White globe above river at prehistoric indian site

I was 20 yrs. old at the time and driving west on hwy 96w 5 miles west of Franklin,TN. I saw a light through the trees to my right(north) and stopped on the Harpeth River Bridge. This is a rural area and back then there was almost no other traffic. It was night time. I'm really unclear as to the month or day of the month, but there were no leaves on the trees and it was warm because I was in a convertible Corvette with the top down. I turned off my headlights and walked to the guard rail and focused on the light which I had seen through the trees. I was looking northeast and saw that the light was a crisply defined, pure white globe about 30 feet above the river and moving at south west toward me and following the course of the river. It was moving at a speed of less than 5 mph and less than 100 feet from me. I could have thrown a rock and hit it. It was only about 4 feet in diameter. I knew right away that this was not a naturally occurring phenomena, but was an object made by some being. I assumed immediatetly I was in the presence of an alien craft. I stood there and decided to raise my right hand and WAVED! at it with a goofy smile on my face. It came a few feet closer to me and then changed direction and headed to the northwest away from me, lifted over the line of trees 300 feet from me, and  went back down behind them and I was no longer able to see it. I will always believe it changed direction because whatever very small entity inside it saw me standing there on the bridge with my hand in the air. I guess I am one of a small number who suprised a UFO. I drove around the area the rest of the night, but saw no more of the object and never reported it, but I think about it often as it changed my life. No one will ever convince me that I did not see something from another world or another time. Whatever it was, it was very interested in the river itself as it was following the course of the river exactly until it saw me. This is an area that was inhabited by prehistoric indians and ! there are 3 indian mounds south of the bridge within sight of the location so I have wondered over the years if the pilot of the craft was doing a little historical research, but of course I have no way of knowing. It made no sound whatsoever and there was no wavering in its movement. It moved as steadily as if it was on a track and never changed its speed at all. What struck me the most was that it was moving toward me and then instantly away from me with no change in speed. I forgot to mention that it was as bright as a street light and the light was coming from within the object.
Time and date are approximate.  PD