Special relativity and the Lorentz contraction

Imagine for a moment that we live in a world where the velocity of light is small, say 20 ms^-1 (nearly 45 m.p.h.). Then the predictions of the theory of special relativity would become much more obvious.

If we stood at a street corner in this strange world and watched traffic passing by, then all the cars would appear shortened and even people would appear a little thinner than they were when standing still.

If you put a friend in a shopping trolley and tried to push a trolley along, not only would it seem to get thinner (as observed by a person watching you go by) but you would also find that as you went faster and faster the trolley would seem heavier and heavier and so become more difficult to accelerate.