I am a very practal person I have never before this encounter seen anything I couldn't explain. I was driving an 18 wheeler across the Navada desert at around 24:00 hours. The moon was so bright I didn't need my headlights. I noticed some lights to my right moving my way. I watched the lights move toward me. I just thought it was a helicopter. I had the truck window down and begin to realize I couldn't hear any noise and the lights were moving closer. Curious I pulled over and stoped the truck. The lights were getting quite close by now and I still couldn't hear any noise. So I turned the motor off and called to my wife who was sleeping in the sleeper. I got out of the truck and realized that craft was directly above me. The craft set motionlessly about 20 feet above me. The craft was cicular in shape and the edges were curved up like a ball. It was about 100 feet in diameter. The bottom of the craft was made up of hugh metal sheets that looked like they had been exposed to supreme heat. The craft set directly above me for about 5 minutes. The hugh craft hovering silently above me was to much I begin to get scared. As I started to get back in the truck the craft started to move away. As I said before the moon was so bright I could see for miles in the open desert. The craft started moving and within seconds was out of sight. All of this was done without the slightest sound. Unforunatly my wife didn't wake up fast enought to see the craft.