Theoretically speaking, this is not consistant, because if you move through one portal, you need to come out at another time through [another] portal. This would all happen faster than light, in a subreality which you cannot set up another portal. You would first need to move through spacetime, set up two portals, lightyears away, only then can you move through one portal, and hope to come out of the other end, which is also another seperate portal.
Instead, you could leave one end of a portal beside a quark-star for a few hundred years until it has been warped by the gravitational effects long enough, that one end has aged lots more than the other. Then you could jump in one end and come out the other, either in the past or the future.
That would take i calculate, to the one the most distant galaxies, 50,000 years... that the third cloest neighbouring galaxy, i think. By that time, we will probably be able to reach something called the Planck Energy and create wormholes... but they would be useless without the discovery of exotic matter.
Maybe not. It really depends on the circumstances. I know that superluminal suggested a theory that aliens don't experience relativistic effects, but this really wouldn't make sense, since quantum physics states that it rules over all space and time. But inflation when it cooled down, would have left vast area's of spacetime moving at different speeds... some galaxies then are moving relative to us at near light speed... so one can assume that we live in a relatively slow part of the universe. Aliens could use that kind of natural speed to reach us in 100's of years or so. They may have even increadible lifespans. We already know of creatures on earth, like the tortoise that can live hundreds of years.
UFOs are using a different form of energy than what you will find in current physics books. Go to this website and read about a theory on ufo propulsion and possible design to make it work. http://www.maxpages.com/ufoexplanation
