Wednesday, July 25, 2012

Andrea Doria

On July 25, 1956 the ocean liners Andrea Doria and Stockholm collided near Nantucket. Fifty-two passengers and crew members on the two vessels died and hundreds were injured. Eleven hours after the collision, the Andrea Doria sank to the bottom, where she remains today.

More than forty years after the Titanic sinking, the lessons learned in that earlier disaster were incorporated both into the design of the Andrea Doria, and in the response of her crew when the collision occurred. The collision made half the lifeboats on the Andrea Dorea unusable or inaccessible, but more than 1600 passengers and crew members were rescued and survived. Watertight compartments were properly secured, unlike in the Titanic incident, giving rescuers time to get most people to safety. Of the 52 dead, most had died in the initial collision.

There was no formal finding of fault. The two shipping companies that owned the Andrea Doria and Stockholm reached out of court settlements with each other and survivors, so no legal determination was ever made. An initial inquiry placed most of the blame on the officers of the Andrea Doria for improperly maneuvering their vessel in the minutes before the collision. Later investigations point to the Third Officer of the Stockholm and his misuse of a new technology called radar.

In the study of human error, fixation is the tendency to focus on one or two inputs when things get stressful. Fixation has been a factor in industrial accidents like the one at Three-Mile Island nuclear plant, in aircraft crashes, and in maritime accidents. In the Andrea Doria incident, many believe the Stockholm’s Third Officer was so focused on his radar that he not only ignored other sources of information, he didn’t even notice the radar was set at a different scale then he believed it to be: the Andrea Doria was only five miles away; he thought she was twelve.

Following the collision, radar set designed was improved to make such mistakes less likely, and radar training requirements for bridge officers put into place.

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Saturday, July 21, 2012

Capt. Cook & The Transit of Venus

Photo of the 1882 transit, which revealed a precise distance for Venus's orbit.

Last month’s transit of Venus across the face of the sun was largely an astronomical curiosity, but a similar transit in 1769 held great potential for expanding our knowledge of the universe. By comparing observations made from several points throughout the world, scientists hoped to measure the true size of the orbit of Venus, and thus the orbits of the other planets, and thus the size of the Solar System. Playing a key role was a captain named James Cook.

Statue of Cook
in Greenwich
In 1716, Edmond Halley (he of comet fame) published a paper explaining how a transit of Venus could be used to make the necessary calculations. Halley was more than the scientific father of the 1769 expedition, though. He also commanded an expedition in 1689 to measure compass variations. Halley was so bad a commander that the Royal Navy refused to allow a scientist to command one of its ships ever again. Thus Cook, a gifted mathematician and cartographer as well as a naval officer, was selected to lead the expedition.

A civilian collier, the Earl of Pembroke, was selected as the vessel for the expedition. Its shallow bottom and sturdy construction made it ideal for the voyage in ways a traditional warship would not be. The ship was overhauled, armed, and commissioned Endeavour. In August 1768 the expedition set out for Tahiti, where Cook and two scientists on board would make independent observations. It arrived the following April, and Cook made good use of the weeks leading up to the June 3 transit to build an observatory.

The results were disappointing,. The three sets of measurements taken at Tahiti did not match up within the margin of error, due to an optical phenomenon called the “black drop effect.”  Combined with measurements from more than a dozen other sites around the world, scientists were able to refine the estimates for the size of Venus’s orbit, but not with the degree of precision they had hoped for.

Cook’s voyage of exploration was not over yet. After the transit, he opened sealed orders instructing him to find and claim Terra Australis Incognita, a large southern continent of supposed great riches. He never found it and, indeed, did not believe it existed in the first place. The Endeavour did visit New Zealand and Australia and Cook was able to determine that the latter was a separate continent (it was previously believed to be part of New Guinea).

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