2006-04-07 - Sacramento, CA - Light

Bright light at low altitude vanishes leaving a round cloud

I am 50 years old and left Reno, NV 5:30am to Sacramento, CA to take a test. Some where in the Sierra's on interstate 80 there was a bright light, about 2000ft AGL. Looked to large, bright and still to be an Aircraft(Aircraft lights this close usaully show some transmited vibration). The light projected a flat and fanned-out beam into a cloud. Unlike a head light beam. I thought the cloud was causing this affect. After studying it for about a minute trying to justify it in my mind it then moved to the right and stopped. It dimmed and brightened then disappeared. As it disappeared there was a faint round fog or cloud like that which is generated by a high altitude jet engine but very faint. It formed a ball around where the light pushing out then rushed slightly into where the light was. The light going out and the cloud forming took about a second. I continued to watch the round cloud and noticed the other could was gone. As I watched the round cloud still trying to rationalize what I saw the round cloud disipated in about 5-7 seconds. It was a clear sky and only some of the brightest stars were still visible. Being a novice pilot and watching stars as a pass-time I can only say this is something I can't explain.