On June 10, 2000, Londoners celebrated the technological promise of the new millennium with the opening of a state-of-the-art pedestrian bridge over the Thames River. Two days later, the Millennium Bridge was vibrating so intensely that it was closed and did not reopen for more than two years. Explore the phenomenon of synchronous lateral excitation and learn how engineers were able to fix “The Wobbly Bridge†and develop methods to prevent similar failures in other bridges.