Originally Posted by Spengler56
I thought Mr. Fussion was essentially a car battery? Would it have enough juice for the required 1.21 gigawatts. By the way, I thought it interesting how the time machine still supposedly ran on gas in part 3, even though Doc says "I need fuel" when he puts trash in it at the end of part 1.
It would create a paradox if Marty and Doc were stuck in 2015, though it's hard to say if Biff would know that. Does this mean the Alamac would have disappeared back in 1955 had Doc and Marty been stranded in 2015?
Nobody knows what would happen if a paradox happens. Or maybe it does as we've seen instances of time travel with the direct intent on changing the timeline (doc and marty going to 2015 in part II, biff going to 1955 and doc and marty going to 1955).
And mr fusion is a replacement for plutonium for the time circuits, theres plenty of instances showing this; as mentioned the plutonium is only enough to power one time travel. But we never see plutonium put in the delorean before the trip to 2015, biff wouldnt be able to get a hold of plutonium in 1955 to get home, and marty wouldnt be able to get plutonium in 1955 to get to 1885 or 1885 to get home.
It's assumed what doc means at the start of part I is that the time circuits are electrical. In part 3 he does state that the car itself runs on gasoline and prior to sending him back to 1885, 1955 doc does tell marty he put fresh gas in the tank.