“They (distance and time) vary according to the rate of relative velocity between two observers.”
That is, they behave as components of a single phenomenon. They adjust in such a way that they always add up to the same total. When one is a particular value, the other will adjust accordingly. Therefore they are intimately linked.
(sorry, you may have to zoom your browser out in order to see the whole animated graphic. Or find and click on the earlier link. For some reason, it appears much smaller there)
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(SNIP)
"I want you to imagine that youve got a clock, only instead of having a clock where a gear turns and the hands move, you have a clock where a single photon of light bounces up-and-down between two mirrors. If your clock is at rest, you see the photon bouncing up-and-down, and the seconds pass as normal. But if your clock is moving, and you look on it, how will the seconds pass, now?
A light clock moving close to the speed of light will appear to run slower relative to an observer at rest. Image credit: John D. Norton, via http://www.pitt.edu/~jdnorton/teaching/HPS_0410/chapters/Special_relativity_clocks_rods/.
Quite clearly, it takes longer for the bounces to occur if the speed of light is always a constant. If time ran at the same rate for everyone, everywhere and under all conditions, then wed see the speed of light be arbitrarily fast the faster something moved. And whats even worse, is if something moved very quickly and then turned on a flashlight in the opposite direction, wed see that light barely move at all: itd be almost at rest.
Since light doesnt do this or change its speed-in-a-vacuum under any circumstances we know this naive picture is wrong.
Fascinating