The flux capacitor is a fictional device created by Dr. Emmett Brown, and it is essential for time travel in the movie. It requires a significant power source, specifically a plutonium-powered nuclear reactor, to function. The DeLorean, a modified car, is designed to reach the necessary speed of 88 mph, which is a crucial plot point in the film. The sports almanac serves as a narrative device that illustrates the consequences of time travel, as it allows characters to manipulate events in the past to affect the future, highlighting the ethical implications of such power.