Originally Posted by Spengler56
I think you raise a good point of how Biff would know how to use the time machine. How would he know to go 88 MPH or that he needs to load plutonium? Then again he had all the time he needed to figure it out since he has a time machine.
Like many sci fi movies there are plenty of holes you can pluck. For example, why did Biff return the time machine to Doc and Marty? I would have thought he would return it in a different place or time where they couldn't find it and he wouldn't have to worry about Marty and Doc coming after him. Also, I don't understand how old Biff would not return to the the hell Hill Valley of 2015. Shouldn't the world have changed for Doc and Marty after biff jacked the time machine?
Prior to mr. fusion, the delorean needed plutonium for each time travel. It may be possible that with mr fusion, the delorean can time travel multimate times for each time travel. I'd assume that it either had enough to time travel already or perhaps Biff new what mr. fusion was and how to use it. I dont think it is labelled that the delorean must go 88 mph but maybe biff just figured it has to go fast to time travel and eventually got it to 88 mph.
I'm not sure if old biff is smart enough to figure this out but if he did not return the delorean to doc and marty, it would cause a paradox or at least prevent him to get rich; Doc and Marty go to to get Jennifer from her future home and go to the future in the first place to due to their future children. If Marty and Jennifer got stranded in the future, they wouldnt have children there and thus doc would never bring them there in the first place for biff to steal the time machine.
Another potential is that Biff started having his 'symptoms' that we see while in 1955 and that is why he goes back to the future.
Biff specifically remarks to himself "doc brown invented a time machine" and pieces together that one of the 2 "Marty Jrs" he sees is Marty Sr. from the past so he figures when they find out the timeline has changed, they'd come asking him about the almanac.
Now one thing I've wondered; Biff sees the delorean fly and 'disappear' in 1985, the next day he sees marty (after returning from 1885), why wouldnt he ask him what on earth happened? Didn't they wonder where marty went to without his truck? Not sure how those 2 timelines would play out in their eyes as Marty leaves 1985 around 11 am on the 26th, returns to the alternate timeline at 9 AM on the 26th, leaves around 2 AM on the 27th and returns at 11 AM on the 27th.