a electrical capacitor capable of storing the 1.21 gWe generated by a nuclear reaction, or lightning bolt. Unique due to its size, as conventional capacitors that can handle such energy would take up the space of a small apartment complex. The device has nothing to directly with time travel, merely allowing the 1.21 gWe to be used all at once, and in phase.
"And that's when you came up with the idea for the Flux Capacitor...
Which... is what makes time travel possible." - Marty McFly
In the, "Back to the Future," series, a device that, when installed into a moving vehicle that can move at or above 88 miles per hour, allows a person to travel through time. The classic case of such a time travelling vehicle is the Delorian.
Dr. Emmet Brown struck his head in the bathroom only to find that he had come up with the idea for a Flux Capacitor