Circular orb sighting at close range (about 25 feet) that moved in a straight line floating above the ground

A neighborhood friend and I were sitting on the edge of the Garage roof at dusk when we witness the UFO.  We had climbed up on the roof using a large tree at the rear of the garage. We were sitting side by side at the edge of the roof facing south when we both saw a circular glowing Orb move in a perfect straight line roughly from the preachers home to the back of the garage where the tree was located and we heard leaves rustling. My friend and I were in disbelief of what we had seen as we turned and looked at each other. My friend who was a few years older than me got up and ran franticly to the moveable basketball hoop located at the front of the garage and climbed down. I then got up and did the same thing. We were both very scared as we thought it was going to come up the tree. After a few minutes when we calmed down we went to the back of the garage where the tree was located and looked for it and found nothing. At the time I was about 8-9 years old and! the year was about 1976-1977 and now at the age of 43 I decided to document the event as I still to this day wonder what it was. Some years after the sighting I considered that it could be ball lightning but there were no thunderstorms in the area. All I can say about it was it moved in a perfect straight line moving at about 15 to 25MPH and was about 1 to 2 feet off the ground. It was circle orb in appearance and did glow but I don’t recall it being super bright…more like a dim to whitish medium glow. Unfortunately, my neighborhood friend who was the one on the roof with me past away years ago so I cannot consult with him on this.
For my professional background I am a laser engineer and manager.
Witness indicates that the date of the sighting is approximate.  PD