A sighting of four bright objects seen performing unusual maneuvers with no apparent change in speed.

The four objects of medium luminosity were observed travelling at an undetermined height - but definitely greater than 10,000 feet in line abreast formation with uniform spacing between the objects.  It is impossible to determine their speed other than that they appeared to be travelling more quickly than a commercial airliner, but their speed was constant.  After traveling roughly 1/2 of the way across the visible sky, the formation instanteously changed to a diamond formation with no apparent change in the speed of any of the objects.  It was almost magical, in that it changed literally in the blink of an eye.  After travelling approximately 2/3 of the way across the visible sky the formation again instantaeously changed, this time into a line with the space between the objects considerably diminished.  As soon as this line was formed, in order each of the objects described a semicircular path with the first going right, the second left, third right, and fourth left. With the completion of the maneuver, the objects ended up in a line identical to the one observed just before the maneuver began.  As soon as the line formed, the objects again instantaneously shifted to a line abreast formation, and contined until I could no longer observe the objects.  Thoughout the entire process, with the exception of the semicircular maneuver (at which they appeared to move more rapidly) was there any change in the apparent speed of the objects.  As an enthusiast of military and sporting aviation, I can categorically state that no military or commercial aircraft that I am aware of can make the types of manuevers made by these objects.  During the entire event there was no sound associated with the passage of these objects.