How the Titanic Worked

As we've seen, the Titanic captured people's confidence. Ismay and Pirrie were confident that it would be the biggest and most luxurious ship in the world, thousands of passengers were confident that it would transport them to New York faster than any other ship could, and Capt. Smith was confident that the ship could withstand any of the innocuous ice floes he'd been warned of.

Now, Andrews, the ship's chief designer, was confident that the unsinkable Titanic would sink.

Titanic had earned the title of unsinkable from the watertight compartments in the ship's hull. We learned that doors between the bulkheads could be dropped to prevent flooding from spreading across all 16 compartments in the hull. The ship was designed to take on water in any two of the compartments and still sail on — Andrews said that Titanic could even tolerate flooding in a fourth compartment if necessary. But five flooded compartments mathematically guaranteed that Titanic would sink [source: RMS Titanic].

Let's recap now. Ships — even those made of materials as heavy as steel — float on the surface of water because buoyancy pushes them upward and gravity pulls them downward. These two forces balance each other out, allowing a ship to steadily float along.

In the case of the Titanic's compartments that we've been reading so much about, the air inside of them rendered the ship less dense than the surrounding water. But when the ship struck the iceberg, the lightweight air was quickly replaced by the dense water pouring into the damaged compartments. As a result, the ship's front (bow) became much heavier than the back (stern) and began a slow and steady descent downward.

The Titanic didn't just sink — eyewitness reports testify that it broke in half. Science supports these accounts. In the middle of the ship, the stress of bearing the heavy weight of the water-filled front compartments overwhelmed the steel structure. As the bow dipped beneath the waterline, the keel began to rise high out of the water and the steel plates holding this portion of the ship together started buckling under the pressure. This stress reached 35,000 pounds (15,876 kilograms) per square inch on the boat deck; that's nearly 50 percent more stress than the Titanic was designed to withstand. At last, the plates gave way. The bow plunged downward, and the ship snapped in two. When it severed, the flickering electricity was finally extinguished, and passengers and crew were left in the darkness of a moonless night.

Less than half would live to see the sunrise.