explorerSG1

In its most simplified definition allowed: it may not or may be UFOs.  The lighting could be trickery of lighting reflection off an object, or our visualization of it giving false ideas or shape of the object.  Or the object's action that seem to defy logical explanation to what we currently know exist.  Yet it may truly be an UFO whose truth is only known by them and sought by some people who witness what cannot be explained but as possibly UFOs.