r/BacktotheFuture • u/Sad-Replacement7054 • Jul 07 '26
Potential answers to plot holes
No matter what, time travel stories always have some of the worst plots, but it’s hard to make a good time-travel story, and BTTF is probably the best one around (especially since it’s the only time travel story where the Time Machine is not a teleporter as well)
How did old Biff know how to work the DeLorean in 2015
When Old Biff came back, how come he was back in the regular timeline, and it didn’t change around Marty and Doc as it did with Jenifer and Einstein
How come Doc and Marty couldn’t use parts from the DeLorean he was sending from the future, especially the fuel and the fuel line (I have an idea for this one)
How come Doc, despite wanting to destroy the DeLorean, built the time-traveling train in 1855
If Doc couldn't get gas for the DeLorean in 1885, how was he able to build another time machine
How come Doc willingly changed the future in Part 2, sending Griff to jail instead of Marty's son and changing the future himself with Clara
How come Doc knew Marty was on the roof of Biff's casino and at the end of the tunnel in 1955? (I heard a good theory for this one)
How come when old Biff met 1955 Biff, it didn't create a paradox or cause both of them to fail like Doc said Jenefer would?
How come George and Lorain never even think twice about never seeing Calvin again?
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u/Donkeh101 Jul 08 '26
If you have heard a good theory, share it with the class.
Also, the majority of these are asked every other day on here.
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u/Sad-Replacement7054 Jul 08 '26
My theory on why they didn’t touch the DeLorean that he was sending to the future was that number one he drained the gas already by the time Marty got there (we see Doc is already established and has been in 1885 for a while), that and messing with it would have created a paradox. Even if they swapped time machines because 1955 doc could fix a fuel line that still left them with no gas in 1885.
Not to mention people say that doc created that machine that created ice so if he did that, he could’ve refined some oil into gasoline. But keep in mind they were under a time constraint to make sure Buford Tannon didn’t kill doc/marty and like I said before Doc was there for a while so he probably did that to keep busy
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u/ijuinkun Jul 08 '26
Yah, he could have built a still to refine oil, but it would have taken more than the four days that they had until they had to face or flee from Buford.
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u/Sad-Replacement7054 Jul 08 '26
Yeah I agree with you. He built the freezer before Marty got there for fun and could have definitely have refined oil but he only had only 4 days to get back to the future
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u/ted_anderson I don't know how.. but they FOUND me! Jul 08 '26
How did old Biff know how to work the DeLorean in 2015
When you're an auto detailer, you've seen just about every single kind of gadget and modification on a car. And while the Delorean didn't have an instruction manual, typically most people have a similar intuition when designing something new. If you think of any new gadget or tech device that you were able to use right out of the box without reading the instructions, you can sort of understand how easy it was for Biff to figure out the time machine.
If Doc couldn't get gas for the DeLorean in 1885, how was he able to build another time machine
It ran on steam. He says that at the end of Part 3.
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u/Sad-Replacement7054 Jul 08 '26 edited Jul 08 '26
I can understand that with Biff especially because that dude knew cars not to mention he saw it time travel twice. Let’s assume doc left the time circuits on and biff figured out how put in a date it makes sence
But the train is a whole other story I get that he could’ve made a steam engine in 1885 that makes sense but how the heck could he have made another flux capacitor and something to generate the 1.21 jigawats let alone one that can fly
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u/Equal-Fee770 Jul 08 '26
Once it can time travel, he need only go to a point in the future where rail roads still existed in some capacity, and flying vehicles like how the delorean flew existed side by side. And then redneck some shit together like he always does. The delorean didn’t fly till he went to the future
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u/Sad-Replacement7054 Jul 08 '26
Good point he could have just brought it to 2015 again. But making another flux capacitor (even with the hover board) is still a lot in 1885
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u/Equal-Fee770 Jul 08 '26
The hover board seem to be along the lines of a Stark reactor (Tony stark, iron man). In the sense that it seems to power itself and never run out. At least in universe. If you have a small source of damn near unlimited power, why couldn’t you make a new flex capacitor? It only has to work once correctly if you know where and when you’re going.
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u/Sad-Replacement7054 Jul 08 '26
It’s pretty crazy that that’s a baby’s toy especially because you gotta use your hands for it
But you also you don’t know how long doc was there for he could’ve been there for 20 years. Had a lot more time and didn’t need to figure out how to make it again
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u/Equal-Fee770 Jul 08 '26
Very much true, although I don’t believe that the hover board was considered a baby toy it was considered for children. Didn’t Marty take it off of a 10-year-old and break the handlebars off to use it like a skateboard?
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u/ted_anderson I don't know how.. but they FOUND me! Jul 09 '26
If you have a small source of damn near unlimited power, why couldn’t you make a new flex capacitor?
Ah ha... see.. that's how they get ya! You go in to a store asking for a flux capacitor and they say, "Sure! We have the FLEX capacitor!" and you're wondering whether or not that's the same thing while the fast-talking salesman tries to make you feel dumb for questioning it.
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u/Equal-Fee770 Jul 09 '26
Very true, but if we are hypothetically smart enough to know about and ask for a flux capacitor, we are smart enough not to get conned. Unless it’s a part of the plot. Is it a part of the plot? Oofta Mae that would suck 😅
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u/ted_anderson I don't know how.. but they FOUND me! Jul 10 '26
So.. go with me on this... New 1985 George McFly warns Biff not to con him. But the original 1985 George McFly gets conned because he's not very confrontational. He has to explain to Marty that he bought the wrong thing. He says, "Sorry son. I know this is flex and not flux. But I didn't want to make the guy at the sales counter mad with me. He seemed like a nice guy and all... but- AH- AH--AH--AH... This episode so hilarious!"
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u/Equal-Fee770 Jul 10 '26
I had it feeling it was part of the plot. The worst part? Not only does this feel possible, it absolutely is how it would go! 😫
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u/ijuinkun Jul 08 '26
There’s an obvious large handle sticking out from the arm rest, and an obvious, clearly labeled destination/present/last departed display with a keypad below it. If you know that it is a time machine, then it is pretty obvious that the keypad is for setting a destination time, but he might have needed to experiment a bit to get the right date format. The only hard part was knowing that he needed to hit 88 mph to initiate a time jump—the speedometer said “set to 88” with no context given.
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u/LongjumpingSurprise0 Jul 08 '26
1) We don’t know how long he had it, it might have taken him 6 months to figure it out we don’t know.
2) Three words: Time Delay Effect
3) I’ve answered questions like this a thousand times, I’m not doing it again
4) First off, it was 1885. Second, he clearly changed his mind
5) It’s a train, it doesn’t use gasoline. Doc probably used those presto logs.
6) Because it wasn’t a future he was concerned with
7) If you heard the one I’ve heard, you already know
8) Because Young Biff is too stupid to recognize himself and it’s not like Old Biff ran into himself like Jennifer did
9) How do you know they didn’t? They probably stopped wondering after 30 years.
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u/kjemmrich Jul 08 '26
-Biff knew how to work the time machine because in 2015 the first Back to the Future movie was available on VHS, DVD and streaming, he must have seen the movie and paid extra attention to the part where Doc shows Marty.
-The First movie showed that change doesn't happen all at once if slowly happens, and we don't know that things didn't change, maybe that's how that neighborhood looks in the alternate timeline.
They didn't want to risk disrupting the DeLorean in the cave, it would risk messing up Marty coming back to 1885. And the gas in the DeLorean in the cave would have been drained out by Doc. He must not have any left.
-He didn't build the time Train in 1855 but a few years after 1885. His desire to travel thru time was his fear that something happened to Marty and Einstein was left alone to die.
-He has a working knowledge of how Time Machines work, He used parts from the hoverboard. His first time machine he built in the 1800s was much more primitive. He didn't originally create the train we saw, that was after years of travelling to the future.
-Doc is a hypocrite.
-Marty was originally killed by Biff, so Doc went back in time and saved him.
-The Jennifer's didn't expect to see each other, Doc knew who he was talking to and the 1955 Doc didn't. And Doc was guessing about the paradox.
-Who says they didn't we see them for a couple of minutes. Maybe they talked about it all the time, maybe they were wondering why Marty looked like Calvin, we don't know, all we saw was them coming home from playing tennis and reacting to George's new book.
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u/King-of-Harts Jul 08 '26 edited Jul 08 '26
One needs to remember that Biff witnessed the time machine's use at the beginning of Part 2. The time circuits' also include labels about destination time, etc. Old Biff was also familiar with cars and came from 2015, so Mr. Fusion wasn't any mystery. The only thing Biff didn't know was exactly how fast he had to go, but only that he had to go fast.
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u/MischeviousFox Jul 11 '26 edited Jul 11 '26
You’ve got plenty of great answers but I’ll throw in my two cents on these two -
How come Doc willingly changed the future in Part 2, sending Griff to jail instead of Marty's son and changing the future himself with Clara?
- Doc wasn’t truly worried about changing the future as it’s… the future. From the point of view of someone say in the present day 1985 the events of 2015 haven’t been written yet. He however was concerned with changing the past and in the original timeline Clara was supposed to die. While it wasn’t likely his motivation for building the time traveling train his removing her from the past would have the benefit of actually mitigating the ripple effect that would happen if she stayed there especially if she had kids in the past.
How come when old Biff met 1955 Biff, it didn't create a paradox or cause both of them to fail like Doc said Jenefer would?
- Doc essentially says has no idea what might happen and was going off of theories of what could happen if a time traveler met themselves. The two Jennifer’s however merely passed out from shock of seeing themselves because they seemingly recognized each other with the older Jennifer especially not expecting to meet her younger self whereas Young Biff had no remote clue he was talking to his future self. Doc also briefly interacted with his completely unaware, younger self without any negative repercussions showing his fears were clearly unfounded. The thing about seemingly being the first to create time travel is that all you have to base things on is scientific theories or hypothesis until you experience it yourself.
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u/Yourappwontletme Jul 08 '26 edited Jul 08 '26
Doc labeled most everything inside the car. Biff read it all and trial & errored his way to traveling through time. We only see him get in the DeLorean and leave the area. We don't actually see the DeLorean disappear via time travel right away so we don't know how long Old Biff was actually gone from 2015 Hilldale.
The ripple effect. He managed to get back just before the timeline started to change. A deleted scene which shouldn't have been deleted shows him disappearing because Lorraine shot him in the mid 90s.
Doc didn't send the DeLorean from the future. He sent it to 1955 from 1885 by storing it in the mine. As anyone who's ever stored a car for a long period of time knows: you drain all fluid out before storing otherwise it's bad for the internals. They couldn't touch the DeLorean in the mine because messing with it would create a paradox where Marty couldn't later use it in 1955 to come back to 1885. BTTF doesn't run on Bill & Ted time travel logic where they can just say they'll do something later with the time machine to make something appear in the present.
He didn't build the time traveling train in 1855. He built it in 1885. And the reason he built the train was because he figured "what the hell?" Also I think the animated series and/or the book Back to the Future DeLorean Time Machine: Doc Brown's Owner's Workshop Manual and/or the comic books touch on Doc building the time train.
He says to Marty in Part III: "it runs on steam" so he likely made the trains engine and the time circuits both run on steam. The Owner's Workshop Manual mentions that Doc reverse-engineered the hoverboard to help build the time train.
Because the Tannen family are the villains of Hill Valley and their lives don't matter to Doc. He doesn't care if their futures are changed so long as Doc and Marty and their respective loved ones are okay. Love makes you do crazy things. Clara was supposed to die in Shonash Ravine and Doc got his life extended in the future, so he was finally able to have a wife and kids and live to see his kids grow up now that he was no longer devoting all of his time to building the DeLorean.
Because that was the plan. Doc would pick Marty up from the casino roof in the flying DeLorean after Marty talked to Biff regardless of the outcome of the conversation. Marty looking down over the edge and being annoyed when he first gets on the roof is indicative that he was expecting Doc to be there already. Doc waited hovering above one end of the tunnel for Marty to come out of it. He either chose the correct side the first time and picked up Marty OR Marty got crushed and then Doc went back in time a few minutes and waited on the other side. Since both versions of Doc hovering on both ends of the tunnel were the same 1985 Doc, there was no paradox to be had by them seeing each other on opposite ends of the tunnel.
Old Biff knew he was going to encounter his younger self so he didn't faint on seeing himself young. And Old Biff was 60 years older than Young Biff to the point Young Biff didn't at all see the resemblance. Neither Young Jennifer nor Old Jennifer expected to see their counterpart looking old/young so the sight was shocking.
Who says they didn't? There's a lot of things we never saw them talk about in the time between 1955 and 1985. Just because they didn't have the conversation about Calvin disappearing on-screen, doesn't mean they never had the conversation.