Taller Than Physics Wanted

The Burj Khalifa stands 828 meters tall — more than twice the height of the Empire State Building. At that altitude, engineers faced a problem skyscrapers usually shrug off: the building sways. Strong winds can nudge the tip more than a meter off center, enough to make people inside feel queasy if nothing is done.

The fix is built into the shape. A Y-shaped footprint spreads three wings around a central spine, and a buttressed core ties them together so the tower resists twisting. Each wing braces the others, turning a slender tower into a rigid one.