I remembered things that I used to observe when I was very young about five years old, six, or seven years old, and my parents would take me to parades, say, the Macy's Day Parade in New York, which was a big thing in around, around Thanksgiving time, sort of, the lead up to Christmas shopping. To whip people into a frenzy for shopping. With big balloons, and a spectacular parade. So I would rush to the front of the line, and wiggle through people's legs and sit as close as I could to these huge balloons that were going by, and for an hour, I would watch the balloons go by, and at the end, when the last balloon had gone by, the last parade sweeper-upper had swept up, I would look down at the asphalt pavement and be delighted to discover that the asphalt was oozing in the opposite direction to the way the balloons were going. So if the balloons had been going left to right, I'd look at the asphalt and the asphalt would be oozing right to left. And the first time I saw this, my eyes were popping out, and I tried to look to where to the oozing was coming from, and, as you might expect, that was also oozing in the same direction. And then: where was it going? And that was oozing in the same direction. And then, after fifteen, twenty seconds, thirty seconds or so, it would disappear and the asphalt was solid. So, it was clear to me, even as a five year old, that this was an illusion, that the asphalt was not really oozing but it was some trick that was being played on me somehow.

And, thinking about it, I began to piece together the idea that if the balloons were going that way, it would go in the other direction. And, of course, later on, I discovered that this is a well-known psychological effect. It's official name is 'the waterfall effect', because you can produce the same thing if you hike somewhere and then look at a waterfall, and look at it for a minute, and then switch your gaze to the canyon wall, here, it will seem to be flowing in the opposite direction to the waterfall. So, it's something to do with the way the eye and the mind perceive motion. And then, here, it's a reaction against that.