No, if I was traveling with it, it would not appear shorter to me. So, you're saying that distance is the constant. OK, I can see that, since the speed of light is a constant, and that is measured in distance. I guess it all depends on the definition of distance. If it is between two points in the universe, it is constant only in a static (non-moving) universe, because in an expanding universe, all points move away from each other. If you use the speed of light as the yardstick, an expanding universe does not affect distance, as it is measured by the distance light travels in one second of time. Getting closer?
Yes and no.
if I was traveling with it, it would not appear shorter to me.
Keeeee-rect!
So, you're saying that distance is the constant.
Buzz! Wrong. The yardstick is shorter to someone outside your reference (not sharing your velocity/direction). Now, which length of the yardstick is "true"? The 24 inch one I see you holding while I'm sitting on this rock, or the 36 inch one you see in your hand as you zoom past me? It depends: the "true" distance of the stick is relative to the observer's reference. because in an expanding universe, all points move away from each other.
Oh, it's worse than that. You (and I) are on the surface of a planet rotating at a rate of 1,000 miles/hr, moving 20 miles a second around the sun which is moving 13 miles a second within our local star cluster which is moving within the Milky Way galaxy at 200 mi/sec, and the Milky way is moving - with respect to remote galaxies 100 mi/sec. All of the motions are in different directions.
Now, assume there are yardsticks throughout the universe. Likely not very many that are "objectively" the same length as yours.
If you use the speed of light as the yardstick…
Tis the only one ya got for everybody actually. Which led Herr Einstein to take this thought train in the beginning ( the beginning measuring time from our reference of course…) And that's your next clue.
Distance is relative (just ask any woman). You already said time was relative (but your explanation was off.)
You should have enough clues to get to 2 and-a-half right?