> what's the difference between 'universe expansion' and 'travel'? Travel happens inside the universe and expansion doesn't? If a rock is sliding along a stret

> what's the difference between 'universe expansion' and 'travel'? Travel happens inside the universe and expansion doesn't? If a rock is sliding along a stretchy sheet, stretching the sheet will make other things on the sheet move farther away from the rock, potentially faster than the fastest that the rock can slide, even though the rock doesn't move any faster.