Very much in the middle of nowhere in Michigan's Upper Peninsula (henceforth called the UP) is a "mysterious" light that appears every night along old US 45 between Paulding and Watersmeet. It was first recorded being sighted in the 1960s, and has since been photographed and videotaped numerous times, and was even investigated by Syfy's show Fact or Faked, whose findings were inconclusive.
The folklore explanations are variations on a theme: someone was killed and now you see his ghost wandering the woods in the form of a bright light of shifting hue. The more scientific explanation is that people are just seeing headlights from the distant highway. I am by no means declaring this is a "ghost light," but the headlights theory has me slightly skeptical mostly because it is in the middle of freaking nowhere. The light is almost constant, and while driving out there at dusk, we saw almost no other cars. Kimmy was freaking out because it was so deserted.
Though the distant highway and some trickery of refraction and reflection could account for some of the current light reports, it most certainly doesn't explain the numerous accounts of the people viewing with us who have seen the light come within 50 feet of the current viewing area, or who drove miles further down the track in their youth, parked on a bridge that is now washed out, and had the light come right up to their cars.
There are a number of hills between where we stood watching and where current US 45 intercepts the line of sight. When we walked down the track in an attempt to get closer, we lost sight of the light because a hill was in the way. If there is a hill blocking the view of the distant highway, how could people of the past have still seen the headlights? Headlights also haven't always been as bright as they are now.
The reason this stretch of woods is so clear is because there is a strip of power lines that go for many miles. People there told us that they have seen the light "dancing along" the power lines. Possibly ball lightening? Though the light is said to appear only on clear nights, I can't say what the weather was doing the previous times these folks were out. Another few stories reported to us that night swore the light came right up to the viewing area and "looked just like a train coming right at you."
If the light is not supernatural in nature (which it entirely may not be), my guess is there is no one explanation for its appearance, nor, in that case, one precise light. A number of factors could be producing lights that observers then interpret to be one and the same. Perhaps this kind of thing goes on all the time in the wilds of the UP, or anywhere, for that matter, this one just happens to be well known and relatively easy to get to, causing an audience to flock to it every night.
Or maybe it's the ghost of some unaccounted for railroad worker stuck in the middle of the forest for eternity messing with us all. You decide!
(In memory of my father David R. Coburn, Sept 2, 1952 - Oct 21, 2010. I miss you every day, Pa.)