They don’t have to send the widget to T-5 from T, they can send it to T-5 at T+30, or whatever.
The evil professor tries to force the grandfather paradox by refusing to send the widget back after it has already appeared. This causes the universe to start falling apart. A ragtag team has to steal the widget and get their own time machine working before electron mass changes and the electricity to power the time machine fails. At T+118 they send the widget back, resolving the paradox and saving the universe.
BTTF doesn’t make any sense. It’s more fantasy than science fiction. For example the 2015 Marty goes to in 2 should be either he a future where Marty and Doc and Jennifer disappeared 30 years earlier or one where their 2015 selves remember the adventure And know what will happen. What we got makes nonsense at all. Still a fun movie but makes no sense.
A recent comic I read about time travel solved all these issues by saying there is only one timeline. You can’t change the past because everything you are about to do in the past has already happened full stop.
“There is no problem with changing the course of history—the course of history does not change because it all fits together like a jigsaw. All the important changes have happened before the things they were supposed to change and it all sorts itself out in the end.”
– Douglas Adams, The Restaurant at the End of the Universe
Kage Baker uses this in her “Company” series of books. You can’t “alter the past”, but she points out, we really don’t know all that much about “the past”. 99.99999+% of history is never recorded, so who’s to say what happened? Sure, we can’t kill Hitler, because we know we didn’t kill Hitler, but we can pretty safely kill some random dude in 56BC, because who knows what happened to that guy?
True, as long as the blue widget is sent back at some point from an unspecified future to the point in the past where it had appeared, all is probably well. But what would happen if the widget is never sent back? I don’t know if it would be so dramatic as the universe falling apart; maybe the past would just get altered so that the experiment never happened after all. But what is the ‘grace period’ in which the widget can be sent back without affecting the sent-back widget past- an extra hour? A day? A year?
My whole original point was, time travel to the past does not seem to make sense unless one postulates an alternate branching timeline created at the moment the item appears in the past.
Sleight of hand. An identical widget was ready ahead of time, and slipped onto the platform at T-5. Perhaps using a cup to cover the platform was a poor idea.
Whatever is necessary for dramatic affect, unfortunately. Then justify that time limit with in universe rules.
I do agree, fictionalized time travel does not make much sense, so it really comes down to whether it is used to tell a satisfying story, and are the rules around it at least consistent enough in the story to get out of their own way, and not cause the audience to groan.
I think certain physics stuff says there’s no reason time needs to run forwards; it could run backwards. That is different from saying you can jump around to arbitrary positions in time. We know we can use speed to adjust the duration of a second, from an external reference frame. So a GPS satellite experiences time somewhat slower than an earth based atomic clock. The satellite isn’t jumping ahead to some random point in the future.
He didn’t say he thought the plot was or wasn’t on target. He was saying that compared to other time travel movies, this one got more things right than the others. The biggest glaring error in all of them, according to Tyson, is that they don’t take into account earth rotation and orbit, which means the likelihood of Marty arriving in the same spot he departed from were nil. He had a better chance of ending up in the ocean or floating somewhere in space.
That only works for stories structured that way. BTTF has Doc putting on a bullet proof vest, and the courthouse now has a visible chunk taken out of the ledge, that was not missing in the opening scenes.
This is how I feel the Terminator film series works.
The first (original) time line: Skynet is created, someone named John Connor destroyed it. Sarah is not his father. She is not hunted down, but dies in the nukular holocaust. We never see this timeline. At the very end, Skynet sends a terminator back in time, but this creates a new timeline.
(The Terminator) At the second the terminator appears, a new time line (2) is created The first is gone, never existed. (Whether this timeline continued on with a dead Sarah and no John, but was was replaced with timeline 3 when Kyle appeared, sine they both came from the same future, we don’t know. But, probably. It “never existed” itself as soon as Kyle landed, so it’s a moot point. I leave that to the tech folk. )
Kyle fathers a kid named John (not the first timeline John) defeats the terminator, and dies. We are now in a new timeline, Judgement day is not certain, and most likely won’t happen on Aug 29, 1997.
(Terminator 2) Cyberdine systems gains possession of the terminator’s arm and CPU, reverse engineers it, accidentally creates Skynet, which launches Judgement day, kills everyone, Sarah’s son John leads the resistance, destroys Skynet, but not before Skynet (who probably doesn’t actually understand time travel, and most certainly doesn’t know it “already” tried this (in a lost timeline)) send the T100 back to kill a youth John. (Good ideas always find a way). So this John, who probably doesn’t know anyone named Kyle Reese, sends a T101 back to protect himself.
This creates timeline 4, “never happening” timeline 3. Since this time the terminators are destroyed, and the CPUs and research are destroyed, the future may be safe.
(Terminator 3) But somehow someone invents the systems that become Skynet. Maybe someone in the government actually believes all these stories of time traveling machines, and says, hey, let’s see if we can do that. (good ideas find a way). So there is Judgement day, again. Skynet wins. Somehow, this John defeats it. Again. We never see this timeline, except for the couple minutes at the end of T2.
Skynet sends a terminator back to kill John (not realizing this is the third “time” they did), thus creating timeline 5, “never happening” timeline 4. But this time, the good terminator is just sent to minimize the damage.
By the time we get to the Sarah Connor Chronicles, we have time travelers from multiple futures fighting in the past. And technically, they ALL come from “never existed” futures. We might be up to timeline 15 by now. And the others are all gone, “never existed”. Poor Sarah, with the scooter and the pink waitress outfit, who can;t even balance a checkbok? She’s been “never existed” for quite some time.
I’ve always said, the best time travel movie is Bill and Ted’s Excellent adventure. No glaring paradoxes, but they do use time travel in ways others don’t. “We need you dad’s keys to get through that locked door. Okay, when we get back, we steal you dad’s keys and hide them … behind this sign!” Then they grab the keys from behind the sign, and get on with the plot.
The really neat part is, prior to that, his dad complains several times about how his keys are missing.
Alternate theory: it doesn’t take “time” (I understand exactly what you mean) for the change to propagate. Instead, what we are seeing is a representation of the “thought-driven quantum reality” effect. That is, reality is determined by what human consciousness thinks is right. To wit: whether the damned cat is alive or dead doesn’t depend on quantum equations, but on whether you believe it is alive or dead.
And this applies to time travel. As soon as Marty appears in the past, the timeline is threatened. Just being there could (and most certainly did) create any number of small changes that may “ripple” through to the Future, or be dampened by the “weight” of time. The longer he stays in the past, the higher the chances of creating a future different that existed when he left increases. This is manifested by the disappearing of the children, in age order, from his photo. It’s a representation of the quantum state equations. The longer George and Lorraine don’t get together, the higher percentage that the future will be different. But it isn’t different “yet”, until human actions have “locked down” the timeline. There’s still a chance Marty could be born but maybe Dave and/or Linda might not.
When Marty forces the future to lock in, the picture (and his own existence) revert.
What we don’t see is, there should be changes to the photo that even Marty might not notice. (I think the filmmakers missed an opportunity by not changing one of the kids’ shirts). Because, as we see, Marty didn’t restore the original timeline, he sort of patched it. Which is why he has cool parents and a new truck.
One time travel thing I’ve seen quite a bit in movies and TV, but can’t think of an immediate example, is where time travel is just like travelling to a different country - and where there is still a sense that events are still unfolding in the time you departed, at the same time as in the time you travelled to.
This means that, even though you have a time machine, there’s some sort of weird urgency because you have to get back before something runs out, back in the future. You apparently can’t just travel back to the moment you left - if you spend an hour in the past, an hour has somehow also passed in the timeframe you departed.
Explicit in the movie - when he first arrives in the '50s, he crashes into and knocks over a pine tree. This changes the name of the mall in his future, from Twin Pines Mall, to Lone Pine Mall.
Responding to a post on this topic from the other thread:
We know for a fact that “cool” Marty was still friends with Doc, because at the end of the movie, we see that Marty get in the Delorean and disappear after Doc gets shot. How they ended up friends is, almost certainly, vastly different from how they ended up friends in the original timeline, but it’s not impossible for it to have happened. Particularly since Doc knows he and Marty are going to be friends in the future, and can take steps to make sure he’s in Marty’s life somehow to make sure that happens.
One explanation for this I’ve seen somewhere is that time is a helix - and you can only travel to a location that is directly opposite you in the helix. This means when you go back to your side of the helix, exactly the same amount of time has expired there as on your side of the spiral.
I’m sure I’ve seen this in some old-time science-fiction story or other - maybe someone on this board remembers it. Or maybe there are numerous examples of this trope.
Back to the Future got one and only one thing right about time travel, but maybe that one thing is the most important: They realized what kind of movie they were making, and put in the amount of thought, and expected their audience to put in the amount of thought, appropriate for a silly comedy. End result, it’s a fun movie. It falls apart the moment you try to put any thought into it, so don’t do that.
As far as which one did the best job with the time travel, my pick is 12 Monkeys.
There was an episode of the 1954 Flash Gordon TV show that did this. “We have 24 hours to locate the bomb!” To which I kept replying, “No, you idiot, you have a thousand years to locate the bomb! Take your time, and do it right!”
One of Piers Anthony’s Xanth novels did this. A wizard/mad scientist/sage character gave a long explanation for it. A supporting character translated, “You might miss by a century, but not by a day.”
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