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Titanic Disaster, one of the worst maritime disasters in history. The luxury liner Titanic (46,000 gross tons) on its maiden voyage from Southampton to New York City struck an iceberg about 153 km (about 95 mi) south of the Grand Banks off Newfoundland just before midnight on April 14, 1912. Of the more than 2,220 persons aboard, about 1,513 died, including the American millionaires John Jacob Astor, Benjamin Guggenheim, and Isidor Straus. The Titanic sailed under British registry as part of the White Star Line, which was owned by a United States company controlled by the financier J.P. Morgan.

The ship had been proclaimed unsinkable because of its 16 watertight compartments. Nevertheless, the iceberg sufficiently damaged the Titanic to make it sink in less than three hours. Subsequent investigations found that the ship had been steaming too fast in dangerous waters, that the captain had ignored radio transmissions warning of ice, that lifeboat space had been provided for only about half of the passengers and crew, and that the Californian, close to the scene, had not come to the rescue because its radio operator was off duty and asleep. These findings led to many reforms, such as lifeboat space for every person on a ship, lifeboat drills, the maintenance of a full-time radio watch while at sea, and an international ice patrol.

The sinking of the Titanic has been the subject of several books and films, including the Hollywood blockbuster, Titanic (1998). It was not until September 1985 that the actual wreck was found resting under about 3,800 m (about 12,000 ft) of water. The area was photographed by a joint French-United States expedition through the use of robot submersibles equipped with television cameras (see Deep-Sea Exploration, Submersible Craft). In July 1986 the U.S. researchers, led by American deep-sea explorer Robert Ballard, explored the Titanic in the three-person Alvin submersible; they took pictures of the interior, but recovered no artifacts. The following year a controversial French salvage effort retrieved dishes, jewels, currency, and other artifacts, which were exhibited in Paris in September 1987 and in Hamburg in 1997. In August 1998 a substantial section of the ship’s outer hull was recovered from the sea floor. Surveying and investigation of the wreck continues.

Although these visits brought back haunting photographs and artifacts, no one had ever been able to thoroughly assess the damage caused by the Titanic's collision with the iceberg. Historians had long thought the sinking of the vessel resulted from massive damage to the ship's steel hull. Experts have since found evidence, however, that it was the location, rather than the extent, of the damage that caused the ship to sink. An expedition in August 1996 set out to examine the wreckage and to locate and study the damage to the hull. Sonar experts, naval architects (including one from the shipyard that built the Titanic), a microbiologist, and historians of the shipwreck were among the experts accompanying the expedition. The purpose was to determine whether the ship broke apart on the surface, to what extent flaws in the steel used to build the Titanic's hull contributed to the disaster, and how long the wreck is likely to survive on the ocean floor. The expedition also attempted to raise a 28 sq m (about 300 sq ft) section of the Titanic's hull, but a storm and a broken rope sent the piece plunging back to the ocean bottom.

According to the 1996 expedition's experts, the bow portion of the Titanic had struck the seabed at an angle and slid across it, plowing up sediments that covered the damaged area of the hull. To overcome this obstacle, the 1996 expedition used sophisticated sonar equipment, known as a sub-bottom profiler, to determine the extent and nature of the damage. Sonar uses reflected sound waves instead of light waves to “see” objects. Because sound waves can both penetrate material and reflect off material of differing density in different ways, the sonar was able to provide an image of what lay behind the sediments.

The Titanic was considered practically unsinkable because its hull was divided into 16 watertight compartments. The ship was designed to stay afloat with any two adjacent compartments or the front four compartments (which were smaller in volume) flooded. As a result, many authors of books on the disaster thought that only a huge tear, perhaps 90 m (300 ft) long, could have caused the 269 m (882 ft) ship to sink. But Edward Wilding, a naval architect, testified in the wake of the disaster that the total area damaged by the iceberg was small and probably did not exceed 1 sq m (about 12 sq ft). Others, however, did not believe that so large a ship could be undone by so little damage, and so the myth of the huge gash began. Previous expeditions found no sign of a gash, however, and the latest sonar findings confirmed Wilding's belief that the damage was slight: six thin breaches spread out along a 35 m (110 ft) section of the hull with a total surface area of about 1 sq m (about 12 sq ft). The ruptures punctured six watertight compartments and were spread strategically along riveted seams.

A 1991 expedition had also retrieved samples of the Titanic's steel for analysis. Tests determined that the steel's poor resistance to impact, a quality known as impact strength, combined with its chemical makeup, made the steel brittle. This problem was compounded by the fact that the Titanic was operating in unusually cold waters for that time of year. When exposed to near-freezing temperatures, tests showed that the steel became extremely brittle. The August 1996 expedition confirmed these findings and applied them to the question of whether the Titanic broke apart before sinking.

At the time of the Titanic's sinking there were conflicting reports as to whether the ship broke up at the surface or sank intact. All of the ship's surviving officers said the Titanic sank intact. A number of passengers, however, said that the ship broke up at the surface. Earlier expeditions established that the ship was in two pieces on the ocean floor, but some experts had theorized that the ship broke up on its way to the bottom. There was even a claim that there might be a third piece.

Based on the new findings about the nature of the damage sustained by the Titanic and the quality of the steel used in the hull, naval architects set out to determine the stresses that might have prevailed as the ship sank. The architects used a computer simulation of stresses in the hull, known as a finite element model. The simulation showed that the weight of the waterlogged bow would have generated enough stress to cause failures in the Titanic's steel plates as the ship sank, confirming reports that the ship broke apart before sinking. Also, the 1996 expedition located a third piece of the ship, indicating that the ship broke in two places.

Another series of tests performed in 1998 on some iron rivets brought back from the site found excess amounts of slag, a metal waste product added in small amounts to give iron strength. However, too much slag makes iron brittle, and there is evidence that weak rivets may have also contributed to the ruptures.

Great forces conspired to sink the Titanic, but scientists found that tiny ones will cause it to collapse and eventually disappear. In the 85 years since the Titanic sank, iron-eating microbes have slowly sapped the strength from the Titanic's structure. Eventually the wreck will no longer be able to support its own weight.

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