Blue light in the sky appears and vanishes instantly.I was with some friends hanging out in my truck just parked, we were talking about what we did that day when I heard a huge "BANG" noise. At the same time that I heard the noise I saw a huge blue light in the shape of a circle. It was as if it were an explosion, starting from the center, it expanded outwards and then back to the center. All the lights in the street had turned off including my dashboard on the truck. That's when I knew something was wrong. I was in so much shock, I asked my friends if they saw it. It was four of us and only one other had seen it along with me. That's when I knew it wasn't a joke and what I saw was real. It was far up in the sky which is why I know it had something to do with UFO's and wasn't anything caused by humans.