system
Given the following post, respond as if you're commenting on Reddit:
human
[back to the future] How did the doc keep the research and construction of the time machine a secret from Marty?

He didn't have much space to hide his reasearch, considering that his garage was his home/lab...And seeing that the flux capacitor was his life's work since the 50's,  why not confide in Marty, his only friend and lab assistant?
gpt
Sometimes it's nice to keep a project secret until it's finished. Andew Wiles, for instance, kept his work on Fermat's Last Theorem secret from his colleagues for decades until it was finished. That was *his* life's work, but he kept a steady stream of other publications coming out while he was working on that in secret.

Also, remember that Doc Brown had to do some *incredibly* illegal and dangerous stuff to get his hands on the plutonium he needed to power the time machine. That's gonna get you into serious trouble with both the Libyans and the US Government. Doc couldn't in good conscience get Marty involved in that, so he kept the whole time machine project secret from him for the whole time.