While traveling through space, is there an up or down or side-to-side to the universe?
"Simply put, "Down" will always be the direction that has the greatest gravitational pull. "Simply put, "Down" will always be the direction that has the greatest gravitational pull. When that is not immediately apparent, then down is observational and opinionative based on the individual. Overall it would be irrelevant in space and not used as directional guidance other than to discern the difference between the ceiling and the floor (if these are defined).