20 Things You Somehow Missed In Back To The Future Part 3
15. Doc References The Invention Of The Transistor
Early on in 1955, Doc reads his own 1885 letter aloud, including this passage:
"I set myself up as a blacksmith as a front while I attempted to repair the damage to the time circuits. Unfortunately, this proved impossible, because suitable replacement parts will not be invented until 1947."
Though it's hardly important to the story what Doc's talking about, he's actually referring to the point-contact transistor, which was invented by American physicists John Bardeen and Walter Brattain at Bell Labs in 1947.
As much as screenwriter Bob Gale could've just plucked a random year out of thin air, this once again shows the mind-boggling thought that went into every minute, basically insignificant detail.