Amy Jacobson, age 10, of New Hartford, N.Y., for her question:
WHERE IS THE WORLD'S LONGEST BRIDGE?
Near Moab in the state of Utah is the world's longest natural bridge. Called the Landscape Arch in Arches and Canyonlands National Park, it stretches 291 feet and is located about 100 feet above the canyon floor. In one spot, erosion has narrowed one section to only six feet thick. Rainbow Bridge, also in Utah, is 278 feet long.
We have proof that man was building bridges as far back as 3200 B.C. There was one in Sumeria at that time, and one over the Nile in 2560 B.C.
Early bridges weren't too long, but by 1899 a covered bridge measuring 1,282 feet was built in Hartland, New Brunswick, Canada. A cantilever bridge 1,800 feet long came along in 1917 to break the record with the Quebec Railway bridge in Quebec, Canada.
Longest single span suspension bridge in the world today is the Verrazano Narrows Bridge which goes across the entrance to New York Harbor. The $305 million masterpiece was started on Aug. 13, 1959, and opened to traffic on Nov. 21, 1964. The graceful structure connects Staten Island and Brooklyn and measures 6,690 feet between anchorages. It carries two decks, each holding six lanes of traffic.
Verrazano Narrows has a center span of 4,260 feet. The tops of the two main towers, each 690 feet tall, are just under two inches out of parallel to allow for the curvature of the earth.
Having a main span of 3,800 feet with 8,344 feet between anchorages is the Mackinac Straits Bridge between Mackinaw City and St. Ignace, Mich. It opened in 1957 and cost $100 million. The San Francisco Golden Gate bridge, completed in 1937, has a main span of 4,200 feet, just 60 feet less than that of the Verrazano Narrows.
In 1979 there will be a new record holder. The Humber Estuary Bridge in England, which will have a main span of 4,626, was started in 1972 and will cost more than $100 million.
And in 1988 watch for the opening of a double deck railroad bridge linking Hinshu and Shikoku in Japan. This huge structure will be 5,840 feet in length over its main suspension span, with its total length measuring 11,680 feet.
Longest steel arch bridge in the world is the New River Gorge bridge near Fayetteville, W. Va., which measures 1,700 feet in length.
Longest floating bridge in the world is the Second Lake Washington Bridge in Seattle, with a length of 12,596 feet and a floating section measuring 7,518 feet.
Longest railroad viaduct in the world is the Great Salt Lake Viaduct in Utah, which carries the Southern Pacific Railroad across 11.85 miles of the. Great Salt Lake. It opened in 1904 as a pile and trestle bridge and then converted to a rock fill structure between 1955 and 1960.