Movie series show that Dr. Emmett Brown can adjust time machine to go a somewhat selectable/quantized time in future or past.

Especially "today but exactly N years ago" quote seems to be showing a calculation of earth orbit around sun so it doesn't pop out in space after the journey.

Question: what is giving that car, the power of computing of N years of earth orbit to make it "land" in the same XYZ space(and surface) coordinates, within just the time of acceleration from 0 to 88 mph (1 minute?)?

Earth is not only moving around sun, but its rotating too! Same XYZ coordinate may not be same after exact N years! I mean 1 year is not exact multiple of 1 day. And in N years, even earth rotation could change some milimeters per second. Add the gravity effect of unknown celectial bodies orbiting sun, it would be a lot harder to compute.

Even if its possible, what about people? Very lucky that not a single human was harmed after time travel landing. They could have killed some people with delorean car.

Maybe flux-capacitor is a super computing neural network that computes time-space travel trajectory such that it always lands on asphalt(or desert sands) at the same height?

  • @Valorum actually I'm asking not "how", but "who does". Is there a 4096-CPU super computer inside of car? GPU was not evolved at that time. Commented Feb 10, 2017 at 0:57
  • backtothefuture.wikia.com/wiki/Spatial_displacement
    – Valorum
    Commented Feb 10, 2017 at 1:00
  • Earth's rotation isn't even the biggest problem. youtube.com/watch?v=zBlAGGzup48
    – Valorum
    Commented Feb 10, 2017 at 1:01
  • @Valorum then its simply moving galaxies and group of galaxies and whatever that has them back to original positions at the same time. Or with each timestep, universe is replicated, it moves on those replicas, jumping one by one until finds true time Commented Feb 10, 2017 at 1:07
  • Wasn't it something to do with the flux capacitor? I seem to recall reading something that said this was the thing that made time travel possible. (Can't remember where, I'll have to look further).
    – NiceOrc
    Commented Feb 10, 2017 at 1:33

1 Answer 1


No computations are necessary to arrive in the same place.

When a time-traveling object is supposed to appear "in the same place" at a different time, what place should that be? Elsewhere on the spinning earth? Elsewhere along the Earth's orbit? Elsewhere along the solar system's orbit around the galaxy? Elsewhere along the galaxy's orbit through the local group? Where relative to all matter in the universe should it appear?

You are making the mistake of assuming a universal frame of reference. There is no such thing. There are no stationary points in space. There are only relative frames of reference. So when referring to "the same place", that can only mean the same place relative to the dominant gravity well, which is exactly what the movie (and virtually all time travel stories) depict.

No spatial computations are necessary to keep a parked Delorean from flying off in to space. Earth's gravity does that perfectly well enough. So no spatial computations are necessary to keep a time-traveling Delorean in Hill Valley.

  • 1
    Funny enough I was just going to ask on meta whether I should ask and answer a generic form of the underlying question since I've seen it come up several times now.
    – J Doe
    Commented Feb 10, 2017 at 1:45
  • I also answered this question here: scifi.stackexchange.com/questions/123779/…
    – J Doe
    Commented Feb 10, 2017 at 1:49
  • Moon's gravity maybe? 0.01-0.02 mm? Commented Feb 10, 2017 at 2:17
  • 2
    Thanks for breaking my brain. I'll be back in three days once I've recovered.
    – Möoz
    Commented Feb 10, 2017 at 2:48

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