Wind, earthquakes, floods and fires — they can all be ferocious forces of nature. But if you judge purely on persistence, the award for the planet's strongest force would have to go to gravity. It's constantly trying to pull down everything that humans build up. That's why the Akashi Strait Bridge, with its record-setting main span of 6,532 feet (1,991 meters), is such an amazing engineering victory [source: Encyclopedia Britannica].
Completed in 1998, the Akashi Strait Bridge carries a six-lane road between the Japanese cities of Kobe and Iwaya. Everything about it is big: It stretches a total of 12,831 feet (3,911 meters) across three spans that are suspended from two towers measuring 975 feet (297 meters) in height. Given its location in a storm-and-earthquake-prone part of the world, engineers had to design it to withstand not only the forces of gravity, but 180-mile-per-hour winds and magnitude 8.5 quakes [source: WGBH]. This was accomplished by placing 20 tuned mass dampers in each tower. These large, suspended weights are designed to swing in the opposite direction of the bridge and essentially cancel out any sway it might experience. Still, don't expect nature didn't go down without a fight. Remember the 6,532-foot (1,991-meter) main span? It was originally designed to be 6,529 feet (1,990 meters) across, but while the bridge was under construction an earthquake moved the towers three feet farther apart! [source: Encyclopedia Britannica]