Wow. I don't have any answer to that.
IF you were in a spaceship, way out in interstellar space, how would you know how fast you were going?
What immovable point would you measure from?
If you left the Earth at , say, 100,000mph and exited our galaxy, would you still be going 100,000 mph?
(oops) I meant to quote your comment from post 40.
It must be late. Or, I’ve gone past the edge of the known universe.