Since its opening more than 23 years ago, the Millennium Bridge has become one of London’s most iconic landmarks.
But tourists hoping to cross the famous crossing in the coming weeks will be disappointed.
It was announced this morning that the Millennium Bridge will be closed for three weeks for urgent maintenance.
It has acquired a reputation for being “shaky” as it swayed under the weight of thousands of pedestrians when it opened on June 10, 2000.
Here MailOnline reveals the science behind the 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 will be disappointed
It has acquired a bit of a reputation for being “rickety,” swaying under the weight of thousands of passers-by when it first opened on June 10, 2000. Here, MailOnline reveals the science behind this unusual phenomenon
Before 2021, scientists believed that bridges wobbled because people fell into step while walking, resulting in a synchronized pendulum effect.
But a study this year rejected this so-called Kuramoto model and instead suggested that bridges begin to sway when people walk at their own individual rhythm rather than copying each other.
Once these oscillations begin, each person tries to adjust their steps to avoid falling, which in turn destabilizes the bridge even further.
The theory was put forward by researchers at Georgia State University.
“Imagine passengers walking on a boat that is rocking back and forth in stormy seas,” said mathematician Igor Belykh of Georgia State University.
“They adjust their movement, both sideways and forward, to the vibrations of the boat.”
“In particular, they will slow their forward movement.”
The researchers said this transfer of energy from the steps to the bridge and the sway it causes is an example of negative damping, where small vibrations produce much larger end results.
They used the example of a rusty swing set in a playground and how it can eventually be made to move when enough people apply force to it.
To reach their conclusion, the scientists used observations of various bridge sway events, as well as modeling and other experiments.
The Millennium Bridge was used as the main example of the Kuramoto model. This is because video analysis showed that pedestrians’ heads and torsos moved as a unit
According to the data they examined, there was limited evidence of pedestrians walking in sync with one another.
The Millennium Bridge was used as the main example of the Kuramoto model.
This is because video analysis showed that pedestrians’ heads and torsos moved as a unit.
“This explanation was so popular that it was part of the scientific zeitgeist,” Belykh said.
However, Nobel laureate Brian Josephson was one of the first to question the synchronization explanation for the instability of the Millennium Bridge.
Another bridge swaying incident occurred in 2003.
A power outage on the east coast of the United States caused so many people to walk across New York’s Brooklyn Bridge that it began to shake.
Pedestrians said they felt seasick and had difficulty keeping their balance while standing still.
The researchers in this study found that bridges in general are likely more susceptible to vibration than previously thought.
The Millennium Bridge is known for its role in the 2009 film Harry Potter and the Half-Blood Prince
Now they want to analyze the movement of people in crowds in more detail to further support their theory that people’s naturally varying steps cause bridges to sway, rather than synchronized walking.
They also said that in the future, engineers may be able to calculate the threshold before a bridge begins to swing based on the number of pedestrians crossing it.
At the Millennium Bridge, for example, there are around 165 people.
Belykh said: “Bridge designers should be aware that dangerous cases of negative attenuation can always occur.”
“Our formula provides useful estimates given the expected number of pedestrians using a bridge.”