This may be a tad off topic here, but I did see it outdoors. It was an interesting experience to say the least.
If you drive to Watersmeet Michigan, then head north up to the highway a few miles and turn left onto Robins Pond Road you will come to a guardrail. The guardrail is the end of the road, but the road used to dip down a little grassy hill and cross a creek, up, and back out to the highway in about two miles. A little bridge once spanned the creek, but was removed because of lack of maintainance.
If you go to this guardrail at dusk, night, or even on an overcast day you will see a small red light dancing back and forth on the opposite side of the gully. The light can be single, double, triple, and red, green, white, or yellow. It will swing back and forth, go up and down the hill (mabey 75 yards away), "dance" on the powerlines that follow the road, and even change colors and shape when people at the guardrail honk car horns or flash lights at it.
Some people claim it is car lights, but the light is too random and intelligent to be car lights. Also, the highway is obscured by two miles of hills and trees. Others claim it is the ghost of a conductor who was killed when a train traveling on the grade the road was later built on smashed into his stopped train. Others claim things like a ghost miner (they didn't use red lamps) or lumberjack, or a postman ambushed by indians there on his dogsled, or even the piezo-electric effect of quartz in the soil being agitated by microtremors being refracted through swamp gasses.
What ever it is, it will appear any night you go there. I have seen it four times so far in the course of five years. Once at night in the middle of a December blizzard, once at dusk in July, once on a cold clear night in the deep freeze of January, and once on a warm April evening. It is just a few miles north of Watersmeet Michigan, in the UP. The Lac Vieux Desert is another good reason to make the trip. I hear theres good fishing there.