While serving as a military pilot in West Germany(1969-1970),I lived in a high rise apartment building. Standing next to an open window, I observed a pure white ball, approximately the size of large grapefruit or small basketball, which entered my field of view on the left and flew without, hesitation - in a perfectly straight line - to my right without any making any sound, and then left my field of view. I estimate the speed at approximately 100 MPH, and I am sure of the size because the object passed between where I was and an adjacent building located 200 feet away. I could hear chilren playing below, and know the object made no sound.