I’d say that using the tracks and a rocket of some kind makes more sense than trying to get a steam engine up to those speeds. Or, one of them could have gotten behind the car and kept shouting FUS RO DAH! until it got up to 88mph…
-XT
Actually, I had thought that getting five miles of wire rope would be prohibitive in 1885 California, but there were dozens of miles of wire rope in California, possibly even hundreds of miles, and much of it in chunks that were literally miles long and plenty strong enough-- in the cable car system in San Francisco! Now, the Doc may not be able to get his hands on any in short order, but it’s not out of the question technologically. Does anyone know where Hill Valley is supposed to be, exactly?
From the Libyans, duh. 
I think the most obvious solution is go in the mine and put a note in the car that says “bring extra gas”.
Or just say that in the note delivered by the law firm.
A second note, and there may not be time to arrange it, but the last two suggestions are a real plot killer. 
If it’s so easy to kill a plot then maybe it’s time to rethink the plot.
Hey, I love the BTTF movies and I wouldn’t change a thing, but picking plot holes is fun. 
True, but the only solution I have for those two ideas is turning it into *Bill and Ted’s Excellent Adventure. *
Marty doesn’t rip the fuel line until after he’s already gone back to 1885. There’s no one to leave the note for.
You’re not thinking 4 dimensionally.
Darn you!
Of course I am. This isn’t Bill and Ted. You can’t think “I’ll just put a note in the Delorean to bring extra gas” and then find the can sitting there when you get to the car.
Why not?
It wouldn’t happen exactly like that, of course. It would change the whole sequence of events. Marty would arrive in the old west aware of the second note and carrying the gas. They wouldn’t remember the previous sequence of events.
I’ll grant that it would be difficult to depict that clearly in a movie.
Because the BTTF movies don’t use that style of time travel (conversely, the Bill & Ted movies do). What happens, happened. You can only make changes if you yourself have a time machine or there’s a second time traveler somewhere else in time (and with access to the Delorean).
Doc sent the Fed Ex letter in an 1885 where Marty never came back (because he was still in 1955). By coming back, Marty has created 1885A and any note they leave would appear in the Delorean in 1955A, left for a Marty that has already taken the Delorean back to the original 1885.
Or, in the words of the Doc:
[QUOTE=Doc Brown]
Here. Here, let me demonstrate. Let’s say that this line represents time.[draws straight line and points to places] Here’s the present 1985, the future and the past. Obviously, somewhere in the past the timeline skewed down into this tangent creating an alternate 1985. Alternate to you, me, and Einstein, but reality for everyone else. Recognize this? It’s the bag the sports book came in; I know because the receipt was still inside.
[/QUOTE]
[QUOTE=Doc Brown, later]
We can’t, because if we travel into the future from this point in time, it will be the future of THIS reality, in which Biff is corrupt, powerful, and married to your mother, and in which THIS has happened to ME!! No, our only chance to repair the present is in the past, at the point where the time line skewed into this tangent. In order to put the universe back as we remember it and get back to our reality, we have to find out the exact date and specific circumstances of how, when, and where young Biff got his hands on that sports almanac.
[/QUOTE]
I’m thinking…and it hurts.
There’s a more solid reason that leaving a note to bring more gas in the DeLorean won’t work. You’re up against temporal hysteresis.
The timeline resists change. The effects of a change propagate slowly, while a reversion propagates quickly. I could go into more detail on the apparent properties of this phenomenon, but the relevant factors here are that it takes time for a change to affect the time traveler who caused it and that it takes more time to affect someone from farther ahead in the timeline. The obvious example is Marty’s older siblings being erased before Marty himself was affected. That was a propagation across roughly 15 years, assuming Marty began to fade when the change wave reached his birth date, and it took about a week.
The change wave emanating from placing a note in the DeLorean would have to propagate across 70 years. It’s a narrow wave, so it should propagate faster than the one Marty triggered by shoving his father out of the street, but it’s got nearly five times as far to go, and they have less than a week. It’s highly unlikely that the wave will arrive in time for the gas can to have been in the DeLorean before Doc (or Marty) gets shot.
It’s possible that when the change wave finally did arrive, it would retroactively negate the death, but is that a chance you’d really want to take?
This is a great point! In the BTTF-verse, time changes take time to propagate through, well, time, as demonstrated by the picture in the first movie. However, consider the second movie, where newspaper headlines changed in a matter of seconds. Again, we have a 1985 artifact in 1955, but in these instances the changes happen nearly instantaneously. Surely those newspaper headlines weren’t drastically less important (i.e., narrower waves) than Marty’s family picture?
It’s not about importance. Its about certainty. Gradual changes were things that still had a chance of turning out one way or another. Instantaneous changes were things that were now 100% certain. Probability waves!
If you mean the newspaper clippings they took from alt-1985 to 1955 with them, that’s a case of reversion. As I said, reversions always seem to propagate faster than changes, though it’s possible that they slow down once a new timeline is sufficiently established. Marty’s photo, Doc’s tombstone, the newspaper clippings–they all revert almost instantly.
It’s still a valid point when looking at alt-1985, though, where 2015-Biff’s changes are in effect. There were signs everywhere that the change wave had already passed, and they were visible as soon as the time travelers arrived–Marty noticed that bars had appeared on the windows at Jennifer’s house.
This raises a good question. Why had 1985 already been alt-1985 when Doc, Marty, Jennifer, and Einstein arrived in it?
There is a different factor involved: in this case, the time travelers underwent a temporal displacement after the changes were made, but before they were personally affected by them. Time travel itself seems to offer some form of insulation against change; time travelers can fade, if a change results in them having never been displaced, but their memories don’t change. Marty didn’t forget his siblings as they vanished from the photo, and he didn’t remember his new and improved family when he got back to the future.
Time travel appears subjectively to be effectively instantaneous, but if the time vehicle is dissociated from the time stream during travel, would the travelers perceive any passage of time? What if the vehicle can’t reenter the time stream at a point that is in flux? Since 1985 was already changing, they were stuck in a timeless limbo until all the changes to alt-1985 were complete. They avoided fading by leaving 2015 before the wave reached them and waiting it out in a “place” where it couldn’t reach them, at the cost of arriving in a time when it had already done its worst.
This isn’t actually the only time we see this; the ending of the first movie shows the same effect. Marty saw the outcome of one of his last changes to 1955 within minutes of his arrival in 1985–Doc’s survival of the Libyan attack. That could conceivably be explained by the fact that the note triggered a very narrow wave*; it had no effect on the timeline at all until Doc bought the vest, and that would be a very minor effect until he actually wore it while getting shot. Maybe that would allow the wave to reach 1985 in time.
That doesn’t account for the major changes to Marty’s family, though. Their attitudes, status, jobs, and all had changed completely when Marty first encountered them after his return. From his perspective, that was only hours after the triggering events (George slugging Biff and shoving the guy on the dance floor), and the wave was not so narrow, since it had been causing changes since 1955 and had been spreading faster since around 1963 (Dave McFly’s presumed birth year). My hypothesis is that between departing 1955 and returning to 1985, Marty was in a sort of temporal holding pattern until the timeline stabilized.
Imagine if 1955-Doc had found a way to power the flux capacitor other than waiting for the lightning strike, and Marty had gone back to 1985 without fixing the mess with his parents. Would he have found himself existing in a world that had never known him? Perhaps his father had gone off to college and never married. Maybe his mother–with neither George nor “Calvin” to fixate on–married someone else (or drank herself to death at an early age). Even Doc would only remember him from 1955 (assuming he survived the Libyans), and might be rather suspicious of him, since his memory of events wouldn’t match any description Marty gave him in 1955 of their friendship in the 1980s.
Potential counterexamples to the hypothesis: The change wave had not reached 2015 when 2015-Biff returned, and it’s possible to interpret 2015-Biff’s behavior on his return as symptoms of fading (which, as a side note, might suggest that the wealthy alt-Biff was actually dead by 2015). Why was 2015-Biff able to return to a 2015 that had not yet changed, and why might he have been fading despite having time traveled after making his change to history?
My handwavium supply is getting low, but I can scrape up enough to manage a possible explanation. The displacement from 1955 to 2015 was long enough that 2015 was not yet in flux. 2015-Biff was able to return to an unchanged 2015 because 2015 was still unchanged. If he actually was fading in that scene, he must have slipped in right ahead of the wave’s leading edge, leaving him vulnerable to its effects. The nature of the trigger event–2015-Biff directly interacting with 1955-Biff–means that he would be the first thing to change, and the other time travelers had plenty of time to leave the time stream before they were affected.
*For reference, my description of the waves as “narrow” or “wide” doesn’t precisely match up to either importance or certainty. It’s based on the scope of the changes. A taped-together note sitting in a pile of papers in a box for 30 years, having no effect other than minutely increasing the weight of the pile, would correspond to a very narrow wave. When that note causes Doc to buy a bulletproof vest, the wave spreads slightly due to add-on effects like the seller having a bit more money, which might cause them to engage in slightly different actions, like going out to dinner and thereby affecting other people in small ways. When the vest keeps Doc alive so that he can go on affecting the lives of other people, the wave spreads a great deal. Many of the changes in Marty’s life–and, by extension, the lives of Jennifer, their children, and some of the people they interact with–between 1985 and 2015 are really the result of that note, so by 2015, the wave triggered by planting the note on Doc is very wide indeed.