I was doing archeogical work in the Badlands of North Dakota. The night was pleasant but tent was stuffy so friend and I took our sleeping bags outside. The moon was full and the sky was full of stars because we were far from cities and the sky was very clear. We were talking about our work and our lives and staring up at the sky. I noticed a very bright round object that seemed to be just below and slightly to the right of the moon. It wasn't moving. I thought that it might be a planet or a satellite because it didn't twinkle like a star. I pointed it out to my friend, who was also looking at it. It abruptly moved very fast to our right, then stopped again. We were baffled as to what could do that. Once again it moved fast at a 90 degree angle from its previous path and went out of sight. We weren't sure if it had been lit then the light turned off, or if it had moved too far away for us to see. We weren't afraid, just curious and baffled. We talked about it for a while but had no conclusions. (And we had not been drinking or anything.) this was before there were cellphones and the cameras were in the tent, although at the time we didn't think of photographing it. There is (and was) an air force ba north and east of where we were. When we got back to our field base a few days later we called the base and asked if they'd had aircraft out or had picked up anything on radar, after telling them what we'd seen. They basically told us we must have been hallucinating and that there was nothing there. My friend and I have discussed it since then, still wondering, and occasionally I dream about it. It was very clear, large (appeared about one-tenth the size of the moon but we didn't know how far it was from us or the moon) and very very bright. It was round, like the moon, and I couldnt be sure if it was reflecting light or emitting it. It did seem brighter than the full moon. I haven't seen anything like it since then, but I will never forget it. It was cometely silent.