The theory: a cargo ship with a "dirty bomb" was just outside of Charleston, South Carolina. The notion came to life during a live YouTube broadcast Wednesday evening. During the broadcast, conspiracy theorist George Webb initially claimed a "source" had told him that there was "a dirty bomb planned for a major city." Based on the information from the "source," Webb said he believed Memphis might be the target. The Coast Guard said in a further statement provided to CNN that the source of the threat had been detained by authorities for further questioning. The statement did not mention Webb's...