Driving almost due south through an isolated and heavily wooded section of N. wisconsin, sky was comlpetely clear with visibility at not less than 20 miles, objects approached from east and lit the forest brightly enough to cast shadows of trees across road before spheres themselves became visible, three craft in a loose group then crossed opening in skyline about 90 degrees wide at an angle of elevation from my perspective of about 30 degrees and at at an estimated distance of around 1000-1200 yards, their size was such that the shape was perfectly discernable, color was translucent appearing emerald green, they were followed 2-3 seconds later by a single sphere identical to the first, my astonished remarks at the first sighting woke the two persons riding with me in time for one of them to see the fourth object, and both observed the surreal lighting cast over the entire landscape as it diminished. Objects were moving at near mach 1 or only slightly less (I am a pilot) and made no sound, flight path was straight and level to slightly ascending. The intensity of light radiating would easily have been in the multi millions of lumen, and had a purity I have only seen in the prismatic seperation of sunlight. On entering the town of Spooner about 15 minutes later and stopping for fuel,(a local policeman had to get keys and reopen a service station) the few people we spoke to had not seen anything unusual. In 40 years of flying including three years in combat I have seen nothing remotely similar, the sight was so unusual I remember it now as if it were last week.