time travel.

[altezon]

i also think if it is going to work it would have to be along the theory of spacial displacement. where a space from one place is swapped with the space of another.

What about potential differences in momentum ?

Elaborate please.

Someone correct me if I'm wrong, but consider the complicated motion of any point on earth at any given time. It's rotating with the planet, which would give it an angular velocity of anywhere from zero to 1000 mph, depending on the latitude. Imagine this point tracing out the circles of a spinning planet as earth moves along its orbit about the sun at an average velocity of 66 thousand mph. The earth's axis is tilted, so the circles are weaving in and out of the orbital plane like a corkscrew. It's an elliptical orbit, so the earth will be moving faster or slower depending on what month of the year it is, and it will also be constantly changing direction as it "falls" toward the sun. So the speed and direction of the departing time traveler will be varying a lot with the latitude, time of day, and month of of the year. Likewise, the speed and direction of the spacetime point he's going to will depend on the same factors.

If we're talking about short hops of a year or so, then maybe we can disregard everthing but the planetary motions relative to the sun. But we'd still have potentially enormous differences in momentum between objects occupying different placetimes. The time traveler could peacefully depart while at rest with respect to his original surroundings and arrive moving at several hundred miles an hour relative to his new surroundings. This could be inconvenient if something were in his way.

For longer trips the problem is perhaps much worse because the larger picture becomes significant. Earth is precessing like a wobbling top while orbiting the sun. The sun is bobbing up and down with respect to the galactic plane (taking its collection of planets with it) while also orbiting the galactic center. Actually, our whole solar system is tilted with respect to the galactic plane, which is why the Milky Way crosses the night sky athwart the ecliptic like a windshield wiper. So the earth's orbit about the sun is a corkscrew path along the direction of the sun's galactic orbit. Our galaxy is moving toward the Andromeda galaxy at 300 km/sec., while the Local Group to which they both belong has its own speed and direction in the cosmos.