In the opening scene of Back to the Future, Marty arrives at Doc's place to play guitar. After blowing himself across the room 🤣, Doc calls Marty on the phone. In the middle of the conversation, all the clocks strike 8:00 and start chiming. Then the following exchange takes place:

Doc: Are those my clocks I hear?
Marty: Yeah. Uh, it's 8:00.
Doc: Perfect! My experiment worked! They're all exactly 25 minutes slow!

Now up until re-watching the movie today, I have always taken Doc's response as just some throwaway line, like "What was he trying to test by setting all of his clocks back 25 minutes?". But as we can see in the opening scene, there are a lot of clues foreshadowing other events in the movie: the news report, the plutonium crate under the bed, the clock of the Harold Lloyd homage / Doc at the end of the movie, etc. Since this opening scene contains so many important clues, I'm wondering if Doc's response may also be a clue.

If so, what exactly is his "experiment"? Is the viewer meant to infer that Doc sent all of these clocks 25 minutes into the future? It doesn't completely track, so let me lay it out.

Why it tracks

  • We know Doc has been out of the house all week. From the same phone conversation:

Marty: Doc, what's goin' on? Where you been all week?
Doc: Workin'.

  • Doc would probably have wanted to test on something inanimate before testing on Einstein (and eventually himself) so he doesn't "disintegrate" him 🤣. This would contribute to the amount of time he's been working, and part of why he's been gone "all week".
  • Later that night, Doc sends Einstein and the DeLorean 1 minute into the future at 1:20am. When they reappear at 1:21am, Einstein's watch is exactly 1 minute behind because he skipped over that minute. So sending clocks 25 minutes into the future would mean that they are 25 minutes behind when they catch up to the present.
  • If he had indeed already sent the clocks into the future in the DeLorean, he knows the DeLorean will disappear at 88 mph ("If my calculations are correct, when this baby hits 88 mph, you're gonna see some serious shit!"). That is why he is confident to drive it directly at himself and not even flinch. In fact, he's so confident, Marty starts to move out of the way, but Doc pulls him back. (I believe the "if" in his statement, and keeping them both in front of the speeding car is purely to make him look crazy).
  • It may be a bit of a reach, but Doc initially plans to go 25 years into the future, so maybe the 25 minutes is a nod to that at a smaller scale.

Why it doesn't track

  • "Perfect! My experiment worked!" Doc says this with some amount of surprise in his voice. If he really sent the clocks into the future inside the DeLorean and they reappeared 25 minutes later, he would already know the experiment worked, so there's no reason for him to be surprised by it, let alone even mention the experiment to Marty. I guess the latter could be for exposition's sake, but the surprise in his voice doesn't make sense.
  • As soon as the car disappears "through" them, Doc looks intently at the remote control, as though he can't believe it worked. "What did I tell you! 88 miles per hour!!" It would make more sense for him to have said this staring directly at Marty or the camera instead of at the remote control.
  • "It's cold. Damn cold!" This is another first-time reaction. If he'd done it before, he'd already know the DeLorean would come back iced over. Although, I don't believe the icing-over is consistent throughout the whole trilogy, so I suppose it's possible that this was the first time it happened.

So what's the answer?

Is the "experiment" on his clocks that he actually sent them 25 minutes into the future, prior to testing on Einstein? Or is that a throwaway line, and it's something random that has no bearing on anything else?

  • 1
    It could be some other time-related experiment that's not time travel, but something to do with it. All we know is that the clocks are running behind. Taking a clock to a high mountain can also make that happen (though not by 25 minutes).
    – magarnicle
    Commented May 26, 2023 at 3:07
  • 2
    You have already answered your own question in question itself. Hope it makes sense.
    – Rahul
    Commented May 26, 2023 at 9:03
  • 1
    Also covered here: scifi.stackexchange.com/questions/56626/…
    – komodosp
    Commented May 26, 2023 at 10:55

1 Answer 1


We don't know

It's reasonable to assume that the film makers put this scene in to foreshadow the fact that some screwy things were going to happen with Time itself.

But even from a Watsonian point of view, it's also reasonable to assume there's a lot more science that goes into making a time machine than just getting a flux capacitor, sticking it in a DeLorean and driving it at 88 mph. For example, if you were to make a computer (from scratch, as Doc did with the time machine) you'd have to do all sorts of tests in labs on the various components, most of which wouldn't involve sticking them in a box and seeing how it looks on a monitor.

So it's not hard to imagine that there's some sort time-travel experiment to see if the clocks could venture 25 mins into the future over a course of a week, without putting them in the Delorean and sending them off at 88mph.

We never find out what it is, but at this point the movie is using it to build the intrigue, so it's probably best left unsaid, from an artistic point of view.

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