system
Given the following post, respond as if you're commenting on Reddit:
human
[Back to the Future] Wouldn't the DeLorean need some kind of positioning/location device to account for the movement of the Milky Way?

I just watched BTTF and it dawned on me that if they went back to 1955 from the same location, wouldn't the Earth be somewhere else in the universe due to the movement of the Milky Way, causing Marty to wind up in the middle of space? Or even the Earths orbit might have an impact. Did the DeLorean have some feature to explain this or am I wrong and this wouldn't be an issue?
gpt
What no one seems to understand here is that there is no absolute metric from which everything else can measure it's position and velocity from.  That was proved back in 1887 by Michelson and Morley showed there was no luminiferous aether that matter traveled through.  This lack of absolute position of velocity was further cemented in 1905 with Einstein's Theory of Special Relativity which showed that the speed of light was the same from any reference frame.  Then Einstein's Theory of General Relativity in 1915 laid the framework for Emmet Brown to create the General Theory of Time (unpublished) which he used to then design the Tri-Flux Capacitor.

What Dr. Brown understood was that mass, energy, space, time, gravity, and velocity are *all* relative.  This enables the Tri-Flux Capacitor to warp space-time so that the worldline travelled by the Delorean intersects with its position in the past or future.  As it warps spacetime along the time dimension, the fold naturally follows the already-existing surface of the gravitational space-time Reimannian manifold, so that the Delorean doesn't have to account for motion like the rotation of the earth, movement of the earth around the sun, motion of the sun in the Milky Way, the motion of the Milky Way in our galactic local group, the motion of our local group compared to other galactic clusters, etc.  Since the fold naturally follows the already-existent geodesic, the worldline of the Delorean simply intersects at a different location along the geodesic manifold, so that the Delorean (and it's passengers) have effectively traveled through time *relative* to its surroundings.