"Anachronisms are the most common and most insidious disease of science fiction and fantasy. They can take many forms, popping up at all the least convenient times, and sometimes leaving authors and editors scratching their heads over how to fix ones they have found or how to apologize for ones discovered by readers. An anachronism is an unintentional mistake in chronology...two fun examples: The space shuttle Dr. Floyd takes to the space station in 2001: A Space Odyssey is operated by Pan Am, an airline that went out of business in 1991. Stephen King’s The “Green Mile” is set in the fictional |Cold Mountain Penitentiary in Louisiana in 1932, and prominently features death row inmates executed by means of the electric chair. But the electric chair was not used in Louisiana until 1941."