How did a steel ball protect Taiwan's tallest building during the 7.4-magnitude earthquake?

A large yellow pendulum at the centre of Taiwan's tallest building, Taipei 101, helped protect it from the recent 7.4-magnitude earthquake. Known as "tuned mass damper", the 660-metric-tonne steel sphere is suspended between several floors at the top of the building. The sphere moves back and forth during earthquakes or typhoons, absorbing the force of any violent swinging.