Have you ever seen a movie in which a building was burned down or a bridge was destroyed? Have you seen films in which a train crashed or a ship sank into the ocean? If so, you may have wondered how these things could happen without harming the people in the film. The person who knows the answer is the 'special-effects' person. He has one of the most important jobs in the film industry. In a scene for one movie there was a big glass bowl filled with the water in which small fish were swimming. The director of the movie wanted the fish to stop swimming suddenly while they seemed to stare at the actor. Then the director wanted the fish to stop staring and swim away. This was quite a challenge, since fish generally can't be forced to do anything. The special-effects person thought about this problem for a long time. The result was an idea for controlling the fish using of electricity. First he applied electricity to the fish bowl, causing the fish to be absolutely still. Then he rapidly reduced the amount of electricity, allowing the fish to swim away. Thus, he got the humorous effect that the director wanted without harming the fish. As in other parts of movie making, there are people who have developed particular skill in creating all kinds of effects. Jim White, who has been a special-effects specialist for thirty-two years, is best known for work with ships and airplanes. Calmly he builds and crashes airplane; or sends tiny models of ships on dangerous voyages. For a movie about World War Ⅱ, he built a boat which was a copy of a real ship. The copy was made of wood and was 165 feet long. As it sailed along at a speed of seven sea miles an hour in the Pacific Ocean, it seemed so real that a United States military airplane flew down near it, trying to discover which country owned it. All special effects production requires training, skill, and experience. It also can add a great deal to the expense of producing the film. The special-effects person's job is important because ______.