asterisk8 said:
As a lifelong fan of astrophysics, and having contemplated the vastness of space quite a lot, I think it's entirely unlikely that that is a galaxy at the end of ESB. I understand that Star Wars rarely, if ever, obeys the laws of physics, so this is just for the sake of providing some insight and I think adywan is thinking along the same lines, so maybe this avoids him having to elaborate.
I've often felt that only the worst space fiction treats galaxies like countries or planets one can easily hop between. For all intents and purposes, this galaxy we live in IS the universe. Even after we achieve faster-than-light travel, we will likely never leave our galaxy. Even at 100 times the speed of light, it would take 1,000 years to cross the Milky Way. Talking about the distance between galaxies, even at 1 million times the speed of light, it would take 2 full year to get to the nearest galaxy.
It is simply unlikely, even with the most advanced technology one can dream of, even with wormholes, that lifeforms are capable of leaving their own galaxy.
In ESB Piett stated that if the Falcon had jumped to lightspeed "they'd be on the other side of the galaxy by now" mere minutes after the Falcon has disappeared from the Empire's scopes. If SW space travel is this fast then they could easily travel outside the galaxy.
However that assumes that the technology and science of SW is internally logically consistent. It is not. That's why using scientific theory to decide on a point of debate in SW is doomed to failure. This is Star Wars, not 2001 a Space Odyssey.
Note: At the speed of light. To travel any distance takes NO time at all. This is a consequence of special relativity. The universe in the direction of travel is lorentz contracted to a length of zero. Therefore you can traverse this distance in no time. Another way to look at it is that to people observing the craft from outside, time is lorentz slowed to the point at which it stops on board the ship. To those people the ship will appear to be travelling a vast distance at the speed of light. But if they could look at the pilots watch they would see that it had stopped.
So to travel 1000 light years at the speed of light. The journey for the occupants of the ship will be instantaneous (plus some time for acceleration and deceleration). For those watching from mission control it will take exactly 1000 years (plus the time to accelerate and decelerate).
So if (big if) we ever manage to develop light speed travel, mankind can explore the universe not just our local galaxy. However when they get back the earth will probably have been destroyed by the sun going nova. Time will pass at the normal rate for those left on earth.