium Bridge will be closed for three weeks for urgent maintenance works.
It has gained something of a reputation for being “wobbly”, as it swayed under the weight of thousands of pedestrians when it first opened on June 10, 2000.
Here, MailOnline reveals the science behind this unusual phenomenon.
Since its opening in 2000, the Millennium Bridge has become one of London’s most famous landmarks. But tourists hoping to cross the famous crossing in the coming weeks are in for disappointment.
It has gained a bit of a reputation for being “wobbly”, swaying under the weight of thousands of pedestrians when it first opened on June 10, 2000. Here, MailOnline reveals the science behind this unusual phenomenon.
Before 2021, scientists thought bridges wobbled because people caught up while walking, causing a synchronized pendulum effect.
But a study that year discarded the so-called Kuramoto model and suggested instead that bridges begin to sway when people walk at their own individual pace rather than copying each other.
Once these oscillations begin, each person attempts to adjust their steps to avoid falling, which in turn further destabilizes the bridge.
The theory was proposed by researchers at Georgia State University.
“Think of passengers walking on a ship rocking from side to side in a stormy sea,” said mathematician Igor Belykh of Georgia State University.
‘They will adapt their movement both laterally and forward in response to the movement of the boat.
“In particular, they will slow down your progress.”
The researchers said this transfer of energy from the footprints to the bridge, and the sway it causes, is an example of negative damping, where small vibrations cause much larger end results.
They used the example of a rusty swing on a playground and how it can eventually be made to move if enough people apply force to it.
The scientists used observations from several bridge sway events, as well as modeling and other experiments to reach their conclusion.
The Millennium Bridge was used as the main example of support for the Kuramoto model. This is because video analysis showed the heads and torsos of pedestrians moving together as one.
From the data they observed, there was limited evidence of pedestrians walking in sync with each other.
The Millennium Bridge was used as the main example of support for the Kuramoto model.
This is because video analysis showed the pedestrians’ heads and torsos moving together as one.
“This explanation was so popular that it has been part of the scientific zeitgeist of the time,” Belykh said.
However, Nobel laureate Brian Josephson was one of the first to question the timing explanation for the Millennium Bridge instability.
Another bridge sway incident occurred in 2003.
A blackout on the east coast of the United States caused so many people to walk on New York’s Brooklyn Bridge that it began to shake.
Pedestrians said they felt dizzy and struggled to keep their balance while standing still.
The researchers in this study found that, in general, bridges are likely to be more vulnerable to oscillations than previously thought.
The Millennium Bridge is known for appearing in the 2009 film Harry Potter and the Half-Blood Prince.
They now want to carry out more analysis of the movement of people in crowds to further support their theory that people’s naturally varying steps cause the bridges to sway, rather than walk synchronously.
They also said that in the future engineers will be able to calculate the threshold before a bridge begins to sway based on the number of pedestrians crossing it.
For example, for the Millennium Bridge there are about 165 people.
Belykh said: ‘Bridge designers must be aware that there can always be dangerous cases of negative damping.
“Our formula provides useful estimates, given the expected number of pedestrians using a bridge.”