Stuck On The Sidewalk

I was walking down Broadway one day -- there is plenty of foot traffic going both ways on this sidewalk -- and the person coming towards me yawned.    Yawns are contagious of course, when someone yawns we want to yawn ourselves.  In fact it's hard not to yawn while writing this.  (Ooops, i just did!)

So the person walking towards me yawned, and then of course as they passed me, i yawned too.  But by then the next person walking southbound was in view, and she saw me yawn and by the time i passed her, she was yawning. 

There was another person walking a few feet behind me who must have seen her yawn.

It occurred to me that the yawn was stuck in one place on the sidewalk with people moving past it both ways.   The people were just the medium that supported the yawn, like the water in a river holding a log against a rock.  As long as the flow of people continued, the yawn would be stuck in that spot!