The recent availability of lightweight LED light strips has allowed pranksters with remote controlled aircraft to mimic UFO sightings with remarkable skill. Metafilter user smoothvirus put together an excellent post about this pranking, and its consequences.
If you are a devoted fan of the late lamented show MonsterQuest, you have already seen these light strips in action in several episodes. For example, in the "Ohio Grassman" episode, a local RC helicopter enthusiast is enlisted to help with the hunt. The team attaches a FLIR thermal camera to the belly of the RC helicopter. The pilot meanwhile attaches a set of lightweight LED strips to the helicopter itself, so that he can monitor its orientation when it is in flight in the darkness.
Of course, this is just the latest and most technologically advanced in a long line of UFO hoaxes. When I was but a wee lass growing up in Alaska, one week the city of Anchorage was treated to a nighttime display of floating multicolored lights which seemed to drift silently through the night sky.
The culprit turned out to be a thin sheet of plywood, with a black plastic garbage bag attached at the edges to serve as a balloon. Inside, the prankster had attached several cans of Sterno. Sterno both gives off heat and emits a flame which is colored oddly. The heat lifted the whole works into the sky, hot air balloon-style, and the light of the Sterno did the rest.
In January of 2009, a group of pranksters staged a UFO hoax over Morristown, N.J. simply by attaching flares to helium balloons with five feet of fishing line.
And of course there are the "actual mistake" category of UFO sightings. I myself once thought I had spotted some amazing UFO activity once, when I was staying at a relative's vacation home on Whidbey Island here in Washington. I watched, rooted to the spot, as a series of lights flashed in a slow pattern across the water.
After several minutes a commercial airliner passed over my head and eventually joined the other lights, which turned out to be the runway of Sea-Tac Airport, as viewed through a few gaps in a distant line of hills.
In fact, the easy availability and use of RC flying vehicles (including both airplanes and helicopters) plus the cheap and ready LED light strips, should mean that any low-flying light source can be automatically dismissed as a hoax. Particularly in an area with a known concentration of observers, like a city, town, suburb, or popular park.
All of which isn't to dismiss all UFO reports as hoaxes, of course. For example, reports of a dark triangular craft flying overhead in the remote Southwest desert eventually proved to be sightings of stealth aircraft being tested by the US military. But certainly, anyone observing supposed UFO footage (or a supposed UFO itself) should exercise extreme skepticism. And if you see a UFO composed of blue lights, you're almost certainly seeing one of these LED hoaxes.
Photo credit: Flickr/pommesschranke