The Twins Paradox and the speed of light

Twin Paradox Revisited Sans Rocket-ships.SciFi's Assumption: Mystical magical aliens have some sort of FTL or FTL-like travel. Specifically some means from getting from interstellar point A to B 'instantaneously'. In SciFi this 'solves the problem' for SciFi authors and audiences, but would it actually work?Acceleration isn't limited to spaceships and visitation takes time, so wouldn't the twins paradox still be in play since those objects (earth and the alien home-world) are under the influence of different bodies in different gravitational fields?While I presume this comes into play within our own galaxy, I think it might be easier to use an example of aliens from a different galaxies. If aliens from galaxy A (a galaxy not in our local group) somehow managed to arrive on Earth instantaneously, and if galaxy A and galaxy B are hurdling away from each other, it seems to me that time would pass at a different rate on the alien planet than on Earth.

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.

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Starting Point:

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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.

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I'd like to hold off on the degree of those effects until you're in agreement that we have a workable starting point.

Let's try this another way. Forget twins, space travel, aliens, and time-travel.We build a space station orbiting the Earth. A child is born on the Earth and another on this space station at the exact moment. Due to the child in the space station under less gravitation it ages and experiences time at a slightly lesser rare. Am I correct?

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Not quite - it's the twin on Earth that ages more slowly than the twin on the space-station. There will also be a relative-velocity time dilation which will work to reduce the difference.

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Ah, right. I said it backwards. Okay let's shift back to aliens, but this time aliens who have no ability to time or space travel.As one point of reference we have Earth a one-G world on the other point we have the aliens who we'll also assume for now exist on a one-G world.My understanding here is that given both planets are one-G worlds that only acceleration would cause any significant time dilation, is this correct?Under what variables, if ever, would the time dilation effect be significantly great enough in this two planet scenario? Would we have worlds in our own galaxy which would experience time very much faster than we ourselves experience? Do we ever get scenarios along the line of a day is equal to a year or more?

Thanks Cavediver,If we cannot get a large 'to us' time shift within our own galaxy under the conditions I set forth, what about between planets each in galaxies somewhat far apart? Would say galaxies 100,000 light years be sufficiently far apart from each other to be accelerating fast enough away from each other to be effectively rocket ships. What amount of time dilation might occur then (keeping the idea that each planet is 1-G).

Thanks. This was an aspect I hadn't seen address before, so while it seems like it applies, it really isn't significant enough to matter.