LogFAQs > #963135415

JimBeamMeUp posted...

Even if you jumped just a few minutes the point in time space has moved considerably. Depending on which side of the planet you were on relative to it's orbit around the sun, you'd either have the misfortune of popping out several miles into the Earth's interior or several miles above it, and that's not even taking into account the movement of the entire solar system within the milky way, or the movement of the entire milky way within the local group, etc.

Yep. The earth orbits the sun at ~30 km/s, which is in turn is flying through space at ~370 km/s (it orbits the centre of the Milky Way, but its orbital period is ~226 million years, so we can simplify it as linear motion on the time scale of humanity's brief blip of existence), so depending on where the earth is in its orbit, it's going to move somewhere between 340 and 400 km for every second you travel through time, without you. Most fictional time travel either ignores this or comes up with some vaguely plausible explanation for why it's not an issue, but if you're attempting to travel only through time and not space, there's virtually zero chance of you ever ending up on the surface of the earth again, let alone in the spot you want.

As much as absolute coordinate systems are common in sci-fi, they really do not respect how dynamic celestial bodies really are. Even space itself is not static; there's really no absolute frame of reference from which to measure anything.