Flux Capacitor

Lore & Background

During the development of Back to the Future, the creative team initially conceived a laser device attached to a refrigerator for time travel. Director Steven Spielberg vetoed this idea due to safety concerns that children might climb inside and get trapped. Robert Zemeckis suggested using a DMC DeLorean because its mobility solved the stationary problem, and its gullwing doors would appear like an alien UFO to a 1950s family. When deciding on origins, the team chose an eccentric individual named Doc Brown building it in his garage rather than a corporation, which Bob Gale felt gave it a "slapdash, kind of cool look." The component was originally called the Temporal Field Capacitor, but Zemeckis found the name unbelievable. Michael Fink, drawing on his work with neutron flux from The China Syndrome (1979), and Zemeckis simultaneously suggested renaming it the Flux Capacitor. Cobb and Probert had already placed this device on the external and interior roof of the DeLorean, but Fink moved it next to the driver.

In Their Own Story

The construction of the physical device was a hands-on process led by Michael Fink, who built the unit using a NEMA box and backlit Torr High-Voltage relays. The time display elements were constructed from LMB boxes. Fink later picked Michael Scheffe as his replacement; Scheffe finished the Flux Capacitor build and also constructed the "Mr. Fusion" replacement power supply out of a Krups coffee grinder. In the film's narrative, the device requires exactly 1.21 gigawatts of electricity to function. This massive power requirement drove plot points where the energy source shifted from a nuclear bomb test in the Nevada desert to lightning striking a clock tower in Hill Valley due to budget overruns and scheduling issues during filming.

Reader's Guide

To operate the time travel mechanism, two specific conditions must be met: the vehicle must reach a speed of 88 miles per hour (142 km/h), and the system requires 1.21 gigawatts of electricity. The choice of 88 mph was made because it was easy to remember and looked "cool" on the speedometer. However, building a custom speedometer was necessary because a 1979 law passed by President Jimmy Carter had limited commercial vehicle speedometers to 85 mph. The device's internal workings rely on the specific placement of the Flux Capacitor next to the driver, distinct from earlier sketches that placed it on the roof. The component is so integral that without the required power and speed, the DeLorean cannot breach the temporal barrier.

Did You Know?

• The component was originally named the 'Temporal Field Capacitor' before Michael Fink and Robert Zemeckis simultaneously suggested renaming it the Flux Capacitor.
• Michael Scheffe constructed the 'Mr. Fusion' replacement power supply using a Krups coffee grinder.
• A 1979 law by President Jimmy Carter limited speedometers to 85 mph, necessitating a custom build to simulate 88 mph on screen.
• Cobb and Probert initially placed the Flux Capacitor on the external and interior roof of the DeLorean before Fink moved it next to the driver.