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In the movie Contact, at around the 1 hour 20 minute mark, Palmer and Ellie are having a conversation about Einstein's theory of relativity. Palmer confirms with Ellie that if the machine works and she travels to Vega at anywhere near the speed of light, she would age only four years in the round-trip journey, whereas 50 years would pass on Earth.

However, later in the movie, when Ellie actually does make the journey, she is gone for 18 hours (as implied by the amount of static recorded by her headset), while only a split second passes on Earth. Isn't this the opposite of what was stated earlier? Shouldn't much more time have passed on Earth? I'm confused.

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    Yes, it is backwards, but the relativity stuff isn't there to solve the problem - it can't, and that's kind of the point. The time skip discrepancy adds more weight to Clarkes third law
    – DavidS
    Apr 25, 2016 at 16:40
  • Also, as I recall, she wasn't gone for anywhere near 18 hours from her time either. She basically got there and talked with her Dad (or aliens represented by him, or God, or however you want to interpret that) for no more than 20 minutes or so. Of course, they could've skipped a lot because nobody wants to watch an 18+ hour movie. Is it implied that she experienced that much time while she was gone? Or is what we saw in the movie supposed to be the whole trip in real time?
    – Darrel Hoffman
    Apr 25, 2016 at 21:26
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    @DarrelHoffman It is implied near the end of the movie that Ellie spent 18 hours away. We find this out in Rachel Constantine's video conversation with Michael Kitz after an investigating committee has apparently analyzed the mission data. Rachel says, "The fact that [Arroway's video unit] recorded static isn't what interests me. What interests me is that it recorded approximately eighteen hours of it."
    – Brian Rogers
    Apr 25, 2016 at 22:15
  • @BrianRogers - Yes, but that doesn't mean that Ellie experienced 18 hours of time, only that the video recorder did. With all that time dilation going on, who knows how that would affect a video recorder? It certainly didn't seem like they were trying to imply that she experienced almost a whole day's worth of time while she was gone. I do think this question may be unanswerable however, as the ambiguity was clearly deliberate.
    – Darrel Hoffman
    Apr 25, 2016 at 22:31
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    @DarrelHoffman Well, the recorder was on Ellie's head the entire time, so it would have been in the same frame of reference as her, and thus experienced the same amount of time as she did. In any case, I think the answers below cover more or less what I was asking. I'll leave the question open a while longer, then select one to accept. All have been upvoted by me.
    – Brian Rogers
    Apr 25, 2016 at 22:46

3 Answers 3

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To be very specific to the question, no, they didn't "get Relatively wrong" per se, they intentionally thwarted our expectations based upon our understanding of Relativity as a plot device.

The conversation between Palmer and Ellie is used to set the expectations of the audience, that if Ellie successfully travels anywhere outside of our Solar System in a timespan we can fit inside a movie, she'll be leaving the Earth she knows and the people on it behind, and many decades (at least) will have passed by the time she gets back. When the opposite occurs at the end of the movie, when she experiences time dilation "in reverse" as it were, it's used as a reason to completely discredit her story and leave both the in-world population and the audience hanging on what really happened - was her experience genuine or was it some sort of stress hallucination brought on by the intense forces at work on her body? Because all the science we know indicates that if she had gone anywhere, we'd be the ones waiting.

They are very intentional about understanding what is suggested by Relativity and circumventing it to accomplish two main goals:

  • Double down on the enmity between Bureaucracy (personified by James Woods) and Knowledge - in this case, showing the government going so far as to use scientific principles (Relativity) to hide the in-movie truth (that we can circumvent the limits we believe to be imposed by Relativity, and this alien tech is the evidence)
  • Enliven a sense of wonder and imagination at what could be that we don't know yet

The rational explanations for how she would have accomplished her trip, wormholes, etc, are less important to the movie than why she did it. The other answers do a good job of explaining the how, I hope this helps to understand the why.

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Note that it seems to involve FTL travel and also travel through a wormhole. Thus it would not involve travel "near the speed of light" which is completely in the physical universe. Travel within the current laws of relativity would mean that the traveler goes through less time than the resting framework.

One possible rationalization could be:

The ends of the wormhole lead to a specific place in time and space. The time passing between worm hole openings would not necessarily have anything to do with the coordinates of the end points. Thus the "time" of the return tube may actually be 18 hours earlier than the entry of the original worm hole on Earth. Enter at time T. get to destination at time T1 (using wormhole 1). Enter return wormhole (wormhole 2 - totally separate) at T1 + 18. Exit at T2 which happens to be T + a few seconds. T, T1, and T2 seem to be completely independent or may be (T+18)-18 happens to be the exit from wormhole 2.

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    @anaranjada The ends of the wormhole lead to a specific place in time and space. The time passing between worm hole openings would not necessarily have anything to do with the coordinates of the end points. Thus the "time" of the return tube may actually be 18 hours earlier than the entry of the original worm hole on Earth. Enter at time T. get to destination at time T1. Enter return wormhole at T1 + 18. Exit at T2 which happens to be T + a few seconds. T, T1, and T2 seem to be completely independent or may be (T+18)-18
    – sabbahillel
    Apr 25, 2016 at 17:05
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    @anaranjada, whether or not wormholes exist, a black hole is not one half of one. If you enter a black hole, the only place you're going is the center.
    – Ray
    Apr 25, 2016 at 21:39
  • @anaranjada, I assumed as much. My point was that while there do exist solutions to GR that permit white holes, I'm fairly certain that these are only in really odd geometries that are unlikely to correspond to anything in reality. By contrast, there's quite a bit of evidence that regular black holes actually exist. Granted, I'm no physicist, so it's possible that I'm misunderstanding something, or that there's recent evidence I'm unaware of, but to the best of my knowledge, white holes are things that are theoretically possible, but that few if any physicists believe to be real.
    – Ray
    Apr 25, 2016 at 21:55
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The wormholes in the movie effectively allow the pod to travel faster than light. It's complicated, but by traveling back and forth through wormholes that allow one to "beat light", one can actually return to a point in time before one left. Causality breaks down if Special Relativity holds true and faster-than-light travel is possible.

So, if aliens are able to build these wormholes, then they are undoubtedly skilled enough to do the math and to plot a course of travel where one could return to a point a split second after one left by traveling backwards in time just enough to cover the time spent -- in this case, eighteen hours.

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  • Wormholes do allow for "effectively" faster than light travel (you can beat light that travels outside the wormhole), but you're still moving "locally" slower than light (as measured in a 'local inertial frame' on a small patch of spacetime around you), so this isn't quite the same true FTL. In particular, wormhole travel doesn't necessarily cause causality violations, only if you move the two mouths into a particular configuration could this happen, and the chronology protection conjecture says they might be destroyed first.
    – Hypnosifl
    Apr 25, 2016 at 21:00
  • @Hypnosifl - I'm saying the aliens did this by design, so they would necessarily set up the route the cause the effect that ultimately occurs.
    – John Sensebe
    Apr 25, 2016 at 21:44

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