Just curious to know what will be the time difference between someone living on the outer layer of our galaxy and us, considering the known facts that
- Time is relative to gravity
- Our sun goes around at 483,000 miles/hour(792,000 km/hr) to complete its galactic year
- Star systems at outer layer travel faster than ours due to Dark Matter and Dark Energy - couldn't find speed of those star systems though!
We can assume that both (Solar system and outer layer of star system) are on the same side of the galaxy.
EDIT: In order to re-phrase this question more clearly, as per Joan.bdm, it is related to time dilation - what is the aging rate difference if we left one of two twins on the Earth and the other one on a planet at outskirts of the Milky Way. Conversely, what is aging rate difference between closer to center of our galaxy and us?