100' dia metalic craft hovered 50 feet overhead for 30 min, rotating colored lights on bottom

Craft shrouded at first in a dark cloud despite clear sky, was observable only when cloud parted. Observer age 15, playing with others on athletic field, was physically affected on sighting such that his body's motion was retarded and sense of time was distorted. Craft made no sound. Craft hovered motionless approx 50 feet overhead for approx 30 min. Craft approx 100 feet in diameter, metalic gray in color; had yellow, red, and blue lights that rotated around the bottom of craft. Only the bottom was seen. Craft suddenly ascended vertically very rapidly and its shape seemed to turn spherical. Observer felt that occupants of craft were aware of him. There were others on the playground at the time who claimed not to see the craft.