Thanks Cavediver,
Let's consider the issue of 'alien visitors', but we'll use Earthlings visiting a planet far, far, away.
The first reason for being vague about the method of 'travel' is that I suspect that 'getting there is only part of the problem' while being actually here and away from the alien home world is part of the problem which gets ignored. I may certainly be completely mistaken on this idea, but the aspect of the problem I'd like to explore, is time dilation as relates to being a world far away from one's home world.
The second reason for being vague is that aliens being able to bypass time dilation isn't my own argument, but that of others (often circular and vague). In this one aspect of this problem I don't wish to explore the science (or non-science) of wormholes/stargates/astral-projection/tesseracts/FTL/probability-drives/etectera, but instead, explore just what actually happens to the visiting alien.
Still, let's set a 'techno-magic' solution and go from there. I'll pick 'stargates'. Further, for this discussion, we don't know how stargates work (they don't use wormholes, we can call it the Copperfield/Penn & Teller/Carrot-top Uncertainty Principle Bridge) we can only say that on exiting the 'stargate' somehow very little time has passed. Let's say under an minute. How would we know? Something along the lines of comparing current measurements against previous measurements and the departure time, visitation time, and return trip vs. time absent from the point of departure.
My assumption is in this thought-experiment (let's not call it an example) presumes the 'stargate' can account for all time dilation effects from traveling, but only from traveling and wouldn't compensate for being on a world far away from Earth.
So let me try spout some garbage here and see if you can massage it into shape.
quote:
Starting Point:
Even were aliens somehow able to compensate for or bypass time dilation effects to reach Earth, there are still time dilation effects apart from those traveling here which would needing to be addressed. Gravitation and cosmological expansion between where we are in the cosmos and where the aliens originate also creates time dilation.
I'd like to hold off on the degree of those effects until you're in agreement that we have a workable starting point.