Reducing building vibrations due to wind and earthquakes in tall buildings is one problem that must be addressed by structural engineers. There are various ways of doing this. One method is by installing passive and active dampers. When I visited Taipei 101 in 2007, I was introduced to “Damper Baby,” – the name given to one of the dampers installed at the currently world’s tallest building. Taipei 101 has a total height from the ground to the spire of 509 m. It has 101 stories above ground and five underground. In designing the tower, engineers had to consider the fact that " it will stand about 650 feet from a major fault line, and that it will face winds of 100 mph." Deflections resulting from extreme wind loads and earthquakes will be minimized by "three separate tuned-mass dampers: a primary, low-frequency 635,000kg damping sphere almost 6m in diameter formed from 41 layers of 12cm thick steel is suspended between the 92nd and the 88th floor to counter overall tower sway, while two smaller, higher-frequency dampers 7 tons in weight are installed inside the 20 m tall mast to counter mast vibrations. " The damper can reduce building vibrations by as much as 40%. Another technology of reducing vibrations is by the use of active control systems. Taipei 101 has also active control systems which eliminate vibrations. The video below is an exhibit at Taipei 101 showing the effect of active control systems in buildings.